[PATCH v3 0/2] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful

[PATCH v3 0/2] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful

[Vitaly Kuznetsov]

Changes since v2:
- Keep vCPU version of the ioctl intact but make it 'deprecated' in
  api.rst [Paolo Bonzini]
- First two patches of v2 series already made it to kvm/queue

QEMU series using the feature:
https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg02017.html

Original description:

KVM_GET_SUPPORTED_HV_CPUID was initially implemented as a vCPU ioctl but
this is not very useful when VMM is just trying to query which Hyper-V
features are supported by the host prior to creating VM/vCPUs. The data
in KVM_GET_SUPPORTED_HV_CPUID is mostly static with a few exceptions but
it seems we can change this. Add support for KVM_GET_SUPPORTED_HV_CPUID as
a system ioctl as well.

QEMU specific description:
In some cases QEMU needs to collect the information about which Hyper-V
features are supported by KVM and pass it up the stack. For non-hyper-v
features this is done with system-wide KVM_GET_SUPPORTED_CPUID/
KVM_GET_MSRS ioctls but Hyper-V specific features don't get in the output
(as Hyper-V CPUIDs intersect with KVM's). In QEMU, CPU feature expansion
happens before any KVM vcpus are created so KVM_GET_SUPPORTED_HV_CPUID
can't be used in its current shape.

Vitaly Kuznetsov (2):
  KVM: x86: hyper-v: allow KVM_GET_SUPPORTED_HV_CPUID as a system ioctl
  KVM: selftests: test KVM_GET_SUPPORTED_HV_CPUID as a system ioctl

 Documentation/virt/kvm/api.rst                | 16 ++--
 arch/x86/kvm/hyperv.c                         |  6 +-
 arch/x86/kvm/hyperv.h                         |  4 +-
 arch/x86/kvm/vmx/evmcs.c                      |  3 +-
 arch/x86/kvm/x86.c                            | 45 ++++++----
 include/uapi/linux/kvm.h                      |  3 +-
 .../testing/selftests/kvm/include/kvm_util.h  |  2 +
 tools/testing/selftests/kvm/lib/kvm_util.c    | 26 ++++++
 .../selftests/kvm/x86_64/hyperv_cpuid.c       | 87 +++++++++++--------
 9 files changed, 123 insertions(+), 69 deletions(-)

-- 
2.25.4

[PATCH v3 1/2] KVM: x86: hyper-v: allow KVM_GET_SUPPORTED_HV_CPUID as a system ioctl

[Vitaly Kuznetsov]

KVM_GET_SUPPORTED_HV_CPUID is a vCPU ioctl but its output is now
independent from vCPU and in some cases VMMs may want to use it as a system
ioctl instead. In particular, QEMU doesn CPU feature expansion before any
vCPU gets created so KVM_GET_SUPPORTED_HV_CPUID can't be used.

Convert KVM_GET_SUPPORTED_HV_CPUID to 'dual' system/vCPU ioctl with the
same meaning.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 Documentation/virt/kvm/api.rst | 16 ++++++++----
 arch/x86/kvm/hyperv.c          |  6 ++---
 arch/x86/kvm/hyperv.h          |  4 +--
 arch/x86/kvm/vmx/evmcs.c       |  3 +--
 arch/x86/kvm/x86.c             | 45 ++++++++++++++++++++--------------
 include/uapi/linux/kvm.h       |  3 ++-
 6 files changed, 46 insertions(+), 31 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 425325ff4434..d79f496875ea 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4455,9 +4455,9 @@ that KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is present.
 4.118 KVM_GET_SUPPORTED_HV_CPUID
 --------------------------------
 
-:Capability: KVM_CAP_HYPERV_CPUID
+:Capability: KVM_CAP_HYPERV_CPUID (vcpu), KVM_CAP_SYS_HYPERV_CPUID (system)
 :Architectures: x86
-:Type: vcpu ioctl
+:Type: system ioctl, vcpu ioctl
 :Parameters: struct kvm_cpuid2 (in/out)
 :Returns: 0 on success, -1 on error
 
