2019-08-27 16:05:30

by Vitaly Kuznetsov

Subject: [PATCH 1/3] KVM: x86: hyper-v: don't crash on KVM_GET_SUPPORTED_HV_CPUID when kvm_intel.nested is disabled

If kvm_intel is loaded with nested=0 parameter an attempt to perform
KVM_GET_SUPPORTED_HV_CPUID results in OOPS as nested_get_evmcs_version hook
in kvm_x86_ops is NULL (we assign it in nested_vmx_hardware_setup() and
this only happens in case nested is enabled).

Check that kvm_x86_ops->nested_get_evmcs_version is not NULL before
calling it. With this, we can remove the stub from svm as it is no
longer needed.

Fixes: e2e871ab2f02 ("x86/kvm/hyper-v: Introduce nested_get_evmcs_version() helper")
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
arch/x86/kvm/hyperv.c | 5 ++++-
arch/x86/kvm/svm.c | 8 +-------
arch/x86/kvm/vmx/vmx.c | 1 +
3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 58bf61b17431..3f5ad84853fb 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1785,7 +1785,7 @@ 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)
{
- uint16_t evmcs_ver = kvm_x86_ops->nested_get_evmcs_version(vcpu);
+ uint16_t evmcs_ver = 0;
struct kvm_cpuid_entry2 cpuid_entries[] = {
{ .function = HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS },
{ .function = HYPERV_CPUID_INTERFACE },
@@ -1797,6 +1797,9 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
};
int i, nent = ARRAY_SIZE(cpuid_entries);

+ if (kvm_x86_ops->nested_get_evmcs_version)
+ evmcs_ver = kvm_x86_ops->nested_get_evmcs_version(vcpu);
+
/* Skip NESTED_FEATURES if eVMCS is not supported */
if (!evmcs_ver)
--nent;
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 572c7c4ca974..40175c42f116 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7122,12 +7122,6 @@ static int svm_unregister_enc_region(struct kvm *kvm,
return ret;
}

-static uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
-{
- /* Not supported */
- return 0;
-}
-
static int nested_enable_evmcs(struct kvm_vcpu *vcpu,
uint16_t *vmcs_version)
{
@@ -7344,7 +7338,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
.mem_enc_unreg_region = svm_unregister_enc_region,

.nested_enable_evmcs = nested_enable_evmcs,
- .nested_get_evmcs_version = nested_get_evmcs_version,
+ .nested_get_evmcs_version = NULL,

.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 3c936e7366b9..c81e5210b159 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7812,6 +7812,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
.set_nested_state = NULL,
.get_vmcs12_pages = NULL,
.nested_enable_evmcs = NULL,
+ .nested_get_evmcs_version = NULL,
.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
.apic_init_signal_blocked = vmx_apic_init_signal_blocked,
};
--
2.20.1

2019-08-27 17:12:36

by Jim Mattson

Subject: Re: [PATCH 1/3] KVM: x86: hyper-v: don't crash on KVM_GET_SUPPORTED_HV_CPUID when kvm_intel.nested is disabled

On Tue, Aug 27, 2019 at 9:04 AM Vitaly Kuznetsov <[email protected]> wrote:
>
> If kvm_intel is loaded with nested=0 parameter an attempt to perform
> KVM_GET_SUPPORTED_HV_CPUID results in OOPS as nested_get_evmcs_version hook
> in kvm_x86_ops is NULL (we assign it in nested_vmx_hardware_setup() and
> this only happens in case nested is enabled).
>
> Check that kvm_x86_ops->nested_get_evmcs_version is not NULL before
> calling it. With this, we can remove the stub from svm as it is no
> longer needed.
>
> Fixes: e2e871ab2f02 ("x86/kvm/hyper-v: Introduce nested_get_evmcs_version() helper")
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
Reviewed-by: Jim Mattson <[email protected]>

2019-08-27 18:55:21

by Radim Krčmář

Subject: Re: [PATCH 1/3] KVM: x86: hyper-v: don't crash on KVM_GET_SUPPORTED_HV_CPUID when kvm_intel.nested is disabled

2019-08-27 18:04+0200, Vitaly Kuznetsov:
> If kvm_intel is loaded with nested=0 parameter an attempt to perform
> KVM_GET_SUPPORTED_HV_CPUID results in OOPS as nested_get_evmcs_version hook
> in kvm_x86_ops is NULL (we assign it in nested_vmx_hardware_setup() and
> this only happens in case nested is enabled).
>
> Check that kvm_x86_ops->nested_get_evmcs_version is not NULL before
> calling it. With this, we can remove the stub from svm as it is no
> longer needed.
>

Added

Cc: <[email protected]>

> Fixes: e2e871ab2f02 ("x86/kvm/hyper-v: Introduce nested_get_evmcs_version() helper")
> Signed-off-by: Vitaly Kuznetsov <[email protected]>

and applied, thanks.