2022-08-30 13:42:11

by Vitaly Kuznetsov

Subject: [PATCH v6 04/33] KVM: x86: Check for existing Hyper-V vCPU in kvm_hv_vcpu_init()

From: Sean Christopherson <[email protected]>

When potentially allocating/initializing the Hyper-V vCPU struct, check
for an existing instance in kvm_hv_vcpu_init() instead of requiring
callers to perform the check. Relying on callers to do the check is
risky as it's all too easy for KVM to overwrite vcpu->arch.hyperv and
leak memory, and it adds additional burden on callers without much
benefit.

No functional change intended.

Signed-off-by: Sean Christopherson <[email protected]>
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
arch/x86/kvm/hyperv.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 611c349a08bf..8aadd31ed058 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -936,9 +936,12 @@ static void stimer_init(struct kvm_vcpu_hv_stimer *stimer, int timer_index)

static int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)
{
- struct kvm_vcpu_hv *hv_vcpu;
+ struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
int i;

+ if (hv_vcpu)
+ return 0;
+
hv_vcpu = kzalloc(sizeof(struct kvm_vcpu_hv), GFP_KERNEL_ACCOUNT);
if (!hv_vcpu)
return -ENOMEM;
@@ -962,11 +965,9 @@ int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages)
struct kvm_vcpu_hv_synic *synic;
int r;

- if (!to_hv_vcpu(vcpu)) {
- r = kvm_hv_vcpu_init(vcpu);
- if (r)
- return r;
- }
+ r = kvm_hv_vcpu_init(vcpu);
+ if (r)
+ return r;

synic = to_hv_synic(vcpu);

@@ -1660,10 +1661,8 @@ int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
if (!host && !vcpu->arch.hyperv_enabled)
return 1;

- if (!to_hv_vcpu(vcpu)) {
- if (kvm_hv_vcpu_init(vcpu))
- return 1;
- }
+ if (kvm_hv_vcpu_init(vcpu))
+ return 1;

if (kvm_hv_msr_partition_wide(msr)) {
int r;
@@ -1683,10 +1682,8 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
if (!host && !vcpu->arch.hyperv_enabled)
return 1;

- if (!to_hv_vcpu(vcpu)) {
- if (kvm_hv_vcpu_init(vcpu))
- return 1;
- }
+ if (kvm_hv_vcpu_init(vcpu))
+ return 1;

if (kvm_hv_msr_partition_wide(msr)) {
int r;
@@ -2000,7 +1997,7 @@ void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu)
return;
}

- if (!to_hv_vcpu(vcpu) && kvm_hv_vcpu_init(vcpu))
+ if (kvm_hv_vcpu_init(vcpu))
return;

hv_vcpu = to_hv_vcpu(vcpu);
--
2.37.2

2022-09-05 17:17:42

by Wei Liu

Subject: Re: [PATCH v6 04/33] KVM: x86: Check for existing Hyper-V vCPU in kvm_hv_vcpu_init()

On Tue, Aug 30, 2022 at 03:37:08PM +0200, Vitaly Kuznetsov wrote:
> From: Sean Christopherson <[email protected]>
>
> When potentially allocating/initializing the Hyper-V vCPU struct, check
> for an existing instance in kvm_hv_vcpu_init() instead of requiring
> callers to perform the check. Relying on callers to do the check is
> risky as it's all too easy for KVM to overwrite vcpu->arch.hyperv and
> leak memory, and it adds additional burden on callers without much
> benefit.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <[email protected]>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>

Reviewed-by: Wei Liu <[email protected]>