KVM: x86: Add a framework for supporting MSR-based features
commit 801e459a6f3a63af9d447e6249088c76ae16efc4 upstream
Provide a new KVM capability that allows bits within MSRs to be recognized
as features. Two new ioctls are added to the /dev/kvm ioctl routine to
retrieve the list of these MSRs and then retrieve their values. A kvm_x86_ops
callback is used to determine support for the listed MSR-based features.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[Tweaked documentation. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index e46c14f..3ff58a8 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -122,14 +122,15 @@
privileged user (CAP_SYS_ADMIN).
-4.3 KVM_GET_MSR_INDEX_LIST
+4.3 KVM_GET_MSR_INDEX_LIST, KVM_GET_MSR_FEATURE_INDEX_LIST
-Capability: basic
+Capability: basic, KVM_CAP_GET_MSR_FEATURES for KVM_GET_MSR_FEATURE_INDEX_LIST
Architectures: x86
-Type: system
+Type: system ioctl
Parameters: struct kvm_msr_list (in/out)
Returns: 0 on success; -1 on error
Errors:
+ EFAULT: the msr index list cannot be read from or written to
E2BIG: the msr index list is to be to fit in the array specified by
the user.
@@ -138,16 +139,23 @@
__u32 indices[0];
};
-This ioctl returns the guest msrs that are supported. The list varies
-by kvm version and host processor, but does not change otherwise. The
-user fills in the size of the indices array in nmsrs, and in return
-kvm adjusts nmsrs to reflect the actual number of msrs and fills in
-the indices array with their numbers.
+The user fills in the size of the indices array in nmsrs, and in return
+kvm adjusts nmsrs to reflect the actual number of msrs and fills in the
+indices array with their numbers.
+
+KVM_GET_MSR_INDEX_LIST returns the guest msrs that are supported. The list
+varies by kvm version and host processor, but does not change otherwise.
Note: if kvm indicates supports MCE (KVM_CAP_MCE), then the MCE bank MSRs are
not returned in the MSR list, as different vcpus can have a different number
of banks, as set via the KVM_X86_SETUP_MCE ioctl.
+KVM_GET_MSR_FEATURE_INDEX_LIST returns the list of MSRs that can be passed
+to the KVM_GET_MSRS system ioctl. This lets userspace probe host capabilities
+and processor features that are exposed via MSRs (e.g., VMX capabilities).
+This list also varies by kvm version and host processor, but does not change
+otherwise.
+
4.4 KVM_CHECK_EXTENSION
@@ -474,14 +482,22 @@
4.18 KVM_GET_MSRS
-Capability: basic
+Capability: basic (vcpu), KVM_CAP_GET_MSR_FEATURES (system)
Architectures: x86
-Type: vcpu ioctl
+Type: system ioctl, vcpu ioctl
Parameters: struct kvm_msrs (in/out)
-Returns: 0 on success, -1 on error
+Returns: number of msrs successfully returned;
+ -1 on error
+When used as a system ioctl:
+Reads the values of MSR-based features that are available for the VM. This
+is similar to KVM_GET_SUPPORTED_CPUID, but it returns MSR indices and values.
+The list of msr-based features can be obtained using KVM_GET_MSR_FEATURE_INDEX_LIST
+in a system ioctl.
+
+When used as a vcpu ioctl:
Reads model-specific registers from the vcpu. Supported msr indices can
-be obtained using KVM_GET_MSR_INDEX_LIST.
+be obtained using KVM_GET_MSR_INDEX_LIST in a system ioctl.
struct kvm_msrs {
__u32 nmsrs; /* number of msrs in entries */
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ce6a70a..16d588c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1025,6 +1025,8 @@
void (*cancel_hv_timer)(struct kvm_vcpu *vcpu);
void (*setup_mce)(struct kvm_vcpu *vcpu);
+
+ int (*get_msr_feature)(struct kvm_msr_entry *entry);
};
struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index c8ae426..16f3e26 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3485,6 +3485,11 @@
return 0;
}
+static int svm_get_msr_feature(struct kvm_msr_entry *msr)
+{
+ return 1;
+}
+
static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
{
struct vcpu_svm *svm = to_svm(vcpu);
@@ -5504,6 +5509,7 @@
.vcpu_unblocking = svm_vcpu_unblocking,
.update_bp_intercept = update_bp_intercept,
+ .get_msr_feature = svm_get_msr_feature,
.get_msr = svm_get_msr,
.set_msr = svm_set_msr,
.get_segment_base = svm_get_segment_base,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0f4c946..3e04e19 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3153,6 +3153,11 @@
return !(val & ~valid_bits);
}
+static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
+{
+ return 1;
+}
+
/*
* Reads an msr value (of 'msr_index') into 'pdata'.
* Returns 0 on success, non-0 otherwise.