@@ -4502,9 +4502,6 @@ Currently, the following list of CPUID leaves are returned:
  - HYPERV_CPUID_SYNDBG_INTERFACE
  - HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES
 
-HYPERV_CPUID_NESTED_FEATURES leaf is only exposed when Enlightened VMCS was
-enabled on the corresponding vCPU (KVM_CAP_HYPERV_ENLIGHTENED_VMCS).
-
 Userspace invokes KVM_GET_SUPPORTED_HV_CPUID by passing a kvm_cpuid2 structure
 with the 'nent' field indicating the number of entries in the variable-size
 array 'entries'.  If the number of entries is too low to describe all Hyper-V
@@ -4515,6 +4512,15 @@ number of valid entries in the 'entries' array, which is then filled.
 'index' and 'flags' fields in 'struct kvm_cpuid_entry2' are currently reserved,
 userspace should not expect to get any particular value there.
 
+Note, vcpu version of KVM_GET_SUPPORTED_HV_CPUID is currently deprecated. Unlike
+system ioctl which exposes all supported feature bits unconditionally, vcpu
+version has the following quirks:
+- HYPERV_CPUID_NESTED_FEATURES leaf and HV_X64_ENLIGHTENED_VMCS_RECOMMENDED
+  feature bit are only exposed when Enlightened VMCS was previously enabled
+  on the corresponding vCPU (KVM_CAP_HYPERV_ENLIGHTENED_VMCS).
+- HV_STIMER_DIRECT_MODE_AVAILABLE bit is only exposed with in-kernel LAPIC.
+  (presumes KVM_CREATE_IRQCHIP has already been called).
+
 4.119 KVM_ARM_VCPU_FINALIZE
 ---------------------------
 
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 67a4f60a89b5..532aa259e7a3 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1951,8 +1951,8 @@ int kvm_vm_ioctl_hv_eventfd(struct kvm *kvm, struct kvm_hyperv_eventfd *args)
 	return kvm_hv_eventfd_assign(kvm, args->conn_id, args->fd);
 }
 
-int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
-				struct kvm_cpuid_entry2 __user *entries)
+int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
+		     struct kvm_cpuid_entry2 __user *entries)
 {
 	uint16_t evmcs_ver = 0;
 	struct kvm_cpuid_entry2 cpuid_entries[] = {
@@ -2037,7 +2037,7 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 			 * Direct Synthetic timers only make sense with in-kernel
 			 * LAPIC
 			 */
-			if (lapic_in_kernel(vcpu))
+			if (!vcpu || lapic_in_kernel(vcpu))
 				ent->edx |= HV_STIMER_DIRECT_MODE_AVAILABLE;
 
 			break;
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index e68c6c2e9649..6d7def2b0aad 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -126,7 +126,7 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm,
 void kvm_hv_init_vm(struct kvm *kvm);
 void kvm_hv_destroy_vm(struct kvm *kvm);
 int kvm_vm_ioctl_hv_eventfd(struct kvm *kvm, struct kvm_hyperv_eventfd *args);
-int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
-				struct kvm_cpuid_entry2 __user *entries);
+int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
+		     struct kvm_cpuid_entry2 __user *entries);
 
