* Re: [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory
2026-11-06 16:51 [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory Usama Arif
@ 2026-11-10 10:31 ` Kiryl Shutsemau
2026-11-10 10:39 ` Jinjie Ruan
2026-11-10 16:02 ` Bradley Morgan
2 siblings, 0 replies; 5+ messages in thread
From: Kiryl Shutsemau @ 2026-11-10 10:31 UTC (permalink / raw)
To: Usama Arif
Cc: Andrew Morton, baoquan.he, rppt, pasha.tatashin, pratyush,
ruirui.yang, corbet, skhan, rdunlap, muchun.song, osalvador,
david, jbohac, sourabhjain, ruanjinjie, leitao, linux-kernel,
kexec, linux-doc, linux-mm, hannes, riel, shakeel.butt, zaslonko,
brads, kernel-team
On Fri, Nov 06, 2026 at 08:51:42AM -0800, Usama Arif wrote:
> crashkernel=size,cma reserves a separate CMA pool. On systems that
> already reserve several gigabytes with hugetlb_cma= (which is common in
> the Meta fleet), the crash kernel cannot use that existing memory as
> part of its working set. With hugetlb_cma=6G, requesting another 2G
> with crashkernel=2G,cma brings the total CMA reservation to 8G, none of
> which can serve unmovable kernel allocations.
>
> Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> reserve dedicated CMA areas only for the remainder. With hugetlb_cma=6G,
> a 2G request reuses 2G without reserving more CMA. With hugetlb_cma=2G,
> a 4G request reuses 2G and reserves another 2G.
>
> The full HugeTLB CMA pool remains available to HugeTLB and movable
> allocations during normal operation. After a crash, the capture kernel
> can use the selected ranges as working memory. The conventional
> reservation is still required to hold the kernel image and initrd.
>
> The ,cma option already opts into excluding userspace memory from the
> vmcore. This includes allocated HugeTLB pages in the selected ranges,
> which the capture kernel can overwrite. The existing dump completeness
> and pending DMA risks apply to these ranges as well.
>
> Have architecture code record the requested CMA size and perform the
> reservation in mm_core_init_early(), immediately after
> hugetlb_cma_reserve(). The HugeTLB CMA areas are then available for reuse
> while memblock can still reserve any remainder.
>
> Use the existing four range slots for both reused and dedicated memory.
> Limit reused memory to the page-aligned request, account for dedicated
> CMA alignment, and report any shortfall. Ignore malformed optional sizes
> and reject requests that would overflow page rounding.
>
> Suggested-by: Breno Leitao <leitao@debian.org>
> Signed-off-by: Usama Arif <usama.arif@linux.dev>
> ---
> v1 -> v2:
> - Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> reserve dedicated CMA areas only for the remainder. (Kiryl)
Suggested-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
--
Kiryl Shutsemau / Kirill A. Shutemov
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory
2026-11-06 16:51 [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory Usama Arif
2026-11-10 10:31 ` Kiryl Shutsemau
@ 2026-11-10 10:39 ` Jinjie Ruan
2026-11-10 15:27 ` Usama Arif
2026-11-10 16:02 ` Bradley Morgan
2 siblings, 1 reply; 5+ messages in thread
From: Jinjie Ruan @ 2026-11-10 10:39 UTC (permalink / raw)
To: Usama Arif, Andrew Morton, baoquan.he, rppt, pasha.tatashin,
pratyush, ruirui.yang, corbet, skhan, rdunlap, muchun.song,
osalvador, david, jbohac, sourabhjain, leitao, linux-kernel,
kexec, linux-doc, linux-mm, kas, hannes, riel, shakeel.butt,
zaslonko, brads, kernel-team
在 2026/11/7 0:51, Usama Arif 写道:
> crashkernel=size,cma reserves a separate CMA pool. On systems that
> already reserve several gigabytes with hugetlb_cma= (which is common in
> the Meta fleet), the crash kernel cannot use that existing memory as
> part of its working set. With hugetlb_cma=6G, requesting another 2G
> with crashkernel=2G,cma brings the total CMA reservation to 8G, none of
> which can serve unmovable kernel allocations.
>
> Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> reserve dedicated CMA areas only for the remainder. With hugetlb_cma=6G,
> a 2G request reuses 2G without reserving more CMA. With hugetlb_cma=2G,
> a 4G request reuses 2G and reserves another 2G.
>
> The full HugeTLB CMA pool remains available to HugeTLB and movable
> allocations during normal operation. After a crash, the capture kernel
> can use the selected ranges as working memory. The conventional
> reservation is still required to hold the kernel image and initrd.
>
> The ,cma option already opts into excluding userspace memory from the
> vmcore. This includes allocated HugeTLB pages in the selected ranges,
> which the capture kernel can overwrite. The existing dump completeness
> and pending DMA risks apply to these ranges as well.
>
> Have architecture code record the requested CMA size and perform the
> reservation in mm_core_init_early(), immediately after
> hugetlb_cma_reserve(). The HugeTLB CMA areas are then available for reuse
> while memblock can still reserve any remainder.
>
> Use the existing four range slots for both reused and dedicated memory.
> Limit reused memory to the page-aligned request, account for dedicated
> CMA alignment, and report any shortfall. Ignore malformed optional sizes
> and reject requests that would overflow page rounding.
>
> Suggested-by: Breno Leitao <leitao@debian.org>
> Signed-off-by: Usama Arif <usama.arif@linux.dev>
> ---
> v1 -> v2:
> - Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> reserve dedicated CMA areas only for the remainder. (Kiryl)
> ---
> .../ABI/testing/sysfs-kernel-kexec-kdump | 3 ++
> Documentation/admin-guide/kdump/kdump.rst | 22 ++++++--
> .../admin-guide/kernel-parameters.txt | 16 +++++-
> arch/arm64/mm/init.c | 2 +-
> arch/powerpc/include/asm/kexec.h | 2 -
> arch/powerpc/kexec/core.c | 12 ++---
> arch/powerpc/mm/mem.c | 6 +--
> arch/riscv/mm/init.c | 2 +-
> arch/x86/kernel/setup.c | 2 +-
> include/linux/crash_reserve.h | 14 ++++-
> include/linux/hugetlb.h | 12 +++++
> kernel/crash_reserve.c | 51 ++++++++++++++-----
> mm/hugetlb_cma.c | 50 ++++++++++++++++++
> mm/mm_init.c | 2 +
> 14 files changed, 159 insertions(+), 37 deletions(-)
Should it be separated according to the architecture and framework code?