@@ -11659,6 +11664,7 @@
.vcpu_put = vmx_vcpu_put,
.update_bp_intercept = update_exception_bitmap,
+ .get_msr_feature = vmx_get_msr_feature,
.get_msr = vmx_get_msr,
.set_msr = vmx_set_msr,
.get_segment_base = vmx_get_segment_base,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cc314e7..6c0bb89 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1008,6 +1008,28 @@
static unsigned num_emulated_msrs;
+/*
+ * List of msr numbers which are used to expose MSR-based features that
+ * can be used by a hypervisor to validate requested CPU features.
+ */
+static u32 msr_based_features[] = {
+};
+
+static unsigned int num_msr_based_features;
+
+static int do_get_msr_feature(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
+{
+ struct kvm_msr_entry msr;
+
+ msr.index = index;
+ if (kvm_x86_ops->get_msr_feature(&msr))
+ return 1;
+
+ *data = msr.data;
+
+ return 0;
+}
+
bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
{
if (efer & efer_reserved_bits)
@@ -2546,13 +2568,11 @@
int (*do_msr)(struct kvm_vcpu *vcpu,
unsigned index, u64 *data))
{
- int i, idx;
+ int i;
- idx = srcu_read_lock(&vcpu->kvm->srcu);
for (i = 0; i < msrs->nmsrs; ++i)
if (do_msr(vcpu, entries[i].index, &entries[i].data))
break;
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
return i;
}
@@ -2652,6 +2672,7 @@
case KVM_CAP_ASSIGN_DEV_IRQ:
case KVM_CAP_PCI_2_3:
#endif
+ case KVM_CAP_GET_MSR_FEATURES:
r = 1;
break;
case KVM_CAP_ADJUST_CLOCK:
@@ -2771,6 +2792,31 @@
goto out;
r = 0;
break;
+ case KVM_GET_MSR_FEATURE_INDEX_LIST: {
+ struct kvm_msr_list __user *user_msr_list = argp;
+ struct kvm_msr_list msr_list;
+ unsigned int n;
+
+ r = -EFAULT;
+ if (copy_from_user(&msr_list, user_msr_list, sizeof(msr_list)))
+ goto out;
+ n = msr_list.nmsrs;
+ msr_list.nmsrs = num_msr_based_features;
+ if (copy_to_user(user_msr_list, &msr_list, sizeof(msr_list)))
+ goto out;
+ r = -E2BIG;
+ if (n < msr_list.nmsrs)
+ goto out;
+ r = -EFAULT;
+ if (copy_to_user(user_msr_list->indices, &msr_based_features,
+ num_msr_based_features * sizeof(u32)))
+ goto out;
+ r = 0;
+ break;
+ }
+ case KVM_GET_MSRS:
+ r = msr_io(NULL, argp, do_get_msr_feature, 1);
+ break;
}
default:
r = -EINVAL;
@@ -3452,12 +3498,18 @@
r = 0;
break;
}
- case KVM_GET_MSRS:
+ case KVM_GET_MSRS: {
+ int idx = srcu_read_lock(&vcpu->kvm->srcu);
r = msr_io(vcpu, argp, do_get_msr, 1);
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
break;
- case KVM_SET_MSRS:
+ }
+ case KVM_SET_MSRS: {
+ int idx = srcu_read_lock(&vcpu->kvm->srcu);
r = msr_io(vcpu, argp, do_set_msr, 0);
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
break;
+ }
case KVM_TPR_ACCESS_REPORTING: {
struct kvm_tpr_access_ctl tac;
@@ -4237,6 +4289,19 @@
j++;
}
num_emulated_msrs = j;
+
+ for (i = j = 0; i < ARRAY_SIZE(msr_based_features); i++) {
+ struct kvm_msr_entry msr;
+
+ msr.index = msr_based_features[i];
+ if (kvm_x86_ops->get_msr_feature(&msr))
+ continue;
+
+ if (j < i)
+ msr_based_features[j] = msr_based_features[i];
+ j++;
+ }
+ num_msr_based_features = j;
}
static int vcpu_mmio_write(struct kvm_vcpu *vcpu, gpa_t addr, int len,
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 05b9bb6..a0a365c 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -717,6 +717,7 @@
#define KVM_TRACE_PAUSE __KVM_DEPRECATED_MAIN_0x07
#define KVM_TRACE_DISABLE __KVM_DEPRECATED_MAIN_0x08
#define KVM_GET_EMULATED_CPUID _IOWR(KVMIO, 0x09, struct kvm_cpuid2)
+#define KVM_GET_MSR_FEATURE_INDEX_LIST _IOWR(KVMIO, 0x0a, struct kvm_msr_list)
/*
* Extension capability list.
@@ -871,6 +872,7 @@
#define KVM_CAP_MSI_DEVID 131
#define KVM_CAP_PPC_HTM 132
#define KVM_CAP_S390_BPB 152
+#define KVM_CAP_GET_MSR_FEATURES 153
#ifdef KVM_CAP_IRQ_ROUTING