 #endif
diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index e5325bd0f304..220301577fea 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -327,7 +327,6 @@ bool nested_enlightened_vmentry(struct kvm_vcpu *vcpu, u64 *evmcs_gpa)
 
 uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
 {
-	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	/*
 	 * vmcs_version represents the range of supported Enlightened VMCS
 	 * versions: lower 8 bits is the minimal version, higher 8 bits is the
@@ -335,7 +334,7 @@ uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
 	 * KVM_EVMCS_VERSION.
 	 */
 	if (kvm_cpu_cap_get(X86_FEATURE_VMX) &&
-	    vmx->nested.enlightened_vmcs_enabled)
+	    (!vcpu || to_vmx(vcpu)->nested.enlightened_vmcs_enabled))
 		return (KVM_EVMCS_VERSION << 8) | 1;
 
 	return 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c4015a43cc8a..6e517c023eb1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3591,6 +3591,27 @@ static inline bool kvm_can_mwait_in_guest(void)
 		boot_cpu_has(X86_FEATURE_ARAT);
 }
 
+static int kvm_ioctl_get_supported_hv_cpuid(struct kvm_vcpu *vcpu,
+					    struct kvm_cpuid2 __user *cpuid_arg)
+{
+	struct kvm_cpuid2 cpuid;
+	int r;
+
+	r = -EFAULT;
+	if (copy_from_user(&cpuid, cpuid_arg, sizeof(cpuid)))
+		return r;
+
+	r = kvm_get_hv_cpuid(vcpu, &cpuid, cpuid_arg->entries);
+	if (r)
+		return r;
+
+	r = -EFAULT;
+	if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid)))
+		return r;
+
+	return 0;
+}
+
 int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 {
 	int r = 0;
@@ -3627,6 +3648,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_HYPERV_TLBFLUSH:
 	case KVM_CAP_HYPERV_SEND_IPI:
 	case KVM_CAP_HYPERV_CPUID:
+	case KVM_CAP_SYS_HYPERV_CPUID:
 	case KVM_CAP_PCI_SEGMENT:
 	case KVM_CAP_DEBUGREGS:
 	case KVM_CAP_X86_ROBUST_SINGLESTEP:
@@ -3811,6 +3833,9 @@ long kvm_arch_dev_ioctl(struct file *filp,
 	case KVM_GET_MSRS:
 		r = msr_io(NULL, argp, do_get_msr_feature, 1);
 		break;
+	case KVM_GET_SUPPORTED_HV_CPUID:
+		r = kvm_ioctl_get_supported_hv_cpuid(NULL, argp);
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -4880,25 +4905,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		srcu_read_unlock(&vcpu->kvm->srcu, idx);
 		break;
 	}
-	case KVM_GET_SUPPORTED_HV_CPUID: {
-		struct kvm_cpuid2 __user *cpuid_arg = argp;
-		struct kvm_cpuid2 cpuid;
-
-		r = -EFAULT;
-		if (copy_from_user(&cpuid, cpuid_arg, sizeof(cpuid)))
-			goto out;
-
-		r = kvm_vcpu_ioctl_get_hv_cpuid(vcpu, &cpuid,
-						cpuid_arg->entries);
-		if (r)
-			goto out;
-
-		r = -EFAULT;
-		if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid)))
-			goto out;
-		r = 0;
+	case KVM_GET_SUPPORTED_HV_CPUID:
+		r = kvm_ioctl_get_supported_hv_cpuid(vcpu, argp);
 		break;
-	}
 	default:
 		r = -EINVAL;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 58f43aa1fc21..415eb290bcf7 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1052,6 +1052,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_STEAL_TIME 187
 #define KVM_CAP_X86_USER_SPACE_MSR 188
 #define KVM_CAP_X86_MSR_FILTER 189
+#define KVM_CAP_SYS_HYPERV_CPUID 190
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1510,7 +1511,7 @@ struct kvm_enc_region {
 /* Available with KVM_CAP_MANUAL_DIRTY_LOG_PROTECT_2 */
 #define KVM_CLEAR_DIRTY_LOG          _IOWR(KVMIO, 0xc0, struct kvm_clear_dirty_log)
 
-/* Available with KVM_CAP_HYPERV_CPUID */
+/* Available with KVM_CAP_HYPERV_CPUID (vcpu) / KVM_CAP_SYS_HYPERV_CPUID (system) */
 #define KVM_GET_SUPPORTED_HV_CPUID _IOWR(KVMIO, 0xc1, struct kvm_cpuid2)
 
