x86/kvm/lapic: preserve gfn_to_hva_cache len on cache reinit
[ Upstream commit a7c42bb6da6b1b54b2e7bd567636d72d87b10a79 ] 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: NVitaly Kuznetsov <vkuznets@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com> Signed-off-by: NSasha Levin <sashal@kernel.org>
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