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
> index f59051b5d96d7..9197cbbcbe7c8 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
> +++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
> @@ -58,4 +58,7 @@ Description: read only
> the Contiguous Memory Allocator (CMA) area that are allocated
> to the crash (kdump) kernel. It lists the start and end physical
> addresses of CMA regions assigned for crashkernel use.
> + This includes existing HugeTLB CMA memory selected with
> + crashkernel=size,cma. These ranges remain usable
> + by the running kernel and are excluded from the vmcore.
> User: kdump service
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 7587caadbae1a..91779205d1456 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -313,9 +313,25 @@ crashkernel syntax
>
> 4) crashkernel=size,cma
>
> - Reserve additional crash kernel memory from CMA. This reservation is
> - usable by the first system's userspace memory and kernel movable
> - allocations (memory balloon, zswap). Pages allocated from this memory
> + Reserve additional crash kernel memory from CMA. Existing HugeTLB CMA
> + memory is used first, and dedicated CMA areas are reserved for any
> + remaining amount. For example, this reuses 2G from the existing 6G pool
> + without reserving additional CMA memory::
> +
> + hugetlb_cma=6G crashkernel=256M crashkernel=2G,cma
> +
> + With a smaller HugeTLB CMA pool, the remainder is reserved separately::
> +
> + hugetlb_cma=2G crashkernel=256M crashkernel=4G,cma
> +
> + This reuses the existing 2G and reserves another 2G of dedicated CMA.
> + Both kinds of area use the same limit of four physical ranges. If there
> + is insufficient memory or too few range slots, the kernel reports the
> + shortfall. Normal CMA alignment applies to dedicated reservations.
> +
> + The selected memory remains usable by the first system's userspace,
> + including HugeTLB allocations, and kernel movable allocations
> + (memory balloon, zswap). Pages allocated from this memory
> range will not be included in the vmcore so this should not be used if
> dumping of userspace memory is intended and it has to be expected that
> some movable kernel pages may be missing from the dump.
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 0b3c140babd94..a1fb40e500097 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1100,7 +1100,21 @@ Kernel parameters
> or memory reserved is below 4G.
> crashkernel=size[KMG],cma
> [KNL, X86, ARM64, RISCV, PPC] Reserve additional crash
> - kernel memory from CMA. This reservation is usable by
> + kernel memory from CMA. Existing hugetlb_cma memory is
> + used first, and dedicated CMA areas are reserved for any
> + remaining amount. For example:
> + hugetlb_cma=6G crashkernel=256M crashkernel=2G,cma
> + reuses 2G without reserving more CMA, while:
> + hugetlb_cma=2G crashkernel=256M crashkernel=4G,cma
> + reuses 2G and reserves another 2G of dedicated CMA.
> +
> + Both kinds of area use the same limit of four physical
> + ranges. If the available memory or range slots cannot
> + cover the requested size, the kernel reports the
> + shortfall. Normal CMA alignment applies to dedicated
> + reservations.
> +
> + The selected memory remains usable by
> the first system's userspace memory and kernel movable
> allocations (memory balloon, zswap). Pages allocated
> from this memory range will not be included in the vmcore
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 4e7682dfe366c..a781cc60b4282 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -114,7 +114,7 @@ static void __init arch_reserve_crashkernel(void)
> return;
>
> reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
> - reserve_crashkernel_cma(cma_size);
> + crashkernel_cma_set_size(cma_size);
> }
>
> static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
> diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
> index e02710d6a2e1a..d3b5028102cdd 100644
> --- a/arch/powerpc/include/asm/kexec.h
> +++ b/arch/powerpc/include/asm/kexec.h
> @@ -117,11 +117,9 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt, struct crash_mem
> #ifdef CONFIG_CRASH_RESERVE
> int __init overlaps_crashkernel(unsigned long start, unsigned long size);
> extern void arch_reserve_crashkernel(void);
> -extern void kdump_cma_reserve(void);
> #else
> static inline void arch_reserve_crashkernel(void) {}
> static inline int overlaps_crashkernel(unsigned long start, unsigned long size) { return 0; }
> -static inline void kdump_cma_reserve(void) { }
> #endif
>
> #if defined(CONFIG_CRASH_DUMP)
> diff --git a/arch/powerpc/kexec/core.c b/arch/powerpc/kexec/core.c
> index dc44f11be353e..1b70eb10beac2 100644
> --- a/arch/powerpc/kexec/core.c
> +++ b/arch/powerpc/kexec/core.c
> @@ -62,8 +62,6 @@ void machine_kexec(struct kimage *image)
>
> #ifdef CONFIG_CRASH_RESERVE
>
> -static unsigned long long crashk_cma_size;
> -
> static unsigned long long __init get_crash_base(unsigned long long crash_base)
> {
>
> @@ -107,6 +105,7 @@ static unsigned long long __init get_crash_base(unsigned long long crash_base)
> void __init arch_reserve_crashkernel(void)
> {
> unsigned long long crash_size, crash_base, crash_end;
> + unsigned long long cma_size = 0;
> unsigned long long kernel_start, kernel_size;
> unsigned long long total_mem_sz;
> int ret;
> @@ -115,7 +114,7 @@ void __init arch_reserve_crashkernel(void)
>
> /* use common parsing */
> ret = parse_crashkernel(boot_command_line, total_mem_sz, &crash_size,
> - &crash_base, NULL, &crashk_cma_size, NULL);
> + &crash_base, NULL, &cma_size, NULL);
>
> if (ret)
> return;
> @@ -133,12 +132,7 @@ void __init arch_reserve_crashkernel(void)
> }
>
> reserve_crashkernel_generic(crash_size, crash_base, 0, false);
> -}
> -
> -void __init kdump_cma_reserve(void)
> -{
> - if (crashk_cma_size)
> - reserve_crashkernel_cma(crashk_cma_size);
> + crashkernel_cma_set_size(cma_size);
> }
>
> int __init overlaps_crashkernel(unsigned long start, unsigned long size)
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index b617b69452cd6..d6e84dc1e24c5 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -272,12 +272,10 @@ void __init arch_mm_preinit(void)
> {
>
> /*
> - * Reserve large chunks of memory for use by CMA for kdump, fadump, KVM
> - * and hugetlb. These must be called after pageblock_order is
> - * initialised.