 /* Available with KVM_CAP_ARM_SVE */
-- 
2.25.4

[PATCH v3 2/2] KVM: selftests: test KVM_GET_SUPPORTED_HV_CPUID as a system ioctl

[Vitaly Kuznetsov]

KVM_GET_SUPPORTED_HV_CPUID is now supported as both vCPU and VM ioctl,
test that.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 .../testing/selftests/kvm/include/kvm_util.h  |  2 +
 tools/testing/selftests/kvm/lib/kvm_util.c    | 26 ++++++
 .../selftests/kvm/x86_64/hyperv_cpuid.c       | 87 +++++++++++--------
 3 files changed, 77 insertions(+), 38 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 919e161dd289..59482e4eb308 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -112,6 +112,8 @@ void vcpu_ioctl(struct kvm_vm *vm, uint32_t vcpuid, unsigned long ioctl,
 int _vcpu_ioctl(struct kvm_vm *vm, uint32_t vcpuid, unsigned long ioctl,
 		void *arg);
 void vm_ioctl(struct kvm_vm *vm, unsigned long ioctl, void *arg);
+void kvm_ioctl(struct kvm_vm *vm, unsigned long ioctl, void *arg);
+int _kvm_ioctl(struct kvm_vm *vm, unsigned long ioctl, void *arg);
 void vm_mem_region_set_flags(struct kvm_vm *vm, uint32_t slot, uint32_t flags);
 void vm_mem_region_move(struct kvm_vm *vm, uint32_t slot, uint64_t new_gpa);
 void vm_mem_region_delete(struct kvm_vm *vm, uint32_t slot);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 74776ee228f2..d49e24a15836 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1518,6 +1518,32 @@ void vm_ioctl(struct kvm_vm *vm, unsigned long cmd, void *arg)
 		cmd, ret, errno, strerror(errno));
 }
 
+/*
+ * KVM system ioctl
+ *
+ * Input Args:
+ *   vm - Virtual Machine
+ *   cmd - Ioctl number
+ *   arg - Argument to pass to the ioctl
+ *
+ * Return: None
+ *
+ * Issues an arbitrary ioctl on a KVM fd.
+ */
+void kvm_ioctl(struct kvm_vm *vm, unsigned long cmd, void *arg)
+{
+	int ret;
+
+	ret = ioctl(vm->kvm_fd, cmd, arg);
+	TEST_ASSERT(ret == 0, "KVM ioctl %lu failed, rc: %i errno: %i (%s)",
+		cmd, ret, errno, strerror(errno));
+}
+
+int _kvm_ioctl(struct kvm_vm *vm, unsigned long cmd, void *arg)
+{
+	return ioctl(vm->kvm_fd, cmd, arg);
+}
+
 /*
  * VM Dump
  *
diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c b/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c
index 745b708c2d3b..88a595b7fbdd 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c
@@ -46,19 +46,19 @@ static bool smt_possible(void)
 }
 
 static void test_hv_cpuid(struct kvm_cpuid2 *hv_cpuid_entries,
-			  bool evmcs_enabled)
+			  bool evmcs_expected)
 {
 	int i;
 	int nent = 9;
 	u32 test_val;
 
-	if (evmcs_enabled)
+	if (evmcs_expected)
 		nent += 1; /* 0x4000000A */
 
 	TEST_ASSERT(hv_cpuid_entries->nent == nent,
 		    "KVM_GET_SUPPORTED_HV_CPUID should return %d entries"
 		    " with evmcs=%d (returned %d)",
-		    nent, evmcs_enabled, hv_cpuid_entries->nent);
+		    nent, evmcs_expected, hv_cpuid_entries->nent);
 
 	for (i = 0; i < hv_cpuid_entries->nent; i++) {
 		struct kvm_cpuid_entry2 *entry = &hv_cpuid_entries->entries[i];
@@ -68,7 +68,7 @@ static void test_hv_cpuid(struct kvm_cpuid2 *hv_cpuid_entries,
 			    "function %x is our of supported range",
 			    entry->function);
 
-		TEST_ASSERT(evmcs_enabled || (entry->function != 0x4000000A),
+		TEST_ASSERT(evmcs_expected || (entry->function != 0x4000000A),
 			    "0x4000000A leaf should not be reported");
 
 		TEST_ASSERT(entry->index == 0,
@@ -87,7 +87,7 @@ static void test_hv_cpuid(struct kvm_cpuid2 *hv_cpuid_entries,
 			TEST_ASSERT(entry->eax == test_val,
 				    "Wrong max leaf report in 0x40000000.EAX: %x"
 				    " (evmcs=%d)",
-				    entry->eax, evmcs_enabled
+				    entry->eax, evmcs_expected
 				);
 			break;
 		case 0x40000004:
@@ -110,20 +110,23 @@ static void test_hv_cpuid(struct kvm_cpuid2 *hv_cpuid_entries,
 
 }
 
-void test_hv_cpuid_e2big(struct kvm_vm *vm)
+void test_hv_cpuid_e2big(struct kvm_vm *vm, bool system)
 {
 	static struct kvm_cpuid2 cpuid = {.nent = 0};
 	int ret;
 
-	ret = _vcpu_ioctl(vm, VCPU_ID, KVM_GET_SUPPORTED_HV_CPUID, &cpuid);
+	if (!system)
+		ret = _vcpu_ioctl(vm, VCPU_ID, KVM_GET_SUPPORTED_HV_CPUID, &cpuid);
+	else
+		ret = _kvm_ioctl(vm, KVM_GET_SUPPORTED_HV_CPUID, &cpuid);
 
 	TEST_ASSERT(ret == -1 && errno == E2BIG,
-		    "KVM_GET_SUPPORTED_HV_CPUID didn't fail with -E2BIG when"
-		    " it should have: %d %d", ret, errno);
+		    "%s KVM_GET_SUPPORTED_HV_CPUID didn't fail with -E2BIG when"
+		    " it should have: %d %d", system ? "KVM" : "vCPU", ret, errno);
 }
 
 
-struct kvm_cpuid2 *kvm_get_supported_hv_cpuid(struct kvm_vm *vm)
+struct kvm_cpuid2 *kvm_get_supported_hv_cpuid(struct kvm_vm *vm, bool system)
 {
 	int nent = 20; /* should be enough */
 	static struct kvm_cpuid2 *cpuid;
@@ -137,7 +140,10 @@ struct kvm_cpuid2 *kvm_get_supported_hv_cpuid(struct kvm_vm *vm)
 
 	cpuid->nent = nent;
 
-	vcpu_ioctl(vm, VCPU_ID, KVM_GET_SUPPORTED_HV_CPUID, cpuid);
+	if (!system)
+		vcpu_ioctl(vm, VCPU_ID, KVM_GET_SUPPORTED_HV_CPUID, cpuid);
+	else
+		kvm_ioctl(vm, KVM_GET_SUPPORTED_HV_CPUID, cpuid);
 
 	return cpuid;
 }
@@ -146,45 +152,50 @@ struct kvm_cpuid2 *kvm_get_supported_hv_cpuid(struct kvm_vm *vm)
 int main(int argc, char *argv[])
 {
 	struct kvm_vm *vm;
-	int rv, stage;
 	struct kvm_cpuid2 *hv_cpuid_entries;
-	bool evmcs_enabled;
 
 	/* Tell stdout not to buffer its content */
 	setbuf(stdout, NULL);
 
