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| author | Borislav Petkov (AMD) <bp@alien8.de> | 2023-07-07 13:53:41 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-08-08 20:03:50 +0200 |
| commit | c9ae63d773ca182c4ef63fbdd22cdf090d9c1cd7 (patch) | |
| tree | 1c2aecf6141d7e776f99551cd3228623fa53d52e /arch | |
| parent | 79c8091888ef61aac79ef72122d1e6cd0b620669 (diff) | |
| download | linux-c9ae63d773ca182c4ef63fbdd22cdf090d9c1cd7.tar.gz | |
x86/srso: Add IBPB on VMEXIT
Upstream commit: d893832d0e1ef41c72cdae444268c1d64a2be8ad Add the option to flush IBPB only on VMEXIT in order to protect from malicious guests but one otherwise trusts the software that runs on the hypervisor. Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/cpufeatures.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 19 | ||||
| -rw-r--r-- | arch/x86/kvm/svm/svm.c | 4 | ||||
| -rw-r--r-- | arch/x86/kvm/svm/vmenter.S | 3 |
4 files changed, 26 insertions, 1 deletions
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index a8c2733c816c..e721b8426c24 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -310,6 +310,7 @@ #define X86_FEATURE_SRSO (11*32+24) /* "" AMD BTB untrain RETs */ #define X86_FEATURE_SRSO_ALIAS (11*32+25) /* "" AMD BTB untrain RETs through aliasing */ +#define X86_FEATURE_IBPB_ON_VMEXIT (11*32+26) /* "" Issue an IBPB only on VMEXIT */ /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */ #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 82417ce310cc..af612778a328 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -2316,6 +2316,7 @@ enum srso_mitigation { SRSO_MITIGATION_MICROCODE, SRSO_MITIGATION_SAFE_RET, SRSO_MITIGATION_IBPB, + SRSO_MITIGATION_IBPB_ON_VMEXIT, }; enum srso_mitigation_cmd { @@ -2323,6 +2324,7 @@ enum srso_mitigation_cmd { SRSO_CMD_MICROCODE, SRSO_CMD_SAFE_RET, SRSO_CMD_IBPB, + SRSO_CMD_IBPB_ON_VMEXIT, }; static const char * const srso_strings[] = { @@ -2330,6 +2332,7 @@ static const char * const srso_strings[] = { [SRSO_MITIGATION_MICROCODE] = "Mitigation: microcode", [SRSO_MITIGATION_SAFE_RET] = "Mitigation: safe RET", [SRSO_MITIGATION_IBPB] = "Mitigation: IBPB", + [SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only" }; static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE; @@ -2348,6 +2351,8 @@ static int __init srso_parse_cmdline(char *str) srso_cmd = SRSO_CMD_SAFE_RET; else if (!strcmp(str, "ibpb")) srso_cmd = SRSO_CMD_IBPB; + else if (!strcmp(str, "ibpb-vmexit")) + srso_cmd = SRSO_CMD_IBPB_ON_VMEXIT; else pr_err("Ignoring unknown SRSO option (%s).", str); @@ -2431,6 +2436,20 @@ static void __init srso_select_mitigation(void) pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n"); goto pred_cmd; } + break; + + case SRSO_CMD_IBPB_ON_VMEXIT: + if (IS_ENABLED(CONFIG_CPU_SRSO)) { + if (!boot_cpu_has(X86_FEATURE_ENTRY_IBPB) && has_microcode) { + setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT); + srso_mitigation = SRSO_MITIGATION_IBPB_ON_VMEXIT; + } + } else { + pr_err("WARNING: kernel not compiled with CPU_SRSO.\n"); + goto pred_cmd; + } + break; + default: break; } diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 0a212fe2cd39..fdb6007f2eb8 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1485,7 +1485,9 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if (sd->current_vmcb != svm->vmcb) { sd->current_vmcb = svm->vmcb; - indirect_branch_prediction_barrier(); + + if (!cpu_feature_enabled(X86_FEATURE_IBPB_ON_VMEXIT)) + indirect_branch_prediction_barrier(); } if (kvm_vcpu_apicv_active(vcpu)) avic_vcpu_load(vcpu, cpu); diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S index 34367dc203f2..5be9a63f09ff 100644 --- a/arch/x86/kvm/svm/vmenter.S +++ b/arch/x86/kvm/svm/vmenter.S @@ -223,6 +223,9 @@ SYM_FUNC_START(__svm_vcpu_run) */ UNTRAIN_RET + /* SRSO */ + ALTERNATIVE "", "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT + /* * Clear all general purpose registers except RSP and RAX to prevent * speculative use of the guest's values, even those that are reloaded |