> + * Reserve large chunks of memory for use by CMA for fadump and KVM.
> + * These must be called after pageblock_order is initialised.
> */
> fadump_cma_init();
> - kdump_cma_reserve();
> kvm_cma_reserve();
>
> /*
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index e822fce0af4b0..194045dc3fed6 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1357,7 +1357,7 @@ static void __init arch_reserve_crashkernel(void)
> return;
>
> reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
> - reserve_crashkernel_cma(cma_size);
> + crashkernel_cma_set_size(cma_size);
> }
>
> void __init paging_init(void)
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 19fc8e1714e64..8848e207780b5 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -627,7 +627,7 @@ static void __init arch_reserve_crashkernel(void)
> }
>
> reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
> - reserve_crashkernel_cma(cma_size);
> + crashkernel_cma_set_size(cma_size);
> }
>
> static struct resource standard_io_resources[] = {
> diff --git a/include/linux/crash_reserve.h b/include/linux/crash_reserve.h
> index 30864d90d7f50..b11d7814979cc 100644
> --- a/include/linux/crash_reserve.h
> +++ b/include/linux/crash_reserve.h
> @@ -5,6 +5,7 @@
> #include <linux/linkage.h>
> #include <linux/elfcore.h>
> #include <linux/elf.h>
> +#include <linux/range.h>
> #ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
> #include <asm/crash_reserve.h>
> #endif
> @@ -31,7 +32,18 @@ int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
> unsigned long long *low_size, unsigned long long *cma_size,
> bool *high);
>
> -void __init reserve_crashkernel_cma(unsigned long long cma_size);
> +#if defined(CONFIG_CRASH_RESERVE) && defined(CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION)
> +void __init crashkernel_cma_set_size(unsigned long long size);
> +void __init reserve_crashkernel_cma(void);
> +#else
> +static inline void __init crashkernel_cma_set_size(unsigned long long size)
> +{
> +}
> +
> +static inline void __init reserve_crashkernel_cma(void)
> +{
> +}
> +#endif
>
> #ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
> #ifndef arch_add_crash_res_to_iomem
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 58f755e70e966..69732e4cc03e2 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -1349,12 +1349,24 @@ static inline spinlock_t *huge_pte_lock(struct hstate *h,
> return ptl;
> }
>
> +struct range;
> +
> #if defined(CONFIG_HUGETLB_PAGE) && defined(CONFIG_CMA)
> extern void __init hugetlb_cma_reserve(void);
> +unsigned long long __init
> +hugetlb_cma_add_crashkernel_ranges(unsigned long long size, struct range *ranges,
> + int *nr_ranges, int max_ranges);
> #else
> static inline __init void hugetlb_cma_reserve(void)
> {
> }
> +
> +static inline unsigned long long
> +hugetlb_cma_add_crashkernel_ranges(unsigned long long size, struct range *ranges,
> + int *nr_ranges, int max_ranges)
> +{
> + return 0;
> +}
> #endif
>
> #ifdef CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING
> diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
> index eee37a11380ce..53d76ba6b3c31 100644
> --- a/kernel/crash_reserve.c
> +++ b/kernel/crash_reserve.c
> @@ -16,6 +16,7 @@
> #include <linux/kmemleak.h>
> #include <linux/cma.h>
> #include <linux/crash_reserve.h>
> +#include <linux/hugetlb.h>
>
> #include <asm/page.h>
> #include <asm/sections.h>
> @@ -340,9 +341,9 @@ int __init parse_crashkernel(char *cmdline,
> * optional CMA reservation
> * cma_base is ignored
> */
> - if (cma_size)
> - __parse_crashkernel(cmdline, 0, cma_size,
> - &cma_base, suffix_tbl[SUFFIX_CMA]);
> + if (cma_size && __parse_crashkernel(cmdline, 0, cma_size,
> + &cma_base, suffix_tbl[SUFFIX_CMA]))
> + *cma_size = 0;
> #endif
> if (!*crash_size)
> ret = -EINVAL;
> @@ -470,21 +471,41 @@ void __init reserve_crashkernel_generic(unsigned long long crash_size,
> }
>
> struct range crashk_cma_ranges[CRASHKERNEL_CMA_RANGES_MAX];
> +static unsigned long long crashkernel_cma_size __initdata;
> +
> +void __init crashkernel_cma_set_size(unsigned long long cma_size)
> +{
> + crashkernel_cma_size = cma_size;
> +}
> +
> #ifdef CRASHKERNEL_CMA
> int crashk_cma_cnt;
> -void __init reserve_crashkernel_cma(unsigned long long cma_size)
> +void __init reserve_crashkernel_cma(void)
> {
> - unsigned long long request_size = roundup(cma_size, PAGE_SIZE);
> - unsigned long long reserved_size = 0;
> + unsigned long long cma_size = crashkernel_cma_size;
> + unsigned long long request_size, reserved_size, reused_size;
>
> - if (!cma_size)
> + if (!cma_size || crashk_res.start >= crashk_res.end)
> return;
>
> + if (cma_size > ULLONG_MAX - (PAGE_SIZE - 1)) {
> + pr_warn("crashkernel CMA size is too large\n");
> + return;
> + }
> + cma_size = roundup(cma_size, PAGE_SIZE);
> + reused_size = hugetlb_cma_add_crashkernel_ranges(cma_size,
> + crashk_cma_ranges,
> + &crashk_cma_cnt,
> + CRASHKERNEL_CMA_RANGES_MAX);
> + reserved_size = reused_size;
> + request_size = cma_size - reused_size;
> +
> while (cma_size > reserved_size &&
> crashk_cma_cnt < CRASHKERNEL_CMA_RANGES_MAX) {
>
> struct cma *res;
