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(-) -- 2.26.0
