diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0057-x86-cpu-AMD-Use-LFENCE_RDTSC-in-preference-to-MFENCE.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0057-x86-cpu-AMD-Use-LFENCE_RDTSC-in-preference-to-MFENCE.patch | 86 |
1 files changed, 0 insertions, 86 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0057-x86-cpu-AMD-Use-LFENCE_RDTSC-in-preference-to-MFENCE.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0057-x86-cpu-AMD-Use-LFENCE_RDTSC-in-preference-to-MFENCE.patch deleted file mode 100644 index faad5ca4..00000000 --- a/common/recipes-kernel/linux/linux-yocto-4.9.21/0057-x86-cpu-AMD-Use-LFENCE_RDTSC-in-preference-to-MFENCE.patch +++ /dev/null @@ -1,86 +0,0 @@ -From f2abe3ce255832f6ee98887777b25b58cfcc9015 Mon Sep 17 00:00:00 2001 -From: Tom Lendacky <thomas.lendacky@amd.com> -Date: Mon, 8 Jan 2018 16:09:32 -0600 -Subject: [PATCH 057/103] x86/cpu/AMD: Use LFENCE_RDTSC in preference to - MFENCE_RDTSC - -commit 9c6a73c75864ad9fa49e5fa6513e4c4071c0e29f upstream. - -With LFENCE now a serializing instruction, use LFENCE_RDTSC in preference -to MFENCE_RDTSC. However, since the kernel could be running under a -hypervisor that does not support writing that MSR, read the MSR back and -verify that the bit has been set successfully. If the MSR can be read -and the bit is set, then set the LFENCE_RDTSC feature, otherwise set the -MFENCE_RDTSC feature. - -Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> -Signed-off-by: Thomas Gleixner <tglx@linutronix.de> -Reviewed-by: Reviewed-by: Borislav Petkov <bp@suse.de> -Cc: Peter Zijlstra <peterz@infradead.org> -Cc: Tim Chen <tim.c.chen@linux.intel.com> -Cc: Dave Hansen <dave.hansen@intel.com> -Cc: Borislav Petkov <bp@alien8.de> -Cc: Dan Williams <dan.j.williams@intel.com> -Cc: Linus Torvalds <torvalds@linux-foundation.org> -Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org> -Cc: David Woodhouse <dwmw@amazon.co.uk> -Cc: Paul Turner <pjt@google.com> -Link: https://lkml.kernel.org/r/20180108220932.12580.52458.stgit@tlendack-t1.amdoffice.net -Signed-off-by: Razvan Ghitulete <rga@amazon.de> -Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> ---- - arch/x86/include/asm/msr-index.h | 1 + - arch/x86/kernel/cpu/amd.c | 18 ++++++++++++++++-- - 2 files changed, 17 insertions(+), 2 deletions(-) - -diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h -index b1c0969..4eeaa36 100644 ---- a/arch/x86/include/asm/msr-index.h -+++ b/arch/x86/include/asm/msr-index.h -@@ -332,6 +332,7 @@ - #define MSR_FAM10H_NODE_ID 0xc001100c - #define MSR_F10H_DECFG 0xc0011029 - #define MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT 1 -+#define MSR_F10H_DECFG_LFENCE_SERIALIZE BIT_ULL(MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT) - - /* K8 MSRs */ - #define MSR_K8_TOP_MEM1 0xc001001a -diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c -index 8b5b19d..1b89f0c 100644 ---- a/arch/x86/kernel/cpu/amd.c -+++ b/arch/x86/kernel/cpu/amd.c -@@ -782,6 +782,9 @@ static void init_amd(struct cpuinfo_x86 *c) - set_cpu_cap(c, X86_FEATURE_K8); - - if (cpu_has(c, X86_FEATURE_XMM2)) { -+ unsigned long long val; -+ int ret; -+ - /* - * A serializing LFENCE has less overhead than MFENCE, so - * use it for execution serialization. On families which -@@ -792,8 +795,19 @@ static void init_amd(struct cpuinfo_x86 *c) - msr_set_bit(MSR_F10H_DECFG, - MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT); - -- /* MFENCE stops RDTSC speculation */ -- set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC); -+ /* -+ * Verify that the MSR write was successful (could be running -+ * under a hypervisor) and only then assume that LFENCE is -+ * serializing. -+ */ -+ ret = rdmsrl_safe(MSR_F10H_DECFG, &val); -+ if (!ret && (val & MSR_F10H_DECFG_LFENCE_SERIALIZE)) { -+ /* A serializing LFENCE stops RDTSC speculation */ -+ set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC); -+ } else { -+ /* MFENCE stops RDTSC speculation */ -+ set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC); -+ } - } - - /* --- -2.7.4 - |