Small nit: s/Fix corrupted page flag/Fix page flag corruption on arm64/ 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.
