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.
