diff options
| -rw-r--r-- | arch/x86/boot/compressed/mem_encrypt.S | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/sev-es-shared.c | 6 | ||||
| -rw-r--r-- | arch/x86/mm/mem_encrypt_identity.c | 35 |
3 files changed, 20 insertions, 27 deletions
diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S index aa561795efd1..a6dea4e8a082 100644 --- a/arch/x86/boot/compressed/mem_encrypt.S +++ b/arch/x86/boot/compressed/mem_encrypt.S @@ -23,12 +23,6 @@ SYM_FUNC_START(get_sev_encryption_bit) push %ecx push %edx - /* Check if running under a hypervisor */ - movl $1, %eax - cpuid - bt $31, %ecx /* Check the hypervisor bit */ - jnc .Lno_sev - movl $0x80000000, %eax /* CPUID to check the highest leaf */ cpuid cmpl $0x8000001f, %eax /* See if 0x8000001f is available */ diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c index cdc04d091242..387b71669818 100644 --- a/arch/x86/kernel/sev-es-shared.c +++ b/arch/x86/kernel/sev-es-shared.c @@ -186,7 +186,6 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) * make it accessible to the hypervisor. * * In particular, check for: - * - Hypervisor CPUID bit * - Availability of CPUID leaf 0x8000001f * - SEV CPUID bit. * @@ -194,10 +193,7 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) * can't be checked here. */ - if ((fn == 1 && !(regs->cx & BIT(31)))) - /* Hypervisor bit */ - goto fail; - else if (fn == 0x80000000 && (regs->ax < 0x8000001f)) + if (fn == 0x80000000 && (regs->ax < 0x8000001f)) /* SEV leaf check */ goto fail; else if ((fn == 0x8000001f && !(regs->ax & BIT(1)))) diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c index 6c5eb6f3f14f..a19374d26101 100644 --- a/arch/x86/mm/mem_encrypt_identity.c +++ b/arch/x86/mm/mem_encrypt_identity.c @@ -503,14 +503,10 @@ void __init sme_enable(struct boot_params *bp) #define AMD_SME_BIT BIT(0) #define AMD_SEV_BIT BIT(1) - /* - * Set the feature mask (SME or SEV) based on whether we are - * running under a hypervisor. - */ - eax = 1; - ecx = 0; - native_cpuid(&eax, &ebx, &ecx, &edx); - feature_mask = (ecx & BIT(31)) ? AMD_SEV_BIT : AMD_SME_BIT; + + /* Check the SEV MSR whether SEV or SME is enabled */ + sev_status = __rdmsr(MSR_AMD64_SEV); + feature_mask = (sev_status & MSR_AMD64_SEV_ENABLED) ? AMD_SEV_BIT : AMD_SME_BIT; /* * Check for the SME/SEV feature: @@ -530,19 +526,26 @@ void __init sme_enable(struct boot_params *bp) /* Check if memory encryption is enabled */ if (feature_mask == AMD_SME_BIT) { + /* + * No SME if Hypervisor bit is set. This check is here to + * prevent a guest from trying to enable SME. For running as a + * KVM guest the MSR_K8_SYSCFG will be sufficient, but there + * might be other hypervisors which emulate that MSR as non-zero + * or even pass it through to the guest. + * A malicious hypervisor can still trick a guest into this + * path, but there is no way to protect against that. + */ + eax = 1; + ecx = 0; + native_cpuid(&eax, &ebx, &ecx, &edx); + if (ecx & BIT(31)) + return; + /* For SME, check the SYSCFG MSR */ msr = __rdmsr(MSR_K8_SYSCFG); if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT)) return; } else { - /* For SEV, check the SEV MSR */ - msr = __rdmsr(MSR_AMD64_SEV); - if (!(msr & MSR_AMD64_SEV_ENABLED)) - return; - - /* Save SEV_STATUS to avoid reading MSR again */ - sev_status = msr; - /* SEV state cannot be controlled by a command line option */ sme_me_mask = me_mask; sev_enabled = true; |