From: Tom Lendacky thomas.lendacky@amd.com
stable inclusion from stable-v5.15.94 commit 5122e0e44363e3d837592b78bc04222b9d289868 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6FB6C CVE: CVE-2022-27672
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 6f0f2d5ef895d66a3f2b32dd05189ec34afa5a55 upstream.
By default, KVM/SVM will intercept attempts by the guest to transition out of C0. However, the KVM_CAP_X86_DISABLE_EXITS capability can be used by a VMM to change this behavior. To mitigate the cross-thread return address predictions bug (X86_BUG_SMT_RSB), a VMM must not be allowed to override the default behavior to intercept C0 transitions.
Use a module parameter to control the mitigation on processors that are vulnerable to X86_BUG_SMT_RSB. If the processor is vulnerable to the X86_BUG_SMT_RSB bug and the module parameter is set to mitigate the bug, KVM will not allow the disabling of the HLT, MWAIT and CSTATE exits.
Signed-off-by: Tom Lendacky thomas.lendacky@amd.com Message-Id: 4019348b5e07148eb4d593380a5f6713b93c9a16.1675956146.git.thomas.lendacky@amd.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Guo Mengqi guomengqi3@huawei.com Reviewed-by: Wang Weiyang wangweiyang2@huawei.com Reviewed-by: Weilong Chen chenweilong@huawei.com Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- arch/x86/kvm/x86.c | 43 ++++++++++++++++++++++++++++++++----------- 1 file changed, 32 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 52605740b1da..53ef53d5b414 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -174,6 +174,10 @@ module_param(force_emulation_prefix, bool, S_IRUGO); int __read_mostly pi_inject_timer = -1; module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR);
+/* Enable/disable SMT_RSB bug mitigation */ +bool __read_mostly mitigate_smt_rsb; +module_param(mitigate_smt_rsb, bool, 0444); + /* * Restoring the host value for MSRs that are only consumed when running in * usermode, e.g. SYSCALL MSRs and TSC_AUX, can be deferred until the CPU @@ -3945,10 +3949,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_CLOCK_TSC_STABLE; break; case KVM_CAP_X86_DISABLE_EXITS: - r |= KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_PAUSE | - KVM_X86_DISABLE_EXITS_CSTATE; - if(kvm_can_mwait_in_guest()) - r |= KVM_X86_DISABLE_EXITS_MWAIT; + r = KVM_X86_DISABLE_EXITS_PAUSE; + + if (!mitigate_smt_rsb) { + r |= KVM_X86_DISABLE_EXITS_HLT | + KVM_X86_DISABLE_EXITS_CSTATE; + + if (kvm_can_mwait_in_guest()) + r |= KVM_X86_DISABLE_EXITS_MWAIT; + } break; case KVM_CAP_X86_SMM: /* SMBASE is usually relocated above 1M on modern chipsets, @@ -5491,15 +5500,26 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, if (cap->args[0] & ~KVM_X86_DISABLE_VALID_EXITS) break;
- if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) && - kvm_can_mwait_in_guest()) - kvm->arch.mwait_in_guest = true; - if (cap->args[0] & KVM_X86_DISABLE_EXITS_HLT) - kvm->arch.hlt_in_guest = true; if (cap->args[0] & KVM_X86_DISABLE_EXITS_PAUSE) kvm->arch.pause_in_guest = true; - if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE) - kvm->arch.cstate_in_guest = true; + +#define SMT_RSB_MSG "This processor is affected by the Cross-Thread Return Predictions vulnerability. " \ + "KVM_CAP_X86_DISABLE_EXITS should only be used with SMT disabled or trusted guests." + + if (!mitigate_smt_rsb) { + if (boot_cpu_has_bug(X86_BUG_SMT_RSB) && cpu_smt_possible() && + (cap->args[0] & ~KVM_X86_DISABLE_EXITS_PAUSE)) + pr_warn_once(SMT_RSB_MSG); + + if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) && + kvm_can_mwait_in_guest()) + kvm->arch.mwait_in_guest = true; + if (cap->args[0] & KVM_X86_DISABLE_EXITS_HLT) + kvm->arch.hlt_in_guest = true; + if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE) + kvm->arch.cstate_in_guest = true; + } + r = 0; break; case KVM_CAP_MSR_PLATFORM_INFO: @@ -11698,6 +11718,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_apicv_update_request); static int __init kvm_x86_init(void) { kvm_mmu_x86_module_init(); + mitigate_smt_rsb &= boot_cpu_has_bug(X86_BUG_SMT_RSB) && cpu_smt_possible(); return 0; } module_init(kvm_x86_init);