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SubjectRe: [PATCH] arm: flush: don't abuse pfn_valid() to check if pfn is in RAM
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On 1/31/2024 4:59 AM, 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. __sync_icache_dcache() should use
> memblock_is_map_memory() instead of pfn_valid() to check if a PFN is in
> RAM or not.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

Humm, what Broadcom platform using a Brahma-B15 CPU are you using out of
curiosity?

> 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
>
> Fixes: a4d5613c4dc6 ("arm: extend pfn_valid to take into account freed memory map alignment")
> Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
> ---
> arch/arm/mm/flush.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
> index d19d140a10c7..11ec6c5ff5fc 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>
>
> #include "mm.h"
>
> @@ -292,7 +293,7 @@ void __sync_icache_dcache(pte_t pteval)
> /* only flush non-aliasing VIPT caches for exec mappings */
> return;
> pfn = pte_pfn(pteval);
> - if (!pfn_valid(pfn))
> + if (!memblock_is_map_memory(PFN_PHYS(pfn)))
> return;
>
> folio = page_folio(pfn_to_page(pfn));

--
Florian
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