From: Tarun Sahu <tarunsahu@google.com>
To: Pasha Tatashin <pasha.tatashin@soleen.com>,
Mike Rapoport <rppt@kernel.org>,
robin.murphy@arm.com, maz@kernel.org, will@kernel.org,
David Matlack <dmatlack@google.com>,
Alexander Graf <graf@amazon.com>,
seanjc@google.com, jgg@nvidia.com, loganodell@google.com,
arnd@arndb.de, dwmw2@infradead.org, baolu.lu@linux.intel.com,
Bjorn Helgaas <bhelgaas@google.com>,
oupton@kernel.org, alex@shazbot.org, gle.com@google.com,
pbonzini@redhat.com, Andrew Morton <akpm@linux-foundation.org>,
kevin.tian@intel.com, joro@8bytes.org
Cc: kvmarm@lists.linux.dev, linux-pci@vger.kernel.org,
Pratyush Yadav <pratyush@kernel.org>,
kexec@lists.infradead.org, kvm@vger.kernel.org,
iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
skhawaja@google.com, sagis@google.com,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Tarun Sahu <tarunsahu@google.com>
Subject: [PATCH v4 18/19] mm: memfd_luo: Add feature header to struct memfd_luo_folio_ser
Date: Tue, 10 Nov 2026 05:02:01 +0000 [thread overview]
Message-ID: <20261110050202.529473-19-tarunsahu@google.com> (raw)
In-Reply-To: <20261110050202.529473-1-tarunsahu@google.com>
Precede each serialized folio entry in the preserved memfd folio array
with struct kho_ser_hdr via DECLARE_KHO_SER so future per-folio memfd
features can append fields to struct memfd_luo_folio_ser without breaking
compatibility between adjacent kernels.
Allocate the preserved folio array using kho_ser_size(memfd_luo_folio_ser)
per entry and initialize each entry feature header in
memfd_luo_preserve_folios(). On the incoming path in
memfd_luo_discard_folios() and memfd_luo_retrieve_folios(), validate each
entry feature header with kho_ser_validate() and advance between entries
using fhdr->size so entries written with a different feature layout are
traversed accurately.
Signed-off-by: Tarun Sahu <tarunsahu@google.com>
---
include/linux/kho/abi/memfd.h | 6 ++--
mm/memfd_luo.c | 66 +++++++++++++++++++++++++----------
2 files changed, 51 insertions(+), 21 deletions(-)
diff --git a/include/linux/kho/abi/memfd.h b/include/linux/kho/abi/memfd.h
index 27f8880ee593..1aad47ce7322 100644
--- a/include/linux/kho/abi/memfd.h
+++ b/include/linux/kho/abi/memfd.h
@@ -51,6 +51,8 @@
* @pfn: The page frame number of the folio.
* @flags: Flags to describe the state of the folio.
* @index: The page offset (pgoff_t) of the folio within the original file.
+ *
+ * Preceded by &struct kho_ser_hdr.
