x86/mm/mtrr: Enhance MTRR checks in kernel mapping helpers
This patch adds the argument 'uniform' to mtrr_type_lookup(),
which gets set to 1 when a given range is covered uniformly by
MTRRs, i.e. the range is fully covered by a single MTRR entry or
the default type.
Change pud_set_huge() and pmd_set_huge() to honor the 'uniform'
flag to see if it is safe to create a huge page mapping in the
range.
This allows them to create a huge page mapping in a range
covered by a single MTRR entry of any memory type. It also
detects a non-optimal request properly. They continue to check
with the WB type since it does not effectively change the
uniform mapping even if a request spans multiple MTRR entries.
pmd_set_huge() logs a warning message to a non-optimal request
so that driver writers will be aware of such a case. Drivers
should make a mapping request aligned to a single MTRR entry
when the range is covered by MTRRs.
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
[ Realign, flesh out comments, improve warning message. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Elliott@hp.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave.hansen@intel.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: pebolle@tiscali.nl
Link: http://lkml.kernel.org/r/1431714237-880-7-git-send-email-toshi.kani@hp.com
Link: http://lkml.kernel.org/r/1432628901-18044-8-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 35af677..372ad42 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -267,9 +267,9 @@
* request is for WB.
*/
if (req_type == _PAGE_CACHE_MODE_WB) {
- u8 mtrr_type;
+ u8 mtrr_type, uniform;
- mtrr_type = mtrr_type_lookup(start, end);
+ mtrr_type = mtrr_type_lookup(start, end, &uniform);
if (mtrr_type != MTRR_TYPE_WRBACK)
return _PAGE_CACHE_MODE_UC_MINUS;
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index c30f981..fb0a9dd 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -566,19 +566,28 @@
/**
* pud_set_huge - setup kernel PUD mapping
*
- * MTRR can override PAT memory types with 4KiB granularity. Therefore,
- * this function does not set up a huge page when the range is covered
- * by a non-WB type of MTRR. MTRR_TYPE_INVALID indicates that MTRR are
- * disabled.
+ * MTRRs can override PAT memory types with 4KiB granularity. Therefore, this
+ * function sets up a huge page only if any of the following conditions are met:
+ *
+ * - MTRRs are disabled, or
+ *
+ * - MTRRs are enabled and the range is completely covered by a single MTRR, or
+ *
+ * - MTRRs are enabled and the corresponding MTRR memory type is WB, which
+ * has no effect on the requested PAT memory type.
+ *
+ * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger
+ * page mapping attempt fails.
*
* Returns 1 on success and 0 on failure.
*/
int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
{
- u8 mtrr;
+ u8 mtrr, uniform;
- mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE);
- if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != MTRR_TYPE_INVALID))
+ mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE, &uniform);
+ if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
+ (mtrr != MTRR_TYPE_WRBACK))
return 0;
prot = pgprot_4k_2_large(prot);
@@ -593,20 +602,21 @@
/**
* pmd_set_huge - setup kernel PMD mapping
*
- * MTRR can override PAT memory types with 4KiB granularity. Therefore,
- * this function does not set up a huge page when the range is covered
- * by a non-WB type of MTRR. MTRR_TYPE_INVALID indicates that MTRR are
- * disabled.
+ * See text over pud_set_huge() above.
*
* Returns 1 on success and 0 on failure.
*/
int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
{
- u8 mtrr;
+ u8 mtrr, uniform;
- mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE);
- if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != MTRR_TYPE_INVALID))
+ mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE, &uniform);
+ if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
+ (mtrr != MTRR_TYPE_WRBACK)) {
+ pr_warn_once("%s: Cannot satisfy [mem %#010llx-%#010llx] with a huge-page mapping due to MTRR override.\n",
+ __func__, addr, addr + PMD_SIZE);
return 0;
+ }
prot = pgprot_4k_2_large(prot);