>
> + request_size = min(request_size, cma_size - reserved_size);
> if (cma_declare_contiguous(0, request_size, 0, 0, 0, false,
> "crashkernel", &res)) {
> /* reservation failed, try half-sized blocks */
> @@ -500,21 +521,23 @@ void __init reserve_crashkernel_cma(unsigned long long cma_size)
> crashk_cma_ranges[crashk_cma_cnt].start +
> cma_get_size(res) - 1;
> ++crashk_cma_cnt;
> - reserved_size += request_size;
> + reserved_size += cma_get_size(res);
> }
>
> if (cma_size > reserved_size)
> - pr_warn("crashkernel CMA reservation failed: %lld MB requested, %lld MB reserved in %d ranges\n",
> - cma_size >> 20, reserved_size >> 20, crashk_cma_cnt);
> + pr_warn("crashkernel CMA reservation failed: %llu MB requested, %llu MB reused, %llu MB newly reserved in %d ranges\n",
> + cma_size >> 20, reused_size >> 20,
> + (reserved_size - reused_size) >> 20, crashk_cma_cnt);
> else
> - pr_info("crashkernel CMA reserved: %lld MB in %d ranges\n",
> - reserved_size >> 20, crashk_cma_cnt);
> + pr_info("crashkernel CMA: %llu MB reused, %llu MB newly reserved in %d ranges\n",
> + reused_size >> 20, (reserved_size - reused_size) >> 20,
> + crashk_cma_cnt);
> }
>
> #else /* CRASHKERNEL_CMA */
> -void __init reserve_crashkernel_cma(unsigned long long cma_size)
> +void __init reserve_crashkernel_cma(void)
> {
> - if (cma_size)
> + if (crashkernel_cma_size)
> pr_warn("crashkernel CMA reservation not supported\n");
> }
> #endif
> diff --git a/mm/hugetlb_cma.c b/mm/hugetlb_cma.c
> index cd6a64986278a..cd6f64da31a2c 100644
> --- a/mm/hugetlb_cma.c
> +++ b/mm/hugetlb_cma.c
> @@ -11,6 +11,8 @@
> #include <linux/memblock.h>
> #include <linux/math.h>
> #include <linux/math64.h>
> +#include <linux/range.h>
> +#include "cma.h"
> #include "internal.h"
> #include "hugetlb_cma.h"
>
> @@ -387,6 +389,54 @@ void __init hugetlb_cma_reserve(void)
> hugetlb_cma_size = 0;
> }
>
> +/**
> + * hugetlb_cma_add_crashkernel_ranges - share HugeTLB CMA with the crash kernel
> + * @size: maximum number of bytes to share, aligned to PAGE_SIZE
> + * @ranges: crash kernel memory ranges
> + * @nr_ranges: number of entries already in @ranges, updated on return
> + * @max_ranges: capacity of @ranges
> + *
> + * The shared memory remains available to the HugeTLB allocator until a crash.
> + * Only physical ranges belonging to successfully reserved CMA areas are added.
> + *
> + * Return: number of bytes shared.
> + */
> +unsigned long long __init
> +hugetlb_cma_add_crashkernel_ranges(unsigned long long size, struct range *ranges,
> + int *nr_ranges, int max_ranges)
> +{
> + unsigned long long shared_size = 0;
> + int nid, i;
> +
> + for_each_node_mask(nid, hugetlb_bootmem_nodes) {
> + struct cma *cma = hugetlb_cma[nid];
> +
> + if (!cma)
> + continue;
> +
> + for (i = 0; i < cma->nranges; i++) {
> + struct cma_memrange *cmr = &cma->ranges[i];
> + unsigned long long range_size;
> + struct range *range;
> +
> + if (shared_size == size || *nr_ranges == max_ranges)
> + return shared_size;
> +
> + range_size = min_t(unsigned long long,
> + PFN_PHYS(cmr->count), size - shared_size);
> + range = &ranges[(*nr_ranges)++];
> + range->start = PFN_PHYS(cmr->base_pfn);
> + range->end = range->start + range_size - 1;
> + shared_size += range_size;
> +
> + /* Keep shared pages reserved if CMA activation fails. */
> + cma_reserve_pages_on_error(cma);
> + }
> + }
> +
> + return shared_size;
> +}
> +
> bool hugetlb_cma_exclusive_alloc(void)
> {
> return hugetlb_cma_only;
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index a9d848c92678b..2367af05570bd 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -28,6 +28,7 @@
> #include <linux/swap.h>
> #include <linux/cma.h>
> #include <linux/crash_dump.h>
> +#include <linux/crash_reserve.h>
> #include <linux/execmem.h>
> #include <linux/sizes.h>
> #include <linux/vmstat.h>
> @@ -2686,6 +2687,7 @@ void __init mm_core_init_early(void)
> free_area_init();
>
> hugetlb_cma_reserve();
> + reserve_crashkernel_cma();
> hugetlb_bootmem_alloc();
>
> sparse_init();
--
Best regards,
Jinjie
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory
2026-11-10 10:39 ` Jinjie Ruan
@ 2026-11-10 15:27 ` Usama Arif
0 siblings, 0 replies; 5+ messages in thread
From: Usama Arif @ 2026-11-10 15:27 UTC (permalink / raw)
To: Jinjie Ruan
Cc: Usama Arif, Andrew Morton, baoquan.he, rppt, pasha.tatashin,
pratyush, ruirui.yang, corbet, skhan, rdunlap, muchun.song,
osalvador, david, jbohac, sourabhjain, leitao, linux-kernel,
kexec, linux-doc, linux-mm, kas, hannes, riel, shakeel.butt,
zaslonko, brads, kernel-team
On Tue, 10 Nov 2026 18:39:34 +0800 Jinjie Ruan <ruanjinjie@huawei.com> wrote:
>
>
> 在 2026/11/7 0:51, Usama Arif 写道:
> > crashkernel=size,cma reserves a separate CMA pool. On systems that
> > already reserve several gigabytes with hugetlb_cma= (which is common in
> > the Meta fleet), the crash kernel cannot use that existing memory as
> > part of its working set. With hugetlb_cma=6G, requesting another 2G
> > with crashkernel=2G,cma brings the total CMA reservation to 8G, none of
> > which can serve unmovable kernel allocations.
