From: Sean Christopherson seanjc@google.com
[ Upstream commit 8a4351ac302cd8c19729ba2636acfd0467c22ae8 ]
Move VMX's logic to check DEBUGCTL values into a standalone helper so that the code can be used by nested VM-Enter to apply the same logic to the value being loaded from vmcs12.
KVM needs to explicitly check vmcs12->guest_ia32_debugctl on nested VM-Enter, as hardware may support features that KVM does not, i.e. relying on hardware to detect invalid guest state will result in false negatives. Unfortunately, that means applying KVM's funky suppression of BTF and LBR to vmcs12 so as not to break existing guests.
No functional change intended.
Reviewed-by: Dapeng Mi dapeng1.mi@linux.intel.com Link: https://lore.kernel.org/r/20250610232010.162191-6-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com Stable-dep-of: 095686e6fcb4 ("KVM: nVMX: Check vmcs12->guest_ia32_debugctl on nested VM-Enter") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/vmx/vmx.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index eec0aa13e002..e812e98b06a8 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -2195,6 +2195,19 @@ static u64 vmx_get_supported_debugctl(struct kvm_vcpu *vcpu, bool host_initiated return debugctl; }
+static bool vmx_is_valid_debugctl(struct kvm_vcpu *vcpu, u64 data, + bool host_initiated) +{ + u64 invalid; + + invalid = data & ~vmx_get_supported_debugctl(vcpu, host_initiated); + if (invalid & (DEBUGCTLMSR_BTF | DEBUGCTLMSR_LBR)) { + kvm_pr_unimpl_wrmsr(vcpu, MSR_IA32_DEBUGCTLMSR, data); + invalid &= ~(DEBUGCTLMSR_BTF | DEBUGCTLMSR_LBR); + } + return !invalid; +} + /* * Writes msr value into the appropriate "register". * Returns 0 on success, non-0 otherwise. @@ -2263,19 +2276,12 @@ int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) } vmcs_writel(GUEST_SYSENTER_ESP, data); break; - case MSR_IA32_DEBUGCTLMSR: { - u64 invalid; - - invalid = data & ~vmx_get_supported_debugctl(vcpu, msr_info->host_initiated); - if (invalid & (DEBUGCTLMSR_BTF|DEBUGCTLMSR_LBR)) { - kvm_pr_unimpl_wrmsr(vcpu, msr_index, data); - data &= ~(DEBUGCTLMSR_BTF|DEBUGCTLMSR_LBR); - invalid &= ~(DEBUGCTLMSR_BTF|DEBUGCTLMSR_LBR); - } - - if (invalid) + case MSR_IA32_DEBUGCTLMSR: + if (!vmx_is_valid_debugctl(vcpu, data, msr_info->host_initiated)) return 1;
+ data &= vmx_get_supported_debugctl(vcpu, msr_info->host_initiated); + if (is_guest_mode(vcpu) && get_vmcs12(vcpu)->vm_exit_controls & VM_EXIT_SAVE_DEBUG_CONTROLS) get_vmcs12(vcpu)->guest_ia32_debugctl = data; @@ -2285,7 +2291,6 @@ int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) (data & DEBUGCTLMSR_LBR)) intel_pmu_create_guest_lbr_event(vcpu); return 0; - } case MSR_IA32_BNDCFGS: if (!kvm_mpx_supported() || (!msr_info->host_initiated &&