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
From 1584195858245701208@xxx Thu Nov 16 04:35:02 +0000 2017
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