> >
> > Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> > reserve dedicated CMA areas only for the remainder. With hugetlb_cma=6G,
> > a 2G request reuses 2G without reserving more CMA. With hugetlb_cma=2G,
> > a 4G request reuses 2G and reserves another 2G.
> >
> > The full HugeTLB CMA pool remains available to HugeTLB and movable
> > allocations during normal operation. After a crash, the capture kernel
> > can use the selected ranges as working memory. The conventional
> > reservation is still required to hold the kernel image and initrd.
> >
> > The ,cma option already opts into excluding userspace memory from the
> > vmcore. This includes allocated HugeTLB pages in the selected ranges,
> > which the capture kernel can overwrite. The existing dump completeness
> > and pending DMA risks apply to these ranges as well.
> >
> > Have architecture code record the requested CMA size and perform the
> > reservation in mm_core_init_early(), immediately after
> > hugetlb_cma_reserve(). The HugeTLB CMA areas are then available for reuse
> > while memblock can still reserve any remainder.
> >
> > Use the existing four range slots for both reused and dedicated memory.
> > Limit reused memory to the page-aligned request, account for dedicated
> > CMA alignment, and report any shortfall. Ignore malformed optional sizes
> > and reject requests that would overflow page rounding.
> >
> > Suggested-by: Breno Leitao <leitao@debian.org>
> > Signed-off-by: Usama Arif <usama.arif@linux.dev>
> > ---
> > v1 -> v2:
> > - Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> > reserve dedicated CMA areas only for the remainder. (Kiryl)
> > ---
> > .../ABI/testing/sysfs-kernel-kexec-kdump | 3 ++
> > Documentation/admin-guide/kdump/kdump.rst | 22 ++++++--
> > .../admin-guide/kernel-parameters.txt | 16 +++++-
> > arch/arm64/mm/init.c | 2 +-
> > arch/powerpc/include/asm/kexec.h | 2 -
> > arch/powerpc/kexec/core.c | 12 ++---
> > arch/powerpc/mm/mem.c | 6 +--
> > arch/riscv/mm/init.c | 2 +-
> > arch/x86/kernel/setup.c | 2 +-
> > include/linux/crash_reserve.h | 14 ++++-
> > include/linux/hugetlb.h | 12 +++++
> > kernel/crash_reserve.c | 51 ++++++++++++++-----
> > mm/hugetlb_cma.c | 50 ++++++++++++++++++
> > mm/mm_init.c | 2 +
> > 14 files changed, 159 insertions(+), 37 deletions(-)
>
> Should it be separated according to the architecture and framework code?
>
IMO, the commit and change ins small and simple enough that it doesnt need
to be separated into different commits.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory
2026-11-06 16:51 [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory Usama Arif
2026-11-10 10:31 ` Kiryl Shutsemau
2026-11-10 10:39 ` Jinjie Ruan
@ 2026-11-10 16:02 ` Bradley Morgan
2 siblings, 0 replies; 5+ messages in thread
From: Bradley Morgan @ 2026-11-10 16:02 UTC (permalink / raw)
To: usama.arif
Cc: akpm, baoquan.he, brads, corbet, david, hannes, jbohac, kas,
kernel-team, kexec, leitao, linux-doc, linux-kernel, linux-mm,
muchun.song, osalvador, pasha.tatashin, pratyush, rdunlap, riel,
rppt, ruanjinjie, ruirui.yang, shakeel.butt, skhan, sourabhjain,
zaslonko
On 6 November 2026 16:51:42 GMT, Usama Arif <usama.arif@linux.dev> wrote:
>crashkernel=size,cma reserves a separate CMA pool. On systems that
>already reserve several gigabytes with hugetlb_cma= (which is common in
>the Meta fleet), the crash kernel cannot use that existing memory as
>part of its working set. With hugetlb_cma=6G, requesting another 2G
>with crashkernel=2G,cma brings the total CMA reservation to 8G, none of
>which can serve unmovable kernel allocations.
>
>Use existing HugeTLB CMA memory first for crashkernel=size,cma and
>reserve dedicated CMA areas only for the remainder. With hugetlb_cma=6G,
>a 2G request reuses 2G without reserving more CMA. With hugetlb_cma=2G,
>a 4G request reuses 2G and reserves another 2G.
>
>The full HugeTLB CMA pool remains available to HugeTLB and movable
>allocations during normal operation. After a crash, the capture kernel
>can use the selected ranges as working memory. The conventional
>reservation is still required to hold the kernel image and initrd.
>
>The ,cma option already opts into excluding userspace memory from the
>vmcore. This includes allocated HugeTLB pages in the selected ranges,
>which the capture kernel can overwrite. The existing dump completeness
>and pending DMA risks apply to these ranges as well.
>
>Have architecture code record the requested CMA size and perform the
>reservation in mm_core_init_early(), immediately after
>hugetlb_cma_reserve(). The HugeTLB CMA areas are then available for reuse
>while memblock can still reserve any remainder.
>
>Use the existing four range slots for both reused and dedicated memory.
>Limit reused memory to the page-aligned request, account for dedicated
>CMA alignment, and report any shortfall. Ignore malformed optional sizes
>and reject requests that would overflow page rounding.
>
>Suggested-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Bradley Morgan <bradley.morgan@linux.dev>
>Signed-off-by: Usama Arif <usama.arif@linux.dev>
>---
>v1 -> v2:
>- Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> reserve dedicated CMA areas only for the remainder. (Kiryl)
>---
> .../ABI/testing/sysfs-kernel-kexec-kdump | 3 ++
> Documentation/admin-guide/kdump/kdump.rst | 22 ++++++--
> .../admin-guide/kernel-parameters.txt | 16 +++++-
> arch/arm64/mm/init.c | 2 +-
> arch/powerpc/include/asm/kexec.h | 2 -
> arch/powerpc/kexec/core.c | 12 ++---
> arch/powerpc/mm/mem.c | 6 +--
> arch/riscv/mm/init.c | 2 +-
> arch/x86/kernel/setup.c | 2 +-
> include/linux/crash_reserve.h | 14 ++++-
> include/linux/hugetlb.h | 12 +++++
> kernel/crash_reserve.c | 51 ++++++++++++++-----
> mm/hugetlb_cma.c | 50 ++++++++++++++++++
> mm/mm_init.c | 2 +
> 14 files changed, 159 insertions(+), 37 deletions(-)
>
>diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
>index f59051b5d96d7..9197cbbcbe7c8 100644
>--- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
>+++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
>@@ -58,4 +58,7 @@ Description: read only
> the Contiguous Memory Allocator (CMA) area that are allocated
> to the crash (kdump) kernel. It lists the start and end physical
> addresses of CMA regions assigned for crashkernel use.
