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Date: Fri, 15 May 2015 12:23:55 -0600
From: Toshi Kani <toshi.kani@...com>
To: bp@...en8.de, akpm@...ux-foundation.org, hpa@...or.com,
tglx@...utronix.de, mingo@...hat.com
Cc: linux-mm@...ck.org, x86@...nel.org, linux-kernel@...r.kernel.org,
dave.hansen@...el.com, Elliott@...com, pebolle@...cali.nl,
mcgrof@...e.com, Toshi Kani <toshi.kani@...com>
Subject: [PATCH v5 4/6] mtrr, x86: Define MTRR_TYPE_INVALID for mtrr_type_lookup()
mtrr_type_lookup() returns 0xFF when it cannot return a valid
MTRR memory type since 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 Kernel Virtual Address mapping
functions, 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@...com>
---
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)) {
--
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