*/
struct memfd_luo_folio_ser {
u64 pfn:52;
@@ -58,9 +60,7 @@ struct memfd_luo_folio_ser {
u64 index;
};
-static_assert(sizeof(struct memfd_luo_folio_ser) == 16);
-static_assert(!IS_ENABLED(CONFIG_64BIT) ||
- __alignof__(struct memfd_luo_folio_ser) == 8);
+DECLARE_KHO_SER(memfd_luo_folio_ser, 16, 0, 0);
/*
* The set of seals this version supports preserving. If support for any new
diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index 94510f73a606..c00daa8a508e 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -86,10 +86,10 @@
static int memfd_luo_preserve_folios(struct file *file,
struct memfd_luo_ser *ser,
- struct memfd_luo_folio_ser **out_folios_ser)
+ DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, **out_folios_ser))
{
struct inode *inode = file_inode(file);
- struct memfd_luo_folio_ser *folios_ser;
+ DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *folios_ser);
unsigned int max_folios;
long i, size, nr_pinned;
struct folio **folios;
@@ -138,14 +138,16 @@ static int memfd_luo_preserve_folios(struct file *file,
}
nr_folios = nr_pinned;
- folios_ser = vcalloc(nr_folios, sizeof(*folios_ser));
+ folios_ser = vcalloc(nr_folios, kho_ser_size(memfd_luo_folio_ser));
if (!folios_ser) {
err = -ENOMEM;
goto err_unpin;
}
for (i = 0; i < nr_folios; i++) {
- struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+ DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *fhdr) =
+ (void *)folios_ser + i * kho_ser_size(memfd_luo_folio_ser);
+ struct memfd_luo_folio_ser *pfolio;
struct folio *folio = folios[i];
err = kho_preserve_folio(folio);
@@ -195,6 +197,8 @@ static int memfd_luo_preserve_folios(struct file *file,
folio_unlock(folio);
+ kho_ser_init(fhdr, memfd_luo_folio_ser);
+ pfolio = kho_ser_payload(fhdr, memfd_luo_folio_ser);
pfolio->pfn = folio_pfn(folio);
pfolio->flags = MEMFD_LUO_FOLIO_DIRTY | MEMFD_LUO_FOLIO_UPTODATE;
pfolio->index = folio->index;
@@ -228,7 +232,7 @@ static int memfd_luo_preserve_folios(struct file *file,
}
static void memfd_luo_unpreserve_folios(DECLARE_KHO_SER_HDR(kho_vmalloc, *folios_fhdr),
- struct memfd_luo_folio_ser *folios_ser,
+ const DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *folios_ser),
u64 nr_folios)
{
long i;
@@ -239,7 +243,10 @@ static void memfd_luo_unpreserve_folios(DECLARE_KHO_SER_HDR(kho_vmalloc, *folios
kho_unpreserve_vmalloc(folios_fhdr);
for (i = 0; i < nr_folios; i++) {
- const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+ const DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *fhdr) =
+ (const void *)folios_ser + i * kho_ser_size(memfd_luo_folio_ser);
+ const struct memfd_luo_folio_ser *pfolio =
+ kho_ser_payload(fhdr, memfd_luo_folio_ser);
struct folio *folio;
if (!pfolio->pfn)
@@ -277,7 +284,7 @@ memfd_luo_ser_init(DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr))
static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
{
struct inode *inode = file_inode(args->file);
- struct memfd_luo_folio_ser *folios_ser;
+ DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *folios_ser);
DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
int err = 0, seals;
@@ -384,16 +391,23 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
inode_unlock(inode);
}
-static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_ser,
+static void memfd_luo_discard_folios(const DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *folios_ser),
u64 nr_folios)
{
+ const DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *fhdr) = folios_ser;
u64 i;
- for (i = 0; i < nr_folios; i++) {
- const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+ for (i = 0; i < nr_folios; i++, fhdr = (const void *)fhdr + fhdr->size) {
+ const struct memfd_luo_folio_ser *pfolio;
struct folio *folio;
phys_addr_t phys;
+ if (kho_ser_validate(fhdr, memfd_luo_folio_ser)) {
+ pr_warn("invalid folio feature header, folios not discarded\n");
+ return;
+ }
+
+ pfolio = kho_ser_payload(fhdr, memfd_luo_folio_ser);
if (!pfolio->pfn)
continue;
@@ -411,7 +425,7 @@ static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_se
static void memfd_luo_finish(struct liveupdate_file_op_args *args)
{
- struct memfd_luo_folio_ser *folios_ser;
+ DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *folios_ser);
DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
@@ -447,9 +461,10 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args)
}
static int memfd_luo_retrieve_folios(struct file *file,
- struct memfd_luo_folio_ser *folios_ser,
