diff options
| -rw-r--r-- | arch/x86/Kconfig.debug | 19 | ||||
| -rw-r--r-- | arch/x86/mm/tlb.c | 51 |
2 files changed, 70 insertions, 0 deletions
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index e46c2147397f..b322f124ee3c 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -129,6 +129,25 @@ config DOUBLEFAULT option saves about 4k and might cause you much additional grey hair. +config DEBUG_TLBFLUSH + bool "Set upper limit of TLB entries to flush one-by-one" + depends on DEBUG_KERNEL && (X86_64 || X86_INVLPG) + ---help--- + + X86-only for now. + + This option allows the user to tune the amount of TLB entries the + kernel flushes one-by-one instead of doing a full TLB flush. In + certain situations, the former is cheaper. This is controlled by the + tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it + to -1, the code flushes the whole TLB unconditionally. Otherwise, + for positive values of it, the kernel will use single TLB entry + invalidating instructions according to the following formula: + + flush_entries <= active_tlb_entries / 2^tlb_flushall_shift + + If in doubt, say "N". + config IOMMU_DEBUG bool "Enable IOMMU debugging" depends on GART_IOMMU && DEBUG_KERNEL diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 2939f2f9edbb..5911f61e300e 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -12,6 +12,7 @@ #include <asm/cache.h> #include <asm/apic.h> #include <asm/uv/uv.h> +#include <linux/debugfs.h> DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate) = { &init_mm, 0, }; @@ -430,3 +431,53 @@ void flush_tlb_all(void) { on_each_cpu(do_flush_tlb_all, NULL, 1); } + +#ifdef CONFIG_DEBUG_TLBFLUSH +static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf, + size_t count, loff_t *ppos) +{ + char buf[32]; + unsigned int len; + + len = sprintf(buf, "%hd\n", tlb_flushall_shift); + return simple_read_from_buffer(user_buf, count, ppos, buf, len); +} + +static ssize_t tlbflush_write_file(struct file *file, + const char __user *user_buf, size_t count, loff_t *ppos) +{ + char buf[32]; + ssize_t len; + s8 shift; + + len = min(count, sizeof(buf) - 1); + if (copy_from_user(buf, user_buf, len)) + return -EFAULT; + + buf[len] = '\0'; + if (kstrtos8(buf, 0, &shift)) + return -EINVAL; + + if (shift > 64) + return -EINVAL; + + tlb_flushall_shift = shift; + return count; +} + +static const struct file_operations fops_tlbflush = { + .read = tlbflush_read_file, + .write = tlbflush_write_file, + .llseek = default_llseek, +}; + +static int __cpuinit create_tlb_flushall_shift(void) +{ + if (cpu_has_invlpg) { + debugfs_create_file("tlb_flushall_shift", S_IRUSR | S_IWUSR, + arch_debugfs_dir, NULL, &fops_tlbflush); + } + return 0; +} +late_initcall(create_tlb_flushall_shift); +#endif |