On Tue, Apr 28, 2020 at 4:10 PM Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > > Patch 1 is a "fix" for handling SYSENTER_EIP/ESP in L2 on a 32-bit vCPU. > The primary motivation is to provide consistent behavior after patch 2. > > Patch 2 is essentially a re-submission of a nested VMX optimization to > avoid redundant VMREADs to the SYSENTER fields in the nested VM-Exit path. > > After patch 2 and without patch 1, KVM would end up with weird behavior > where L1 and L2 would only see 32-bit values for their own SYSENTER_E*P > MSRs, but L1 could see a 64-bit value for L2's MSRs. > > Sean Christopherson (2): > KVM: nVMX: Truncate writes to vmcs.SYSENTER_EIP/ESP for 32-bit vCPU > KVM: nVMX: Drop superfluous VMREAD of vmcs02.GUEST_SYSENTER_* > > arch/x86/kvm/vmx/nested.c | 4 ---- > arch/x86/kvm/vmx/vmx.c | 18 ++++++++++++++++-- > 2 files changed, 16 insertions(+), 6 deletions(-) It seems like this could be fixed more generally by truncating natural-width fields on 32-bit vCPUs in handle_vmwrite(). However, that also would imply that we can't shadow any natural-width fields on a 32-bit vCPU.