>+ This includes existing HugeTLB CMA memory selected with
>+ crashkernel=size,cma. These ranges remain usable
>+ by the running kernel and are excluded from the vmcore.
> User: kdump service
>diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
>index 7587caadbae1a..91779205d1456 100644
>--- a/Documentation/admin-guide/kdump/kdump.rst
>+++ b/Documentation/admin-guide/kdump/kdump.rst
>@@ -313,9 +313,25 @@ crashkernel syntax
>
> 4) crashkernel=size,cma
>
>- Reserve additional crash kernel memory from CMA. This reservation is
>- usable by the first system's userspace memory and kernel movable
>- allocations (memory balloon, zswap). Pages allocated from this memory
>+ Reserve additional crash kernel memory from CMA. Existing HugeTLB CMA
>+ memory is used first, and dedicated CMA areas are reserved for any
>+ remaining amount. For example, this reuses 2G from the existing 6G pool
>+ without reserving additional CMA memory::
>+
>+ hugetlb_cma=6G crashkernel=256M crashkernel=2G,cma
>+
>+ With a smaller HugeTLB CMA pool, the remainder is reserved separately::
>+
>+ hugetlb_cma=2G crashkernel=256M crashkernel=4G,cma
>+
>+ This reuses the existing 2G and reserves another 2G of dedicated CMA.
>+ Both kinds of area use the same limit of four physical ranges. If there
>+ is insufficient memory or too few range slots, the kernel reports the
>+ shortfall. Normal CMA alignment applies to dedicated reservations.
>+
>+ The selected memory remains usable by the first system's userspace,
>+ including HugeTLB allocations, and kernel movable allocations
>+ (memory balloon, zswap). Pages allocated from this memory
> range will not be included in the vmcore so this should not be used if
> dumping of userspace memory is intended and it has to be expected that
> some movable kernel pages may be missing from the dump.
>diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>index 0b3c140babd94..a1fb40e500097 100644
>--- a/Documentation/admin-guide/kernel-parameters.txt
>+++ b/Documentation/admin-guide/kernel-parameters.txt
>@@ -1100,7 +1100,21 @@ Kernel parameters
> or memory reserved is below 4G.
> crashkernel=size[KMG],cma
> [KNL, X86, ARM64, RISCV, PPC] Reserve additional crash
>- kernel memory from CMA. This reservation is usable by
>+ kernel memory from CMA. Existing hugetlb_cma memory is
>+ used first, and dedicated CMA areas are reserved for any
>+ remaining amount. For example:
>+ hugetlb_cma=6G crashkernel=256M crashkernel=2G,cma
>+ reuses 2G without reserving more CMA, while:
>+ hugetlb_cma=2G crashkernel=256M crashkernel=4G,cma
>+ reuses 2G and reserves another 2G of dedicated CMA.
>+
>+ Both kinds of area use the same limit of four physical
>+ ranges. If the available memory or range slots cannot
>+ cover the requested size, the kernel reports the
>+ shortfall. Normal CMA alignment applies to dedicated
>+ reservations.
>+
>+ The selected memory remains usable by
> the first system's userspace memory and kernel movable
> allocations (memory balloon, zswap). Pages allocated
> from this memory range will not be included in the vmcore
>diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>index 4e7682dfe366c..a781cc60b4282 100644
>--- a/arch/arm64/mm/init.c
>+++ b/arch/arm64/mm/init.c
>@@ -114,7 +114,7 @@ static void __init arch_reserve_crashkernel(void)
> return;
>
> reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
>- reserve_crashkernel_cma(cma_size);
>+ crashkernel_cma_set_size(cma_size);
> }
>
> static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
>diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
>index e02710d6a2e1a..d3b5028102cdd 100644
>--- a/arch/powerpc/include/asm/kexec.h
>+++ b/arch/powerpc/include/asm/kexec.h
>@@ -117,11 +117,9 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt, struct crash_mem
> #ifdef CONFIG_CRASH_RESERVE
> int __init overlaps_crashkernel(unsigned long start, unsigned long size);
> extern void arch_reserve_crashkernel(void);
>-extern void kdump_cma_reserve(void);
> #else
> static inline void arch_reserve_crashkernel(void) {}
> static inline int overlaps_crashkernel(unsigned long start, unsigned long
> size) { return 0; }
>-static inline void kdump_cma_reserve(void) { }
> #endif
>
> #if defined(CONFIG_CRASH_DUMP)
>diff --git a/arch/powerpc/kexec/core.c b/arch/powerpc/kexec/core.c
>index dc44f11be353e..1b70eb10beac2 100644
>--- a/arch/powerpc/kexec/core.c
>+++ b/arch/powerpc/kexec/core.c
>@@ -62,8 +62,6 @@ void machine_kexec(struct kimage *image)
>
> #ifdef CONFIG_CRASH_RESERVE
>
>-static unsigned long long crashk_cma_size;
>-
> static unsigned long long __init get_crash_base(unsigned long long
> crash_base)
> {
>
>@@ -107,6 +105,7 @@ static unsigned long long __init get_crash_base(unsigned long long crash_base)
> void __init arch_reserve_crashkernel(void)
> {
> unsigned long long crash_size, crash_base, crash_end;
>+ unsigned long long cma_size = 0;
> unsigned long long kernel_start, kernel_size;
> unsigned long long total_mem_sz;
> int ret;
>@@ -115,7 +114,7 @@ void __init arch_reserve_crashkernel(void)
>
> /* use common parsing */
> ret = parse_crashkernel(boot_command_line, total_mem_sz, &crash_size,
>- &crash_base, NULL, &crashk_cma_size, NULL);
>+ &crash_base, NULL, &cma_size, NULL);
>
> if (ret)
> return;
>@@ -133,12 +132,7 @@ void __init arch_reserve_crashkernel(void)
> }
>
> reserve_crashkernel_generic(crash_size, crash_base, 0, false);
>-}
>-
>-void __init kdump_cma_reserve(void)
>-{
>- if (crashk_cma_size)
>- reserve_crashkernel_cma(crashk_cma_size);
>+ crashkernel_cma_set_size(cma_size);
> }
>
> int __init overlaps_crashkernel(unsigned long start, unsigned long size)
>diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
>index b617b69452cd6..d6e84dc1e24c5 100644
>--- a/arch/powerpc/mm/mem.c
>+++ b/arch/powerpc/mm/mem.c
>@@ -272,12 +272,10 @@ void __init arch_mm_preinit(void)
> {
>
> /*
>- * Reserve large chunks of memory for use by CMA for kdump, fadump, KVM
>- * and hugetlb. These must be called after pageblock_order is
>- * initialised.