+ const DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *folios_ser),
u64 nr_folios)
{
+ const DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *fhdr) = folios_ser;
struct inode *inode = file_inode(file);
struct address_space *mapping = inode->i_mapping;
struct folio *folio;
@@ -457,12 +472,20 @@ static int memfd_luo_retrieve_folios(struct file *file,
int err = -EIO;
long i;
- for (i = 0; i < nr_folios; i++) {
- const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+ for (i = 0; i < nr_folios; i++, fhdr = (const void *)fhdr + fhdr->size) {
+ const struct memfd_luo_folio_ser *pfolio;
phys_addr_t phys;
u64 index;
int flags;
+ err = kho_ser_validate(fhdr, memfd_luo_folio_ser);
+ if (err) {
+ pr_err("memfd_luo_folio_ser feature validation failed: %pe\n",
+ ERR_PTR(err));
+ goto put_folios;
+ }
+
+ pfolio = kho_ser_payload(fhdr, memfd_luo_folio_ser);
if (!pfolio->pfn)
continue;
@@ -472,7 +495,7 @@ static int memfd_luo_retrieve_folios(struct file *file,
pr_err("Unable to restore folio at physical address: %llx\n",
phys);
err = -EIO;
- goto put_folios;
+ goto next_put_folios;
}
index = pfolio->index;
flags = pfolio->flags;
@@ -524,15 +547,22 @@ static int memfd_luo_retrieve_folios(struct file *file,
unlock_folio:
folio_unlock(folio);
folio_put(folio);
+next_put_folios:
+ i++;
+ fhdr = (const void *)fhdr + fhdr->size;
put_folios:
/*
* Note: don't free the folios already added to the file. They will be
* freed when the file is freed. Free the ones not added yet here.
*/
- for (long j = i + 1; j < nr_folios; j++) {
- const struct memfd_luo_folio_ser *pfolio = &folios_ser[j];
+ for (; i < nr_folios; i++, fhdr = (const void *)fhdr + fhdr->size) {
+ const struct memfd_luo_folio_ser *pfolio;
phys_addr_t phys;
+ if (kho_ser_validate(fhdr, memfd_luo_folio_ser))
+ break;
+
+ pfolio = kho_ser_payload(fhdr, memfd_luo_folio_ser);
if (!pfolio->pfn)
continue;
@@ -549,7 +579,7 @@ static int memfd_luo_retrieve_folios(struct file *file,
static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)
{
- struct memfd_luo_folio_ser *folios_ser;
+ DECLARE_KHO_SER_HDR(memfd_luo_folio_ser, *folios_ser);
DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
struct file *file;
--
2.56.0.506.g506a7eabc5-goog
next prev parent reply other threads:[~2026-11-10 5:02 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-10 5:01 [PATCH v4 00/19] kho, liveupdate: Add feature header for fine-grained ABI compatibility Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 01/19] liveupdate, kho: Remove __packed from KHO, LUO and memfd ABI structures Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 02/19] kho: block: Record the entry size in the block header Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 03/19] kho, memfd_luo: Reference struct kho_vmalloc via serialized pointer Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 04/19] liveupdate: Reference struct luo_file_set_ser " Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 05/19] kho: Add feature header for fine-grained ABI compatibility Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 06/19] kho: kexec_metadata: Add the feature header Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 07/19] kho: vmalloc: " Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 08/19] kho: block: Add the feature header to blocks Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 09/19] liveupdate: Add feature header to struct luo_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 10/19] liveupdate: Add feature header to struct luo_session_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 11/19] liveupdate: Add feature header to struct luo_file_set_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 12/19] liveupdate: Add feature header to struct luo_file_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 13/19] liveupdate: Add feature header to struct luo_flb_header_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 14/19] liveupdate: Add feature header to struct luo_flb_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 15/19] PCI: liveupdate: Add feature header to struct pci_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 16/19] PCI: liveupdate: Add feature header to struct pci_dev_ser Tarun Sahu
2026-11-10 5:02 ` [PATCH v4 17/19] mm: memfd_luo: Add feature header to struct memfd_luo_ser Tarun Sahu
2026-11-10 5:02 ` Tarun Sahu [this message]
2026-11-10 5:02 ` [PATCH v4 19/19] kho: Add KUnit test for the feature header helpers Tarun Sahu
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