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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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6d332747fa
In a system with DBM (dirty bit management) capable agents there is a
possible race between a CPU executing ptep_set_access_flags() (maybe
non-DBM capable) and a hardware update of the dirty state (clearing of
PTE_RDONLY). The scenario:
a) the pte is writable (PTE_WRITE set), clean (PTE_RDONLY set) and old
(PTE_AF clear)
b) ptep_set_access_flags() is called as a result of a read access and it
needs to set the pte to writable, clean and young (PTE_AF set)
c) a DBM-capable agent, as a result of a different write access, is
marking the entry as young (setting PTE_AF) and dirty (clearing
PTE_RDONLY)
The current ptep_set_access_flags() implementation would set the
PTE_RDONLY bit in the resulting value overriding the DBM update and
losing the dirty state.
This patch fixes such race by setting PTE_RDONLY to the most permissive
(lowest value) of the current entry and the new one.
Fixes:
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|---|---|---|
| .. | ||
| cache.S | ||
| context.c | ||
| copypage.c | ||
| dma-mapping.c | ||
| dump.c | ||
| extable.c | ||
| fault.c | ||
| flush.c | ||
| hugetlbpage.c | ||
| init.c | ||
| ioremap.c | ||
| kasan_init.c | ||
| Makefile | ||
| mmap.c | ||
| mmu.c | ||
| numa.c | ||
| pageattr.c | ||
| pgd.c | ||
| physaddr.c | ||
| proc.S | ||
| ptdump_debugfs.c | ||