x86/mm: add a function to check if a pfn is UC/UC-/WC

Web:        https://git.kernel.org/torvalds/c/b8d7044bcff7a955257b242515bcf1e5045edd9b
Commit:     b8d7044bcff7a955257b242515bcf1e5045edd9b
Parent:     05992edc279237d5803d64578e0c72b604970a49
Refname:    refs/heads/master
Author:     Haozhong Zhang <[email protected]>
AuthorDate: Wed Dec 20 15:29:28 2017 +0800
Committer:  Radim Krčmář <[email protected]>
CommitDate: Tue Jan 16 16:40:09 2018 +0100

    x86/mm: add a function to check if a pfn is UC/UC-/WC
    
    Check whether the PAT memory type of a pfn cannot be overridden by
    MTRR UC memory type, i.e. the PAT memory type is UC, UC- or WC. This
    function will be used by KVM to distinguish MMIO pfns and give them
    UC memory type in the EPT page tables (on Intel processors, EPT
    memory types work like MTRRs).
    
    Signed-off-by: Haozhong Zhang <[email protected]>
    Reviewed-by: Xiao Guangrong <[email protected]>
    Signed-off-by: Paolo Bonzini <[email protected]>
    Signed-off-by: Radim Krčmář <[email protected]>
---
 arch/x86/include/asm/pat.h |  2 ++
 arch/x86/mm/pat.c          | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index 8a3ee355b422..92015c65fa2a 100644
--- a/arch/x86/include/asm/pat.h
+++ b/arch/x86/include/asm/pat.h
@@ -22,4 +22,6 @@ 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_immune_to_uc_mtrr(unsigned long pfn);
+
 #endif /* _ASM_X86_PAT_H */
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index fe7d57a8fb60..1555bd7d3449 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -677,6 +677,25 @@ static enum page_cache_mode lookup_memtype(u64 paddr)
 	return rettype;
 }
 
+/**
+ * pat_pfn_immune_to_uc_mtrr - Check whether the PAT memory type
+ * of @pfn cannot be overridden by UC MTRR memory type.
+ *
+ * Only to be called when PAT is enabled.
+ *
+ * Returns true, if the PAT memory type of @pfn is UC, UC-, or WC.
+ * Returns false in other cases.
+ */
+bool pat_pfn_immune_to_uc_mtrr(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 ||
+	       cm == _PAGE_CACHE_MODE_WC;
+}
+EXPORT_SYMBOL_GPL(pat_pfn_immune_to_uc_mtrr);
+
 /**
  * io_reserve_memtype - Request a memory type mapping for a region of memory
  * @start: start (physical address) of the region
--
To unsubscribe from this list: send the line "unsubscribe git-commits-head" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html