This series stems from Lai's RFC patches to intercept LA57 and let the guest own FSGSBASE[*]. Discussion and inspection revealed that KVM does not handle the case where LA57 is supported in hardware but not exposed to the guest. This is actually true for all CR4 bits, but LA57 is currently the only bit that can be reserved and also owned by the guest. I have a unit test for this that I'll post separately. Intercepting LA57 was by far the easiest fix for the immedidate bug, and is likely the right change in the long term as there's no justification for letting the guest own LA57. The middle three patches adjust VMX's CR4 guest/host mask to intercept reserved bits. This required reworking CPUID updates to also refresh said mask at the correct time. The last past is Lai's, which let's the guest own FSGSBASE. This depends on the reserved bit handling being in place. Ran everything through unit tests, and ran the kernel's FSGSBASE selftests in a VM. [*] https://lkml.kernel.org/r/20200928083047.3349-1-jiangshanlai@xxxxxxxxx Lai Jiangshan (2): KVM: x86: Intercept LA57 to inject #GP fault when it's reserved KVM: x86: Let the guest own CR4.FSGSBASE Sean Christopherson (3): KVM: x86: Invoke vendor's vcpu_after_set_cpuid() after all common updates KVM: x86: Move call to update_exception_bitmap() into VMX code KVM: VMX: Intercept guest reserved CR4 bits to inject #GP fault arch/x86/kvm/cpuid.c | 6 +++--- arch/x86/kvm/kvm_cache_regs.h | 2 +- arch/x86/kvm/vmx/vmx.c | 18 +++++++++++++----- 3 files changed, 17 insertions(+), 9 deletions(-) -- 2.28.0
