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x86/kvm/lapic: preserve gfn_to_hva_cache len on cache reinit

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vcpu->arch.pv_eoi is accessible through both HV_X64_MSR_VP_ASSIST_PAGE and
MSR_KVM_PV_EOI_EN so on migration userspace may try to restore them in any
order. Values match, however, kvm_lapic_enable_pv_eoi() uses different
length: for Hyper-V case it's the whole struct hv_vp_assist_page, for KVM
native case it is 8. In case we restore KVM-native MSR last cache will
be reinitialized with len=8 so trying to access VP assist page beyond
8 bytes with kvm_read_guest_cached() will fail.

Check if we re-initializing cache for the same address and preserve length
in case it was greater.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2018-10-16 18:50:06 +02:00 • committed by Paolo Bonzini
parent 12e0c6186b
commit a7c42bb6da
1 changed files with 10 additions and 2 deletions
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12
arch/x86/kvm/lapic.c
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@ -2647,14 +2647,22 @@ int kvm_hv_vapic_msr_read(struct kvm_vcpu *vcpu, u32 reg, u64 *data)
int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data, unsigned long len) int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data, unsigned long len)
{ {
u64 addr = data & ~KVM_MSR_ENABLED; u64 addr = data & ~KVM_MSR_ENABLED;
struct gfn_to_hva_cache *ghc = &vcpu->arch.pv_eoi.data;
unsigned long new_len;
if (!IS_ALIGNED(addr, 4)) if (!IS_ALIGNED(addr, 4))
return 1; return 1;
vcpu->arch.pv_eoi.msr_val = data; vcpu->arch.pv_eoi.msr_val = data;
if (!pv_eoi_enabled(vcpu)) if (!pv_eoi_enabled(vcpu))
return 0; return 0;
return kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.pv_eoi.data,
addr, len); if (addr == ghc->gpa && len <= ghc->len)
new_len = ghc->len;
else
new_len = len;
return kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, addr, new_len);
} }
void kvm_apic_accept_events(struct kvm_vcpu *vcpu) void kvm_apic_accept_events(struct kvm_vcpu *vcpu)