It will be used by KVM to check whether a pfn should be mapped to guest as UC.
Signed-off-by: Haozhong Zhang <[email protected]> --- arch/x86/include/asm/pat.h | 2 ++ arch/x86/mm/pat.c | 16 ++++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h index fffb2794dd89..fabb0cf00e77 100644 --- a/arch/x86/include/asm/pat.h +++ b/arch/x86/include/asm/pat.h @@ -21,4 +21,6 @@ int io_reserve_memtype(resource_size_t start, resource_size_t end, void io_free_memtype(resource_size_t start, resource_size_t end); +bool pat_pfn_is_uc_or_uc_minus(unsigned long pfn); + #endif /* _ASM_X86_PAT_H */ diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index fe7d57a8fb60..e1282dd4eeb8 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -677,6 +677,22 @@ static enum page_cache_mode lookup_memtype(u64 paddr) return rettype; } +/** + * Check with PAT whether the memory type of a pfn is UC or UC-. + * + * Only to be called when PAT is enabled. + * + * Returns true, if the memory type of @pfn is UC or UC-. + * Otherwise, returns false. + */ +bool pat_pfn_is_uc_or_uc_minus(unsigned long pfn) +{ + enum page_cache_mode cm = lookup_memtype(PFN_PHYS(pfn)); + + return cm == _PAGE_CACHE_MODE_UC || cm == _PAGE_CACHE_MODE_UC_MINUS; +} +EXPORT_SYMBOL_GPL(pat_pfn_is_uc_or_uc_minus); + /** * io_reserve_memtype - Request a memory type mapping for a region of memory * @start: start (physical address) of the region -- 2.14.1
