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KVM: SVM: Move GHCB unmapping to fix RCU warning 

When an SEV-ES guest is running, the GHCB is unmapped as part of the
vCPU run support. However, kvm_vcpu_unmap() triggers an RCU dereference
warning with CONFIG_PROVE_LOCKING=y because the SRCU lock is released
before invoking the vCPU run support.

Move the GHCB unmapping into the prepare_guest_switch callback, which is
invoked while still holding the SRCU lock, eliminating the RCU dereference
warning.

Fixes: 291bd20d5d ("KVM: SVM: Add initial support for a VMGEXIT VMEXIT")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <b2f9b79d15166f2c3e4375c0d9bc3268b7696455.1620332081.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Tom Lendacky 2021-05-06 15:14:41 -05:00 committed by Paolo Bonzini
parent 368340a3c7
commit ce7ea0cfdc
3 changed files with 5 additions and 4 deletions
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5
arch/x86/kvm/svm/sev.c
View File

@ -2197,7 +2197,7 @@ vmgexit_err:
return -EINVAL;
}
static void pre_sev_es_run(struct vcpu_svm *svm)
void sev_es_unmap_ghcb(struct vcpu_svm *svm)
{
if (!svm->ghcb)
return;
@ -2233,9 +2233,6 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu)
struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
int asid = sev_get_asid(svm->vcpu.kvm);
/* Perform any SEV-ES pre-run actions */
pre_sev_es_run(svm);
/* Assign the asid allocated with this SEV guest */
svm->asid = asid;

3
arch/x86/kvm/svm/svm.c
View File

@ -1437,6 +1437,9 @@ static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu)
struct vcpu_svm *svm = to_svm(vcpu);
struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
if (sev_es_guest(vcpu->kvm))
sev_es_unmap_ghcb(svm);
if (svm->guest_state_loaded)
return;

1
arch/x86/kvm/svm/svm.h
View File

@ -581,6 +581,7 @@ void sev_es_init_vmcb(struct vcpu_svm *svm);
void sev_es_create_vcpu(struct vcpu_svm *svm);
void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu);
void sev_es_unmap_ghcb(struct vcpu_svm *svm);
/* vmenter.S */