KVM: x86: Add support for RDPID without RDTSCP

commit 36fa06f9ff39f23e03cd8206dc6bbb7711c23be6 upstream.

Allow userspace to enable RDPID for a guest without also enabling RDTSCP.
Aside from checking for RDPID support in the obvious flows, VMX also needs
to set ENABLE_RDTSCP=1 when RDPID is exposed.

For the record, there is no known scenario where enabling RDPID without
RDTSCP is desirable.  But, both AMD and Intel architectures allow for the
condition, i.e. this is purely to make KVM more architecturally accurate.

Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
Cc: stable@vger.kernel.org
Reported-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 5364458cf60ba2716646652f71316ed2b95a8a0c..48ee3deab64b1c5b12737c947ae3d1744ac0a1f7 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2741,7 +2741,8 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                if (!boot_cpu_has(X86_FEATURE_RDTSCP))
                        return 1;
                if (!msr_info->host_initiated &&
-                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
                        return 1;
                msr_info->data = svm->tsc_aux;
                break;
@@ -2952,7 +2953,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
                        return 1;
 
                if (!msr->host_initiated &&
-                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
                        return 1;
 
                /*

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2246f52ac6ed6ed906f32162e75578d4db6f3299..82d184c94eda4660f19218fdfd7d0af08dbaad3a 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1734,7 +1734,8 @@ static void setup_msrs(struct vcpu_vmx *vmx)
        if (update_transition_efer(vmx))
                vmx_setup_uret_msr(vmx, MSR_EFER);
 
-       if (guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDTSCP))
+       if (guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDTSCP)  ||
+           guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDPID))
                vmx_setup_uret_msr(vmx, MSR_TSC_AUX);
 
        vmx_setup_uret_msr(vmx, MSR_IA32_TSX_CTRL);
@@ -1933,7 +1934,8 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                break;
        case MSR_TSC_AUX:
                if (!msr_info->host_initiated &&
-                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
                        return 1;
                goto find_uret_msr;
        case MSR_IA32_DEBUGCTLMSR:
@@ -2230,7 +2232,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                break;
        case MSR_TSC_AUX:
                if (!msr_info->host_initiated &&
-                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
+                   !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
                        return 1;
                /* Check reserved bit, higher 32 bits should be zero */
                if ((data >> 32) != 0)
@@ -4302,7 +4305,23 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
                                                  xsaves_enabled, false);
        }
 
-       vmx_adjust_sec_exec_feature(vmx, &exec_control, rdtscp, RDTSCP);
+       /*
+        * RDPID is also gated by ENABLE_RDTSCP, turn on the control if either
+        * feature is exposed to the guest.  This creates a virtualization hole
+        * if both are supported in hardware but only one is exposed to the
+        * guest, but letting the guest execute RDTSCP or RDPID when either one
+        * is advertised is preferable to emulating the advertised instruction
+        * in KVM on #UD, and obviously better than incorrectly injecting #UD.
+        */
+       if (cpu_has_vmx_rdtscp()) {
+               bool rdpid_or_rdtscp_enabled =
+                       guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) ||
+                       guest_cpuid_has(vcpu, X86_FEATURE_RDPID);
+
+               vmx_adjust_secondary_exec_control(vmx, &exec_control,
+                                                 SECONDARY_EXEC_ENABLE_RDTSCP,
+                                                 rdpid_or_rdtscp_enabled, false);
+       }
        vmx_adjust_sec_exec_feature(vmx, &exec_control, invpcid, INVPCID);
 
        vmx_adjust_sec_exec_exiting(vmx, &exec_control, rdrand, RDRAND);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c37c23c6b17885819e2abe236d16b2b9ed89d281..947a13557c3ea0d78a0e30ab23e10620af7c372b 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5864,7 +5864,8 @@ static void kvm_init_msr_list(void)
                                continue;
                        break;
                case MSR_TSC_AUX:
-                       if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
+                       if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP) &&
+                           !kvm_cpu_cap_has(X86_FEATURE_RDPID))
                                continue;
                        break;
                case MSR_IA32_UMWAIT_CONTROL: