From 20c28c04a6bc2ebd60fa20e5c3a6bf3bfa736d81 Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Mon, 8 Jan 2018 16:09:21 -0600 Subject: x86/cpu/AMD: Make LFENCE a serializing instruction commit e4d0e84e490790798691aaa0f2e598637f1867ec upstream. To aid in speculation control, make LFENCE a serializing instruction since it has less overhead than MFENCE. This is done by setting bit 1 of MSR 0xc0011029 (DE_CFG). Some families that support LFENCE do not have this MSR. For these families, the LFENCE instruction is already serializing. Signed-off-by: Tom Lendacky Signed-off-by: Thomas Gleixner Reviewed-by: Reviewed-by: Borislav Petkov Cc: Peter Zijlstra Cc: Tim Chen Cc: Dave Hansen Cc: Borislav Petkov Cc: Dan Williams Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: David Woodhouse Cc: Paul Turner Link: https://lkml.kernel.org/r/20180108220921.12580.71694.stgit@tlendack-t1.amdoffice.net Signed-off-by: Razvan Ghitulete Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/msr-index.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/include/asm/msr-index.h') diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index 37db36fddc88..f00dfff81370 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -330,6 +330,8 @@ #define FAM10H_MMIO_CONF_BASE_MASK 0xfffffffULL #define FAM10H_MMIO_CONF_BASE_SHIFT 20 #define MSR_FAM10H_NODE_ID 0xc001100c +#define MSR_F10H_DECFG 0xc0011029 +#define MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT 1 /* K8 MSRs */ #define MSR_K8_TOP_MEM1 0xc001001a -- cgit v1.2.3 From 642ce1bb5ea64b1d036dff04a005d9bbe28ab5b4 Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Mon, 8 Jan 2018 16:09:32 -0600 Subject: 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 Signed-off-by: Thomas Gleixner Reviewed-by: Reviewed-by: Borislav Petkov Cc: Peter Zijlstra Cc: Tim Chen Cc: Dave Hansen Cc: Borislav Petkov Cc: Dan Williams Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: David Woodhouse Cc: Paul Turner Link: https://lkml.kernel.org/r/20180108220932.12580.52458.stgit@tlendack-t1.amdoffice.net Signed-off-by: Razvan Ghitulete Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/msr-index.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/include/asm/msr-index.h') diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index f00dfff81370..b8911aecf035 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 -- cgit v1.2.3