-	rv = kvm_check_cap(KVM_CAP_HYPERV_CPUID);
-	if (!rv) {
+	if (!kvm_check_cap(KVM_CAP_HYPERV_CPUID)) {
 		print_skip("KVM_CAP_HYPERV_CPUID not supported");
 		exit(KSFT_SKIP);
 	}
 
-	for (stage = 0; stage < 3; stage++) {
-		evmcs_enabled = false;
+	vm = vm_create_default(VCPU_ID, 0, guest_code);
 
-		vm = vm_create_default(VCPU_ID, 0, guest_code);
-		switch (stage) {
-		case 0:
-			test_hv_cpuid_e2big(vm);
-			continue;
-		case 1:
-			break;
-		case 2:
-			if (!nested_vmx_supported() ||
-			    !kvm_check_cap(KVM_CAP_HYPERV_ENLIGHTENED_VMCS)) {
-				print_skip("Enlightened VMCS is unsupported");
-				continue;
-			}
-			vcpu_enable_evmcs(vm, VCPU_ID);
-			evmcs_enabled = true;
-			break;
-		}
+	/* Test vCPU ioctl version */
+	test_hv_cpuid_e2big(vm, false);
+
+	hv_cpuid_entries = kvm_get_supported_hv_cpuid(vm, false);
+	test_hv_cpuid(hv_cpuid_entries, false);
+	free(hv_cpuid_entries);
 
-		hv_cpuid_entries = kvm_get_supported_hv_cpuid(vm);
-		test_hv_cpuid(hv_cpuid_entries, evmcs_enabled);
-		free(hv_cpuid_entries);
-		kvm_vm_free(vm);
+	if (!nested_vmx_supported() ||
+	    !kvm_check_cap(KVM_CAP_HYPERV_ENLIGHTENED_VMCS)) {
+		print_skip("Enlightened VMCS is unsupported");
+		goto do_sys;
 	}
+	vcpu_enable_evmcs(vm, VCPU_ID);
+	hv_cpuid_entries = kvm_get_supported_hv_cpuid(vm, false);
+	test_hv_cpuid(hv_cpuid_entries, true);
+	free(hv_cpuid_entries);
+
+do_sys:
+	/* Test system ioctl version */
+	if (!kvm_check_cap(KVM_CAP_SYS_HYPERV_CPUID)) {
+		print_skip("KVM_CAP_SYS_HYPERV_CPUID not supported");
+		goto out;
+	}
+
+	test_hv_cpuid_e2big(vm, true);
+
+	hv_cpuid_entries = kvm_get_supported_hv_cpuid(vm, true);
+	test_hv_cpuid(hv_cpuid_entries, nested_vmx_supported());
+	free(hv_cpuid_entries);
+
+out:
+	kvm_vm_free(vm);
 
 	return 0;
 }
-- 
2.25.4

Re: [PATCH v3 0/2] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful

[Vitaly Kuznetsov]

Vitaly Kuznetsov <vkuznets@redhat.com> writes:

