From 5e17c624010a82bbcca9b955155781927eb6532a Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 4 May 2021 10:17:30 -0700 Subject: KVM: VMX: Disable loading of TSX_CTRL MSR the more conventional way Tag TSX_CTRL as not needing to be loaded when RTM isn't supported in the host. Crushing the write mask to '0' has the same effect, but requires more mental gymnastics to understand. Signed-off-by: Sean Christopherson Message-Id: <20210504171734.1434054-12-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) (limited to 'arch/x86/kvm/vmx/vmx.c') diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 39506704be96..bd2187b4cc53 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1771,7 +1771,13 @@ static void setup_msrs(struct vcpu_vmx *vmx) guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDTSCP) || guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDPID)); - vmx_setup_uret_msr(vmx, MSR_IA32_TSX_CTRL, true); + /* + * hle=0, rtm=0, tsx_ctrl=1 can be found with some combinations of new + * kernel and old userspace. If those guests run on a tsx=off host, do + * allow guests to use TSX_CTRL, but don't change the value in hardware + * so that TSX remains always disabled. + */ + vmx_setup_uret_msr(vmx, MSR_IA32_TSX_CTRL, boot_cpu_has(X86_FEATURE_RTM)); if (cpu_has_vmx_msr_bitmap()) vmx_update_msr_bitmap(&vmx->vcpu); @@ -6919,23 +6925,15 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu) vmx->guest_uret_msrs[i].data = 0; vmx->guest_uret_msrs[i].mask = -1ull; } - tsx_ctrl = vmx_find_uret_msr(vmx, MSR_IA32_TSX_CTRL); - if (tsx_ctrl) { + if (boot_cpu_has(X86_FEATURE_RTM)) { /* * TSX_CTRL_CPUID_CLEAR is handled in the CPUID interception. * Keep the host value unchanged to avoid changing CPUID bits * under the host kernel's feet. - * - * hle=0, rtm=0, tsx_ctrl=1 can be found with some combinations - * of new kernel and old userspace. If those guests run on a - * tsx=off host, do allow guests to use TSX_CTRL, but do not - * change the value on the host so that TSX remains always - * disabled. */ - if (boot_cpu_has(X86_FEATURE_RTM)) + tsx_ctrl = vmx_find_uret_msr(vmx, MSR_IA32_TSX_CTRL); + if (tsx_ctrl) vmx->guest_uret_msrs[i].mask = ~(u64)TSX_CTRL_CPUID_CLEAR; - else - vmx->guest_uret_msrs[i].mask = 0; } err = alloc_loaded_vmcs(&vmx->vmcs01); -- cgit v1.2.3