Patch "KVM: x86: Check for existing Hyper-V vCPU in kvm_hv_vcpu_init()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    KVM: x86: Check for existing Hyper-V vCPU in kvm_hv_vcpu_init()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-x86-check-for-existing-hyper-v-vcpu-in-kvm_hv_vc.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1bd4e2dd2308823eb419528af6ff7ef407a9fcd5
Author: Sean Christopherson <seanjc@xxxxxxxxxx>
Date:   Tue Aug 30 15:37:08 2022 +0200

    KVM: x86: Check for existing Hyper-V vCPU in kvm_hv_vcpu_init()
    
    [ Upstream commit 1cac8d9f6bd25df3713103e44e2d9ca0c2e03c33 ]
    
    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 <seanjc@xxxxxxxxxx>
    Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
    Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
    Reviewed-by: Wei Liu <wei.liu@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20220830133737.1539624-5-vkuznets@xxxxxxxxxx
    Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Stable-dep-of: 3be29eb7b525 ("KVM: x86: Report error when setting CPUID if Hyper-V allocation fails")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 762b43f0d919..fccc2abddd75 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -929,9 +929,12 @@ 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;
@@ -955,11 +958,9 @@ 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);
 
@@ -1677,10 +1678,8 @@ 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;
@@ -1700,10 +1699,8 @@ 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;
@@ -1992,7 +1989,7 @@ 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);