diff options
| -rw-r--r-- | arch/x86/include/asm/io.h | 7 | ||||
| -rw-r--r-- | arch/x86/include/asm/mtrr.h | 10 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/mtrr/main.c | 71 | ||||
| -rw-r--r-- | include/linux/io.h | 25 |
4 files changed, 112 insertions, 1 deletions
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index d8e8eefbe24c..34f69cb9350a 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -345,4 +345,11 @@ extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1, #define IO_SPACE_LIMIT 0xffff +#ifdef CONFIG_MTRR +extern int __must_check arch_phys_wc_add(unsigned long base, + unsigned long size); +extern void arch_phys_wc_del(int handle); +#define arch_phys_wc_add arch_phys_wc_add +#endif + #endif /* _ASM_X86_IO_H */ diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h index e235582f9930..f768f6298419 100644 --- a/arch/x86/include/asm/mtrr.h +++ b/arch/x86/include/asm/mtrr.h @@ -26,7 +26,10 @@ #include <uapi/asm/mtrr.h> -/* The following functions are for use by other drivers */ +/* + * The following functions are for use by other drivers that cannot use + * arch_phys_wc_add and arch_phys_wc_del. + */ # ifdef CONFIG_MTRR extern u8 mtrr_type_lookup(u64 addr, u64 end); extern void mtrr_save_fixed_ranges(void *); @@ -45,6 +48,7 @@ extern void mtrr_aps_init(void); extern void mtrr_bp_restore(void); extern int mtrr_trim_uncached_memory(unsigned long end_pfn); extern int amd_special_default_mtrr(void); +extern int phys_wc_to_mtrr_index(int handle); # else static inline u8 mtrr_type_lookup(u64 addr, u64 end) { @@ -80,6 +84,10 @@ static inline int mtrr_trim_uncached_memory(unsigned long end_pfn) static inline void mtrr_centaur_report_mcr(int mcr, u32 lo, u32 hi) { } +static inline int phys_wc_to_mtrr_index(int handle) +{ + return -1; +} #define mtrr_ap_init() do {} while (0) #define mtrr_bp_init() do {} while (0) diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c index 726bf963c227..3533d4d16f8c 100644 --- a/arch/x86/kernel/cpu/mtrr/main.c +++ b/arch/x86/kernel/cpu/mtrr/main.c @@ -51,9 +51,13 @@ #include <asm/e820.h> #include <asm/mtrr.h> #include <asm/msr.h> +#include <asm/pat.h> #include "mtrr.h" +/* arch_phys_wc_add returns an MTRR register index plus this offset. */ +#define MTRR_TO_PHYS_WC_OFFSET 1000 + u32 num_var_ranges; unsigned int mtrr_usage_table[MTRR_MAX_VAR_RANGES]; @@ -524,6 +528,73 @@ int mtrr_del(int reg, unsigned long base, unsigned long size) } EXPORT_SYMBOL(mtrr_del); +/** + * arch_phys_wc_add - add a WC MTRR and handle errors if PAT is unavailable + * @base: Physical base address + * @size: Size of region + * + * If PAT is available, this does nothing. If PAT is unavailable, it + * attempts to add a WC MTRR covering size bytes starting at base and + * logs an error if this fails. + * + * Drivers must store the return value to pass to mtrr_del_wc_if_needed, + * but drivers should not try to interpret that return value. + */ +int arch_phys_wc_add(unsigned long base, unsigned long size) +{ + int ret; + + if (pat_enabled) + return 0; /* Success! (We don't need to do anything.) */ + + ret = mtrr_add(base, size, MTRR_TYPE_WRCOMB, true); + if (ret < 0) { + pr_warn("Failed to add WC MTRR for [%p-%p]; performance may suffer.", + (void *)base, (void *)(base + size - 1)); + return ret; + } + return ret + MTRR_TO_PHYS_WC_OFFSET; +} +EXPORT_SYMBOL(arch_phys_wc_add); + +/* + * arch_phys_wc_del - undoes arch_phys_wc_add + * @handle: Return value from arch_phys_wc_add + * + * This cleans up after mtrr_add_wc_if_needed. + * + * The API guarantees that mtrr_del_wc_if_needed(error code) and + * mtrr_del_wc_if_needed(0) do nothing. + */ +void arch_phys_wc_del(int handle) +{ + if (handle >= 1) { + WARN_ON(handle < MTRR_TO_PHYS_WC_OFFSET); + mtrr_del(handle - MTRR_TO_PHYS_WC_OFFSET, 0, 0); + } +} +EXPORT_SYMBOL(arch_phys_wc_del); + +/* + * phys_wc_to_mtrr_index - translates arch_phys_wc_add's return value + * @handle: Return value from arch_phys_wc_add + * + * This will turn the return value from arch_phys_wc_add into an mtrr + * index suitable for debugging. + * + * Note: There is no legitimate use for this function, except possibly + * in printk line. Alas there is an illegitimate use in some ancient + * drm ioctls. + */ +int phys_wc_to_mtrr_index(int handle) +{ + if (handle < MTRR_TO_PHYS_WC_OFFSET) + return -1; + else + return handle - MTRR_TO_PHYS_WC_OFFSET; +} +EXPORT_SYMBOL_GPL(phys_wc_to_mtrr_index); + /* * HACK ALERT! * These should be called implicitly, but we can't yet until all the initcall diff --git a/include/linux/io.h b/include/linux/io.h index 069e4075f872..f4f42faec686 100644 --- a/include/linux/io.h +++ b/include/linux/io.h @@ -76,4 +76,29 @@ void devm_ioremap_release(struct device *dev, void *res); #define arch_has_dev_port() (1) #endif +/* + * Some systems (x86 without PAT) have a somewhat reliable way to mark a + * physical address range such that uncached mappings will actually + * end up write-combining. This facility should be used in conjunction + * with pgprot_writecombine, ioremap-wc, or set_memory_wc, since it has + * no effect if the per-page mechanisms are functional. + * (On x86 without PAT, these functions manipulate MTRRs.) + * + * arch_phys_del_wc(0) or arch_phys_del_wc(any error code) is guaranteed + * to have no effect. + */ +#ifndef arch_phys_wc_add +static inline int __must_check arch_phys_wc_add(unsigned long base, + unsigned long size) +{ + return 0; /* It worked (i.e. did nothing). */ +} + +static inline void arch_phys_wc_del(int handle) +{ +} + +#define arch_phys_wc_add arch_phys_wc_add +#endif + #endif /* _LINUX_IO_H */ |