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x86/mm/mtrr: Enhance MTRR checks in kernel mapping helpers

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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>
This commit is contained in:
Toshi Kani
2015-05-26 10:28:10 +02:00
committed by Ingo Molnar
parent 0cc705f56e
commit b73522e0c1
4 changed files with 58 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
arch/x86/mm/pgtable.c
View File

@@ -566,19 +566,28 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
/**
* 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 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
/**
* 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);