> Changes since v2:
> - Keep vCPU version of the ioctl intact but make it 'deprecated' in
>   api.rst [Paolo Bonzini]
> - First two patches of v2 series already made it to kvm/queue
>
> QEMU series using the feature:
> https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg02017.html
>
> Original description:
>
> KVM_GET_SUPPORTED_HV_CPUID was initially implemented as a vCPU ioctl but
> this is not very useful when VMM is just trying to query which Hyper-V
> features are supported by the host prior to creating VM/vCPUs. The data
> in KVM_GET_SUPPORTED_HV_CPUID is mostly static with a few exceptions but
> it seems we can change this. Add support for KVM_GET_SUPPORTED_HV_CPUID as
> a system ioctl as well.
>
> QEMU specific description:
> In some cases QEMU needs to collect the information about which Hyper-V
> features are supported by KVM and pass it up the stack. For non-hyper-v
> features this is done with system-wide KVM_GET_SUPPORTED_CPUID/
> KVM_GET_MSRS ioctls but Hyper-V specific features don't get in the output
> (as Hyper-V CPUIDs intersect with KVM's). In QEMU, CPU feature expansion
> happens before any KVM vcpus are created so KVM_GET_SUPPORTED_HV_CPUID
> can't be used in its current shape.
>
> Vitaly Kuznetsov (2):
>   KVM: x86: hyper-v: allow KVM_GET_SUPPORTED_HV_CPUID as a system ioctl
>   KVM: selftests: test KVM_GET_SUPPORTED_HV_CPUID as a system ioctl
>
>  Documentation/virt/kvm/api.rst                | 16 ++--
>  arch/x86/kvm/hyperv.c                         |  6 +-
>  arch/x86/kvm/hyperv.h                         |  4 +-
>  arch/x86/kvm/vmx/evmcs.c                      |  3 +-
>  arch/x86/kvm/x86.c                            | 45 ++++++----
>  include/uapi/linux/kvm.h                      |  3 +-
>  .../testing/selftests/kvm/include/kvm_util.h  |  2 +
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 26 ++++++
>  .../selftests/kvm/x86_64/hyperv_cpuid.c       | 87 +++++++++++--------
>  9 files changed, 123 insertions(+), 69 deletions(-)

Ping)

Still hoping this can be picked up for 5.10.

the latest QEMU patchset was posted last Friday:
https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg02443.html

-- 
Vitaly

Re: [PATCH v3 0/2] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful

[Paolo Bonzini]

On 29/09/20 17:09, Vitaly Kuznetsov wrote:
> Changes since v2:
> - Keep vCPU version of the ioctl intact but make it 'deprecated' in
>    api.rst [Paolo Bonzini]
> - First two patches of v2 series already made it to kvm/queue
> 
> QEMU series using the feature:
> https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg02017.html
> 
> Original description:
> 
> KVM_GET_SUPPORTED_HV_CPUID was initially implemented as a vCPU ioctl but
> this is not very useful when VMM is just trying to query which Hyper-V
> features are supported by the host prior to creating VM/vCPUs. The data
> in KVM_GET_SUPPORTED_HV_CPUID is mostly static with a few exceptions but
> it seems we can change this. Add support for KVM_GET_SUPPORTED_HV_CPUID as
> a system ioctl as well.
> 
> QEMU specific description:
> In some cases QEMU needs to collect the information about which Hyper-V
> features are supported by KVM and pass it up the stack. For non-hyper-v
> features this is done with system-wide KVM_GET_SUPPORTED_CPUID/
> KVM_GET_MSRS ioctls but Hyper-V specific features don't get in the output
> (as Hyper-V CPUIDs intersect with KVM's). In QEMU, CPU feature expansion
> happens before any KVM vcpus are created so KVM_GET_SUPPORTED_HV_CPUID
> can't be used in its current shape.
> 
> Vitaly Kuznetsov (2):
>    KVM: x86: hyper-v: allow KVM_GET_SUPPORTED_HV_CPUID as a system ioctl
>    KVM: selftests: test KVM_GET_SUPPORTED_HV_CPUID as a system ioctl
> 
>   Documentation/virt/kvm/api.rst                | 16 ++--
>   arch/x86/kvm/hyperv.c                         |  6 +-
>   arch/x86/kvm/hyperv.h                         |  4 +-
>   arch/x86/kvm/vmx/evmcs.c                      |  3 +-
>   arch/x86/kvm/x86.c                            | 45 ++++++----
>   include/uapi/linux/kvm.h                      |  3 +-
>   .../testing/selftests/kvm/include/kvm_util.h  |  2 +
>   tools/testing/selftests/kvm/lib/kvm_util.c    | 26 ++++++
>   .../selftests/kvm/x86_64/hyperv_cpuid.c       | 87 +++++++++++--------
>   9 files changed, 123 insertions(+), 69 deletions(-)
> 

Queued, thanks.

Paolo