[tip:x86/mm] x86/mm/mtrr: Use symbolic define as a retval for disabled MTRRs

tip-bot for Toshi Kani
2015-05-27T14:19:35Z

Commit-ID: 3d3ca416d9b0784cfcf244eeeba1bcaf421bc64d
Gitweb: http://git.kernel.org/tip/3d3ca416d9b0784cfcf244eeeba1bcaf421bc64d
Author: Toshi Kani <toshi.kani@hp.com>
AuthorDate: Tue, 26 May 2015 10:28:07 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 27 May 2015 14:40:57 +0200

x86/mm/mtrr: Use symbolic define as a retval for disabled MTRRs

mtrr_type_lookup() returns verbatim 0xFF when MTRRs are
disabled. This patch defines MTRR_TYPE_INVALID to clarify the
meaning of this value, and documents its usage.

Document the return values of the kernel virtual address mapping
helpers pud_set_huge(), pmd_set_huge, pud_clear_huge() and
pmd_clear_huge().

There is no functional change in this patch.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
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/1431714237-880-5-git-send-email-toshi.kani@hp.com
Link: http://lkml.kernel.org/r/1432628901-18044-5-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/mtrr.h | 2 +-
arch/x86/include/uapi/asm/mtrr.h | 8 +++++++-
arch/x86/kernel/cpu/mtrr/generic.c | 14 ++++++-------
arch/x86/mm/pgtable.c | 42 +++++++++++++++++++++++++++++---------
4 files changed, 47 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
index ef92794..bb03a54 100644
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -55,7 +55,7 @@ static inline u8 mtrr_type_lookup(u64 addr, u64 end)
/*
* Return no-MTRRs:
*/
- return 0xff;
+ return MTRR_TYPE_INVALID;
}
#define mtrr_save_fixed_ranges(arg) do {} while (0)
#define mtrr_save_state() do {} while (0)
diff --git a/arch/x86/include/uapi/asm/mtrr.h b/arch/x86/include/uapi/asm/mtrr.h
index d0acb65..7528dcf 100644
--- a/arch/x86/include/uapi/asm/mtrr.h
+++ b/arch/x86/include/uapi/asm/mtrr.h
@@ -103,7 +103,7 @@ struct mtrr_state_type {
#define MTRRIOC_GET_PAGE_ENTRY _IOWR(MTRR_IOCTL_BASE, 8, struct mtrr_gentry)
#define MTRRIOC_KILL_PAGE_ENTRY _IOW(MTRR_IOCTL_BASE, 9, struct mtrr_sentry)

-/* These are the region types */
+/* MTRR memory types, which are defined in SDM */
#define MTRR_TYPE_UNCACHABLE 0
#define MTRR_TYPE_WRCOMB 1
/*#define MTRR_TYPE_ 2*/
@@ -113,5 +113,11 @@ struct mtrr_state_type {
#define MTRR_TYPE_WRBACK 6
#define MTRR_NUM_TYPES 7

+/*
+ * Invalid MTRR memory type. mtrr_type_lookup() returns this value when
+ * MTRRs are disabled. Note, this value is allocated from the reserved
+ * values (0x7-0xff) of the MTRR memory types.
+ */
+#define MTRR_TYPE_INVALID 0xff

#endif /* _UAPI_ASM_X86_MTRR_H */
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index b0599db..7b1491c 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -104,7 +104,7 @@ static int check_type_overlap(u8 *prev, u8 *curr)

/*
* Error/Semi-error returns:
- * 0xFF - when MTRR is not enabled
+ * MTRR_TYPE_INVALID - when MTRR is not enabled
* *repeat == 1 implies [start:end] spanned across MTRR range and type returned
* corresponds only to [start:*partial_end].
* Caller has to lookup again for [*partial_end:end].
@@ -117,10 +117,10 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)

*repeat = 0;
if (!mtrr_state_set)
- return 0xFF;
+ return MTRR_TYPE_INVALID;

if (!(mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED))
- return 0xFF;
+ return MTRR_TYPE_INVALID;

/* Make end inclusive end, instead of exclusive */
end--;
@@ -151,7 +151,7 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)
* Look of multiple ranges matching this address and pick type
* as per MTRR precedence
*/
- prev_match = 0xFF;
+ prev_match = MTRR_TYPE_INVALID;
for (i = 0; i < num_var_ranges; ++i) {
unsigned short start_state, end_state, inclusive;

@@ -206,7 +206,7 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)
continue;

curr_match = mtrr_state.var_ranges[i].base_lo & 0xff;
- if (prev_match == 0xFF) {
+ if (prev_match == MTRR_TYPE_INVALID) {
prev_match = curr_match;
continue;
}
@@ -220,7 +220,7 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)
return MTRR_TYPE_WRBACK;
}

- if (prev_match != 0xFF)
+ if (prev_match != MTRR_TYPE_INVALID)
return prev_match;

return mtrr_state.def_type;
@@ -229,7 +229,7 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)
/*
* Returns the effective MTRR type for the region
* Error return:
- * 0xFF - when MTRR is not enabled
+ * MTRR_TYPE_INVALID - when MTRR is not enabled
*/
u8 mtrr_type_lookup(u64 start, u64 end)
{
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 0b97d2c..c30f981 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -563,16 +563,22 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
}

#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
+/**
+ * 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.
+ *
+ * Returns 1 on success and 0 on failure.
+ */
int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
{
u8 mtrr;

- /*
- * Do not use a huge page when the range is covered by non-WB type
- * of MTRRs.
- */
mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE);
- if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
+ if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != MTRR_TYPE_INVALID))
return 0;

prot = pgprot_4k_2_large(prot);
@@ -584,16 +590,22 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
return 1;
}

+/**
+ * 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.
+ *
+ * Returns 1 on success and 0 on failure.
+ */
int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
{
u8 mtrr;

- /*
- * Do not use a huge page when the range is covered by non-WB type
- * of MTRRs.
- */
mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE);
- if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
+ if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != MTRR_TYPE_INVALID))
return 0;

prot = pgprot_4k_2_large(prot);
@@ -605,6 +617,11 @@ int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
return 1;
}

+/**
+ * pud_clear_huge - clear kernel PUD mapping when it is set
+ *
+ * Returns 1 on success and 0 on failure (no PUD map is found).
+ */
int pud_clear_huge(pud_t *pud)
{
if (pud_large(*pud)) {
@@ -615,6 +632,11 @@ int pud_clear_huge(pud_t *pud)
return 0;
}

+/**
+ * pmd_clear_huge - clear kernel PMD mapping when it is set
+ *
+ * Returns 1 on success and 0 on failure (no PMD map is found).
+ */
int pmd_clear_huge(pmd_t *pmd)
{
if (pmd_large(*pmd)) {