>+ * Reserve large chunks of memory for use by CMA for fadump and KVM.
>+ * These must be called after pageblock_order is initialised.
> */
> fadump_cma_init();
>- kdump_cma_reserve();
> kvm_cma_reserve();
>
> /*
>diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>index e822fce0af4b0..194045dc3fed6 100644
>--- a/arch/riscv/mm/init.c
>+++ b/arch/riscv/mm/init.c
>@@ -1357,7 +1357,7 @@ static void __init arch_reserve_crashkernel(void)
> return;
>
> reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
>- reserve_crashkernel_cma(cma_size);
>+ crashkernel_cma_set_size(cma_size);
> }
>
> void __init paging_init(void)
>diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>index 19fc8e1714e64..8848e207780b5 100644
>--- a/arch/x86/kernel/setup.c
>+++ b/arch/x86/kernel/setup.c
>@@ -627,7 +627,7 @@ static void __init arch_reserve_crashkernel(void)
> }
>
> reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
>- reserve_crashkernel_cma(cma_size);
>+ crashkernel_cma_set_size(cma_size);
> }
>
> static struct resource standard_io_resources[] = {
>diff --git a/include/linux/crash_reserve.h b/include/linux/crash_reserve.h
>index 30864d90d7f50..b11d7814979cc 100644
>--- a/include/linux/crash_reserve.h
>+++ b/include/linux/crash_reserve.h
>@@ -5,6 +5,7 @@
> #include <linux/linkage.h>
> #include <linux/elfcore.h>
> #include <linux/elf.h>
>+#include <linux/range.h>
> #ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
> #include <asm/crash_reserve.h>
> #endif
>@@ -31,7 +32,18 @@ int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
> unsigned long long *low_size, unsigned long long *cma_size,
> bool *high);
>
>-void __init reserve_crashkernel_cma(unsigned long long cma_size);
>+#if defined(CONFIG_CRASH_RESERVE) && defined(CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION)
>+void __init crashkernel_cma_set_size(unsigned long long size);
>+void __init reserve_crashkernel_cma(void);
>+#else
>+static inline void __init crashkernel_cma_set_size(unsigned long long size)
>+{
>+}
>+
>+static inline void __init reserve_crashkernel_cma(void)
>+{
>+}
>+#endif
>
> #ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
> #ifndef arch_add_crash_res_to_iomem
>diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>index 58f755e70e966..69732e4cc03e2 100644
>--- a/include/linux/hugetlb.h
>+++ b/include/linux/hugetlb.h
>@@ -1349,12 +1349,24 @@ static inline spinlock_t *huge_pte_lock(struct hstate *h,
> return ptl;
> }
>
>+struct range;
>+
> #if defined(CONFIG_HUGETLB_PAGE) && defined(CONFIG_CMA)
> extern void __init hugetlb_cma_reserve(void);
>+unsigned long long __init
>+hugetlb_cma_add_crashkernel_ranges(unsigned long long size, struct range *ranges,
>+ int *nr_ranges, int max_ranges);
> #else
> static inline __init void hugetlb_cma_reserve(void)
> {
> }
>+
>+static inline unsigned long long
>+hugetlb_cma_add_crashkernel_ranges(unsigned long long size, struct range *ranges,
>+ int *nr_ranges, int max_ranges)
>+{
>+ return 0;
>+}
> #endif
>
> #ifdef CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING
>diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
>index eee37a11380ce..53d76ba6b3c31 100644
>--- a/kernel/crash_reserve.c
>+++ b/kernel/crash_reserve.c
>@@ -16,6 +16,7 @@
> #include <linux/kmemleak.h>
> #include <linux/cma.h>
> #include <linux/crash_reserve.h>
>+#include <linux/hugetlb.h>
>
> #include <asm/page.h>
> #include <asm/sections.h>
>@@ -340,9 +341,9 @@ int __init parse_crashkernel(char *cmdline,
> * optional CMA reservation
> * cma_base is ignored
> */
>- if (cma_size)
>- __parse_crashkernel(cmdline, 0, cma_size,
>- &cma_base, suffix_tbl[SUFFIX_CMA]);
>+ if (cma_size && __parse_crashkernel(cmdline, 0, cma_size,
>+ &cma_base, suffix_tbl[SUFFIX_CMA]))
>+ *cma_size = 0;
> #endif
> if (!*crash_size)
> ret = -EINVAL;
>@@ -470,21 +471,41 @@ void __init reserve_crashkernel_generic(unsigned long long crash_size,
> }
>
> struct range crashk_cma_ranges[CRASHKERNEL_CMA_RANGES_MAX];
>+static unsigned long long crashkernel_cma_size __initdata;
>+
>+void __init crashkernel_cma_set_size(unsigned long long cma_size)
>+{
>+ crashkernel_cma_size = cma_size;
>+}
>+
> #ifdef CRASHKERNEL_CMA
> int crashk_cma_cnt;
>-void __init reserve_crashkernel_cma(unsigned long long cma_size)
>+void __init reserve_crashkernel_cma(void)
> {
>- unsigned long long request_size = roundup(cma_size, PAGE_SIZE);
>- unsigned long long reserved_size = 0;
>+ unsigned long long cma_size = crashkernel_cma_size;
>+ unsigned long long request_size, reserved_size, reused_size;
>
>- if (!cma_size)
