Re: [PATCH] arm: flush: check if the folio is reserved for IMO addresses

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2024/2/22 22:38, Russell King (Oracle) wrote:
> On Thu, Feb 22, 2024 at 10:06:04PM +0800, Kefeng Wang wrote:
>>
>>
>> On 2024/2/22 22:01, Yongqiang Liu wrote:
>>> Since commit a4d5613c4dc6 ("arm: extend pfn_valid to take into account
>>> freed memory map alignment") changes the semantics of pfn_valid() to check
>>> presence of the memory map for a PFN. A valid page for an address which
>>> is reserved but not mapped by the kernel[1].In Some uio case we will get
>>> a crash on a system with the following memory layout:
>>>
>>>    node   0: [mem 0x00000000c0a00000-0x00000000cc8fffff]
>>>    node   0: [mem 0x00000000d0000000-0x00000000da1fffff]
>>>    the uio layout is：0xc0900000, 0x100000
>>>
>>> the crash backtrace like:
>>>
>>>     Unable to handle kernel paging request at virtual address bff00000
>>>     [...]
>>>     CPU: 1 PID: 465 Comm: startapp.bin Tainted: G           O      5.10.0 #1
>>>     Hardware name: Generic DT based system
>>>     PC is at b15_flush_kern_dcache_area+0x24/0x3c
>>>     LR is at __sync_icache_dcache+0x6c/0x98
>>>     [...]
>>>      (b15_flush_kern_dcache_area) from (__sync_icache_dcache+0x6c/0x98)
>>>      (__sync_icache_dcache) from (set_pte_at+0x28/0x54)
>>>      (set_pte_at) from (remap_pfn_range+0x1a0/0x274)
>>>      (remap_pfn_range) from (uio_mmap+0x184/0x1b8 [uio])
>>>      (uio_mmap [uio]) from (__mmap_region+0x264/0x5f4)
>>>      (__mmap_region) from (__do_mmap_mm+0x3ec/0x440)
>>>      (__do_mmap_mm) from (do_mmap+0x50/0x58)
>>>      (do_mmap) from (vm_mmap_pgoff+0xfc/0x188)
>>>      (vm_mmap_pgoff) from (ksys_mmap_pgoff+0xac/0xc4)
>>>      (ksys_mmap_pgoff) from (ret_fast_syscall+0x0/0x5c)
>>>     Code: e0801001 e2423001 e1c00003 f57ff04f (ee070f3e)
>>>     ---[ end trace 09cf0734c3805d52 ]---
>>>     Kernel panic - not syncing: Fatal exception
>>>
>>> So check if PG_reserved was set to solve this issue.
>>>
>>> [1]: https://lore.kernel.org/lkml/Zbtdue57RO0QScJM@linux.ibm.com/
>>>
>>> Fixes: a4d5613c4dc6 ("arm: extend pfn_valid to take into account freed memory map alignment")
>>> Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
>>> Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
>>> ---
>>>    arch/arm/mm/flush.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
>>> index d19d140a10c7..f2b99223a0ab 100644
>>> --- a/arch/arm/mm/flush.c
>>> +++ b/arch/arm/mm/flush.c
>>> @@ -15,6 +15,7 @@
>>>    #include <asm/smp_plat.h>
>>>    #include <asm/tlbflush.h>
>>>    #include <linux/hugetlb.h>
>>> +#include <linux/memblock.h>
>> 这个删掉吧然后发出去
> 
> Speak English so that everyone knows what you are saying. You are
> participating in an international community where English is the
> language that we use to communicate between ourselves.
> 
Sorry, I mistake for a internal mail

To Yongqiang, please drop the unnecessary include and as Matthew said,
please consider to use folio helper.

> Thanks.
>