4.9-stable review patch. If anyone has any objections, please let me know.
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From: Tom Lendacky thomas.lendacky@amd.com
commit 11fb0683493b2da112cd64c9dada221b52463bf7 upstream
Some AMD processors only support a non-architectural means of enabling speculative store bypass disable (SSBD). To allow a simplified view of this to a guest, an architectural definition has been created through a new CPUID bit, 0x80000008_EBX[25], and a new MSR, 0xc001011f. With this, a hypervisor can virtualize the existence of this definition and provide an architectural method for using SSBD to a guest.
Add the new CPUID feature, the new MSR and update the existing SSBD support to use this MSR when present.
Signed-off-by: Tom Lendacky thomas.lendacky@amd.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Borislav Petkov bp@suse.de Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/msr-index.h | 2 ++ arch/x86/kernel/cpu/bugs.c | 4 +++- arch/x86/kernel/process.c | 13 ++++++++++++- 4 files changed, 18 insertions(+), 2 deletions(-)
--- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -274,6 +274,7 @@ #define X86_FEATURE_AMD_IBPB (13*32+12) /* Indirect Branch Prediction Barrier */ #define X86_FEATURE_AMD_IBRS (13*32+14) /* Indirect Branch Restricted Speculation */ #define X86_FEATURE_AMD_STIBP (13*32+15) /* Single Thread Indirect Branch Predictors */ +#define X86_FEATURE_VIRT_SSBD (13*32+25) /* Virtualized Speculative Store Bypass Disable */
/* Thermal and Power Management Leaf, CPUID level 0x00000006 (eax), word 14 */ #define X86_FEATURE_DTHERM (14*32+ 0) /* Digital Thermal Sensor */ --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -323,6 +323,8 @@ #define MSR_AMD64_IBSOPDATA4 0xc001103d #define MSR_AMD64_IBS_REG_COUNT_MAX 8 /* includes MSR_AMD64_IBSBRTARGET */
+#define MSR_AMD64_VIRT_SPEC_CTRL 0xc001011f + /* Fam 17h MSRs */ #define MSR_F17H_IRPERF 0xc00000e9
--- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -204,7 +204,9 @@ static void x86_amd_ssb_disable(void) { u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask;
- if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD)) + if (boot_cpu_has(X86_FEATURE_VIRT_SSBD)) + wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD); + else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD)) wrmsrl(MSR_AMD64_LS_CFG, msrval); }
--- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -312,6 +312,15 @@ static __always_inline void amd_set_core } #endif
+static __always_inline void amd_set_ssb_virt_state(unsigned long tifn) +{ + /* + * SSBD has the same definition in SPEC_CTRL and VIRT_SPEC_CTRL, + * so ssbd_tif_to_spec_ctrl() just works. + */ + wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, ssbd_tif_to_spec_ctrl(tifn)); +} + static __always_inline void intel_set_ssb_state(unsigned long tifn) { u64 msr = x86_spec_ctrl_base | ssbd_tif_to_spec_ctrl(tifn); @@ -321,7 +330,9 @@ static __always_inline void intel_set_ss
static __always_inline void __speculative_store_bypass_update(unsigned long tifn) { - if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) + if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) + amd_set_ssb_virt_state(tifn); + else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) amd_set_core_ssb_state(tifn); else intel_set_ssb_state(tifn);