KVM: x86: Don't update vcpu->arch.pv_eoi.msr_val when a bogus value was written to...

When kvm_gfn_to_hva_cache_init() call from kvm_lapic_set_pv_eoi() fails,
MSR write to MSR_KVM_PV_EOI_EN results in #GP so it is reasonable to
expect that the value we keep internally in KVM wasn't updated.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20211108152819.12485-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 3573b50d9036a141c255e1a4eaae8cda74a0ef39..4388d22df5002928e69b40d3210878180963d00c 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2857,20 +2857,25 @@ int kvm_lapic_set_pv_eoi(struct kvm_vcpu *vcpu, u64 data, unsigned long len)
        u64 addr = data & ~KVM_MSR_ENABLED;
        struct gfn_to_hva_cache *ghc = &vcpu->arch.pv_eoi.data;
        unsigned long new_len;
+       int ret;
 
        if (!IS_ALIGNED(addr, 4))
                return 1;
 
-       vcpu->arch.pv_eoi.msr_val = data;
-       if (!pv_eoi_enabled(vcpu))
-               return 0;
+       if (data & KVM_MSR_ENABLED) {
+               if (addr == ghc->gpa && len <= ghc->len)
+                       new_len = ghc->len;
+               else
+                       new_len = len;
 
-       if (addr == ghc->gpa && len <= ghc->len)
-               new_len = ghc->len;
-       else
-               new_len = len;
+               ret = kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, addr, new_len);
+               if (ret)
+                       return ret;
+       }
+
+       vcpu->arch.pv_eoi.msr_val = data;
 
-       return kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, addr, new_len);
+       return 0;
 }
 
 int kvm_apic_accept_events(struct kvm_vcpu *vcpu)