Messages in this thread | | | Subject | Re: [PATCH v3 12/12] mm/debug_vm_pgtable: Fix corrupted page flag | From | Gavin Shan <> | Date | Thu, 22 Jul 2021 16:54:29 +1000 |
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Hi Anshuman,
On 7/22/21 1:51 PM, Anshuman Khandual wrote: > Small nit: > > s/Fix corrupted page flag/Fix page flag corruption on arm64/ >
Sure, The replacement will be applied in v4, thanks!
> On 7/21/21 5:33 PM, Gavin Shan wrote: >> Hi Anshuman, >> >> On 7/21/21 8:18 PM, Anshuman Khandual wrote: >>> On 7/19/21 6:36 PM, Gavin Shan wrote: >>>> In page table entry modifying tests, set_xxx_at() are used to populate >>>> the page table entries. On ARM64, PG_arch_1 is set to the target page >>>> flag if execution permission is given. The page flag is kept when the >>>> page is free'd to buddy's free area list. However, it will trigger page >>>> checking failure when it's pulled from the buddy's free area list, as >>>> the following warning messages indicate. >>>> >>>> BUG: Bad page state in process memhog pfn:08000 >>>> page:0000000015c0a628 refcount:0 mapcount:0 \ >>>> mapping:0000000000000000 index:0x1 pfn:0x8000 >>>> flags: 0x7ffff8000000800(arch_1|node=0|zone=0|lastcpupid=0xfffff) >>>> raw: 07ffff8000000800 dead000000000100 dead000000000122 0000000000000000 >>>> raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000 >>>> page dumped because: PAGE_FLAGS_CHECK_AT_PREP flag(s) set >>>> >>>> This fixes the issue by clearing PG_arch_1 through flush_dcache_page() >>>> after set_xxx_at() is called. >>> >>> Could you please add comments before each flush_dcache_page() instance >>> explaining why this is needed for arm64 platforms with relevant PG_arch_1 >>> context and how this does not have any adverse effect on other platforms ? >>> It should be easy for some one looking at this code after a while to figure >>> out from where flush_dcache_page() came from. >>> >> >> Good point. I will improve chage log to include the commit ID in v4 where the >> page flag (PG_arch_1) is used and explain how. In that case, it's much clearer >> to understand the reason why we need flush_dcache_page() after set_xxx_at() on >> ARM64. > > But also some in code comments where flush_dcache_page() is being called. >
Yes, I will add some comments where flush_dcache_page() is called in v4.
Thanks, Gavin
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