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