KVM: SVM: Move GHCB unmapping to fix RCU warning

[ Upstream commit ce7ea0cfdc2e9ff31d12da31c3226deddb9644f5 ]

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: 291bd20d5d88 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index ba56f677cc092804324c53673c9b3a3ecd7fcf37..dbc6214d69def29f3a00e7ebe6f7693ce79282a0 100644 (file)
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1668,7 +1668,7 @@ 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;
@@ -1704,9 +1704,6 @@ 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;
 

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 276d3c728628d6b0f11e141f6968c29e0ad9c3e8..5364458cf60ba2716646652f71316ed2b95a8a0c 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1416,6 +1416,9 @@ static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu)
        struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
        unsigned int i;
 
+       if (sev_es_guest(vcpu->kvm))
+               sev_es_unmap_ghcb(svm);
+
        if (svm->guest_state_loaded)
                return;
 

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 39e071fdab0ca43743014655b39d62df37239a7d..98da0b91f273bcd7ed0250cf9c739d3fcb16db37 100644 (file)
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -571,6 +571,7 @@ 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 */