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>
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 @@ /* * 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 @@ #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 @@ #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 @@ /* * 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 @@ *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 @@ * 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 @@ 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 @@ 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 @@ /* * 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 @@ } #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 @@ 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 @@ 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 @@ 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)) {