Messages in this thread Patch in this message | | | From | Jacob Pan <> | Subject | [PATCH] x86: add workaround monitor bug | Date | Wed, 6 Jul 2016 10:01:54 -0700 |
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From: Peter Zijlstra <peterz@infradead.org>
Monitored cached line may not wake up from mwait on certain Goldmont based CPUs. This patch will avoid calling current_set_polling_and_test() and thereby not set the TIF_ flag. The result is that we'll always send IPIs for wakeups.
Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/mwait.h | 2 +- arch/x86/kernel/cpu/intel.c | 5 +++++ arch/x86/kernel/process.c | 2 +- 4 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 78dbd28..197a3f4 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -304,6 +304,7 @@ #define X86_BUG_SYSRET_SS_ATTRS X86_BUG(8) /* SYSRET doesn't fix up SS attrs */ #define X86_BUG_NULL_SEG X86_BUG(9) /* Nulling a selector preserves the base */ #define X86_BUG_SWAPGS_FENCE X86_BUG(10) /* SWAPGS without input dep on GS */ +#define X86_BUG_MONITOR X86_BUG(11) /* IPI required to wake up remote cpu */ #ifdef CONFIG_X86_32 diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 0deeb2d..f37f2d8 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -97,7 +97,7 @@ static inline void __sti_mwait(unsigned long eax, unsigned long ecx) */ static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx) { - if (!current_set_polling_and_test()) { + if (static_cpu_has_bug(X86_BUG_MONITOR) || !current_set_polling_and_test()) { if (static_cpu_has_bug(X86_BUG_CLFLUSH_MONITOR)) { mb(); clflush((void *)¤t_thread_info()->flags); diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 6e2ffbe..77c6b3e 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -13,6 +13,7 @@ #include <asm/msr.h> #include <asm/bugs.h> #include <asm/cpu.h> +#include <asm/intel-family.h> #ifdef CONFIG_X86_64 #include <linux/topology.h> @@ -509,6 +510,10 @@ static void init_intel(struct cpuinfo_x86 *c) (c->x86_model == 29 || c->x86_model == 46 || c->x86_model == 47)) set_cpu_bug(c, X86_BUG_CLFLUSH_MONITOR); + if (c->x86 == 6 && boot_cpu_has(X86_FEATURE_MWAIT) && + ((c->x86_model == INTEL_FAM6_ATOM_GOLDMONT))) + set_cpu_bug(c, X86_BUG_MONITOR); + #ifdef CONFIG_X86_64 if (c->x86 == 15) c->x86_cache_alignment = c->x86_clflush_size * 2; diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 96becbb..59f68f1 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -404,7 +404,7 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) if (c->x86_vendor != X86_VENDOR_INTEL) return 0; - if (!cpu_has(c, X86_FEATURE_MWAIT)) + if (!cpu_has(c, X86_FEATURE_MWAIT) || static_cpu_has_bug(X86_BUG_MONITOR)) return 0; return 1; -- 1.9.1
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