From: Pawan Gupta TSA mitigation: d8010d4ba43e ("x86/bugs: Add a Transient Scheduler Attacks mitigation") introduced VM_CLEAR_CPU_BUFFERS for guests on AMD CPUs. Currently on Intel CLEAR_CPU_BUFFERS is being used for guests which has a much broader scope (kernel->user also). Make mitigations on Intel consistent with TSA. This would help handling the guest-only mitigations better in future. Signed-off-by: Pawan Gupta [sean: make CLEAR_CPU_BUF_VM mutually exclusive with the MMIO mitigation] Acked-by: Borislav Petkov (AMD) Signed-off-by: Sean Christopherson --- arch/x86/kernel/cpu/bugs.c | 13 +++++++++---- arch/x86/kvm/vmx/vmenter.S | 2 +- 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index d7fa03bf51b4..c3a26532a209 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -194,7 +194,7 @@ DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush); /* * Controls CPU Fill buffer clear before VMenter. This is a subset of - * X86_FEATURE_CLEAR_CPU_BUF, and should only be enabled when KVM-only + * X86_FEATURE_CLEAR_CPU_BUF_VM, and should only be enabled when KVM-only * mitigation is required. */ DEFINE_STATIC_KEY_FALSE(cpu_buf_vm_clear); @@ -489,8 +489,8 @@ static enum rfds_mitigations rfds_mitigation __ro_after_init = IS_ENABLED(CONFIG_MITIGATION_RFDS) ? RFDS_MITIGATION_AUTO : RFDS_MITIGATION_OFF; /* - * Set if any of MDS/TAA/MMIO/RFDS are going to enable VERW clearing - * through X86_FEATURE_CLEAR_CPU_BUF on kernel and guest entry. + * Set if any of MDS/TAA/MMIO/RFDS are going to enable VERW clearing on exit to + * userspace *and* on entry to KVM guests. */ static bool verw_clear_cpu_buf_mitigation_selected __ro_after_init; @@ -536,6 +536,7 @@ static void __init mds_apply_mitigation(void) if (mds_mitigation == MDS_MITIGATION_FULL || mds_mitigation == MDS_MITIGATION_VMWERV) { setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); + setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM); if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) && (mds_nosmt || smt_mitigations == SMT_MITIGATIONS_ON)) cpu_smt_disable(false); @@ -647,6 +648,7 @@ static void __init taa_apply_mitigation(void) * present on host, enable the mitigation for UCODE_NEEDED as well. */ setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); + setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM); if (taa_nosmt || smt_mitigations == SMT_MITIGATIONS_ON) cpu_smt_disable(false); @@ -748,6 +750,7 @@ static void __init mmio_apply_mitigation(void) */ if (verw_clear_cpu_buf_mitigation_selected) { setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); + setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM); static_branch_disable(&cpu_buf_vm_clear); } else { static_branch_enable(&cpu_buf_vm_clear); @@ -839,8 +842,10 @@ static void __init rfds_update_mitigation(void) static void __init rfds_apply_mitigation(void) { - if (rfds_mitigation == RFDS_MITIGATION_VERW) + if (rfds_mitigation == RFDS_MITIGATION_VERW) { setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF); + setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM); + } } static __init int rfds_parse_cmdline(char *str) diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index 93cf2ca7919a..7e7bb9b7162f 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -165,7 +165,7 @@ SYM_FUNC_START(__vmx_vcpu_run) mov VCPU_RAX(%_ASM_AX), %_ASM_AX /* Clobbers EFLAGS.ZF */ - CLEAR_CPU_BUFFERS + VM_CLEAR_CPU_BUFFERS /* Check @flags to see if vmlaunch or vmresume is needed. */ testl $VMX_RUN_VMRESUME, WORD_SIZE(%_ASM_SP) -- 2.52.0.rc1.455.g30608eb744-goog