>+ if (!cma_size || crashk_res.start >= crashk_res.end)
> return;
>
>+ if (cma_size > ULLONG_MAX - (PAGE_SIZE - 1)) {
>+ pr_warn("crashkernel CMA size is too large\n");
>+ return;
>+ }
>+ cma_size = roundup(cma_size, PAGE_SIZE);
>+ reused_size = hugetlb_cma_add_crashkernel_ranges(cma_size,
>+ crashk_cma_ranges,
>+ &crashk_cma_cnt,
>+ CRASHKERNEL_CMA_RANGES_MAX);
>+ reserved_size = reused_size;
>+ request_size = cma_size - reused_size;
>+
> while (cma_size > reserved_size &&
> crashk_cma_cnt < CRASHKERNEL_CMA_RANGES_MAX) {
>
> struct cma *res;
>
>+ request_size = min(request_size, cma_size - reserved_size);
> if (cma_declare_contiguous(0, request_size, 0, 0, 0, false,
> "crashkernel", &res)) {
> /* reservation failed, try half-sized blocks */
>@@ -500,21 +521,23 @@ void __init reserve_crashkernel_cma(unsigned long long cma_size)
> crashk_cma_ranges[crashk_cma_cnt].start +
> cma_get_size(res) - 1;
> ++crashk_cma_cnt;
>- reserved_size += request_size;
>+ reserved_size += cma_get_size(res);
> }
>
> if (cma_size > reserved_size)
>- pr_warn("crashkernel CMA reservation failed: %lld MB requested, %lld MB reserved in %d ranges\n",
>- cma_size >> 20, reserved_size >> 20, crashk_cma_cnt);
>+ pr_warn("crashkernel CMA reservation failed: %llu MB requested, %llu MB reused, %llu MB newly reserved in %d ranges\n",
>+ cma_size >> 20, reused_size >> 20,
>+ (reserved_size - reused_size) >> 20, crashk_cma_cnt);
> else
>- pr_info("crashkernel CMA reserved: %lld MB in %d ranges\n",
>- reserved_size >> 20, crashk_cma_cnt);
>+ pr_info("crashkernel CMA: %llu MB reused, %llu MB newly reserved in %d ranges\n",
>+ reused_size >> 20, (reserved_size - reused_size) >> 20,
>+ crashk_cma_cnt);
> }
>
> #else /* CRASHKERNEL_CMA */
>-void __init reserve_crashkernel_cma(unsigned long long cma_size)
>+void __init reserve_crashkernel_cma(void)
> {
>- if (cma_size)
>+ if (crashkernel_cma_size)
> pr_warn("crashkernel CMA reservation not supported\n");
> }
> #endif
>diff --git a/mm/hugetlb_cma.c b/mm/hugetlb_cma.c
>index cd6a64986278a..cd6f64da31a2c 100644
>--- a/mm/hugetlb_cma.c
>+++ b/mm/hugetlb_cma.c
>@@ -11,6 +11,8 @@
> #include <linux/memblock.h>
> #include <linux/math.h>
> #include <linux/math64.h>
>+#include <linux/range.h>
>+#include "cma.h"
> #include "internal.h"
> #include "hugetlb_cma.h"
>
>@@ -387,6 +389,54 @@ void __init hugetlb_cma_reserve(void)
> hugetlb_cma_size = 0;
> }
>
>+/**
>+ * hugetlb_cma_add_crashkernel_ranges - share HugeTLB CMA with the crash kernel
>+ * @size: maximum number of bytes to share, aligned to PAGE_SIZE
>+ * @ranges: crash kernel memory ranges
>+ * @nr_ranges: number of entries already in @ranges, updated on return
>+ * @max_ranges: capacity of @ranges
>+ *
>+ * The shared memory remains available to the HugeTLB allocator until a crash.
>+ * Only physical ranges belonging to successfully reserved CMA areas are added.
>+ *
>+ * Return: number of bytes shared.
>+ */
>+unsigned long long __init
>+hugetlb_cma_add_crashkernel_ranges(unsigned long long size, struct range *ranges,
>+ int *nr_ranges, int max_ranges)
>+{
>+ unsigned long long shared_size = 0;
>+ int nid, i;
>+
>+ for_each_node_mask(nid, hugetlb_bootmem_nodes) {
>+ struct cma *cma = hugetlb_cma[nid];
>+
>+ if (!cma)
>+ continue;
>+
>+ for (i = 0; i < cma->nranges; i++) {
>+ struct cma_memrange *cmr = &cma->ranges[i];
>+ unsigned long long range_size;
>+ struct range *range;
>+
>+ if (shared_size == size || *nr_ranges == max_ranges)
>+ return shared_size;
>+
>+ range_size = min_t(unsigned long long,
>+ PFN_PHYS(cmr->count), size - shared_size);
>+ range = &ranges[(*nr_ranges)++];
>+ range->start = PFN_PHYS(cmr->base_pfn);
>+ range->end = range->start + range_size - 1;
>+ shared_size += range_size;
>+
>+ /* Keep shared pages reserved if CMA activation fails. */
>+ cma_reserve_pages_on_error(cma);
>+ }
>+ }
>+
>+ return shared_size;
>+}
>+
> bool hugetlb_cma_exclusive_alloc(void)
> {
> return hugetlb_cma_only;
>diff --git a/mm/mm_init.c b/mm/mm_init.c
>index a9d848c92678b..2367af05570bd 100644
>--- a/mm/mm_init.c
>+++ b/mm/mm_init.c
>@@ -28,6 +28,7 @@
> #include <linux/swap.h>
> #include <linux/cma.h>
> #include <linux/crash_dump.h>
>+#include <linux/crash_reserve.h>
> #include <linux/execmem.h>
> #include <linux/sizes.h>
> #include <linux/vmstat.h>
>@@ -2686,6 +2687,7 @@ void __init mm_core_init_early(void)
> free_area_init();
>
> hugetlb_cma_reserve();
>+ reserve_crashkernel_cma();
> hugetlb_bootmem_alloc();
>
> sparse_init();
>
--- Thanks!
^ permalink raw reply [flat|nested] 5+ messages in thread