[PATCH 00/15] KVM: nVMX: Optimize nested VM-Entry

Sean Christopherson
2019-05-07T16:06:45Z

The majority of patches in this series are loosely related optimizations
to pick off low(ish) hanging fruit in nested VM-Entry, e.g. there are
many VMREADs and VMWRITEs that can be optimized away without too much
effort.

The major change (in terms of performance) is to not "put" the vCPU
state when switching between vmcs01 and vmcs02, which can reudce the
latency of a nested VM-Entry by upwards of 1000 cycles.

A few bug fixes are prepended as they touch code that happens to be
modified by the various optimizations.

Sean Christopherson (15):
KVM: nVMX: Don't dump VMCS if virtual APIC page can't be mapped
KVM: VMX: Always signal #GP on WRMSR to MSR_IA32_CR_PAT with bad value
KVM: nVMX: Always sync GUEST_BNDCFGS when it comes from vmcs01
KVM: nVMX: Write ENCLS-exiting bitmap once per vmcs02
KVM: nVMX: Don't rewrite GUEST_PML_INDEX during nested VM-Entry
KVM: nVMX: Don't "put" vCPU or host state when switching VMCS
KVM: nVMX: Don't reread VMCS-agnostic state when switching VMCS
KVM: nVMX: Don't speculatively write virtual-APIC page address
KVM: nVMX: Don't speculatively write APIC-access page address
KVM: nVMX: Update vmcs12 for MSR_IA32_CR_PAT when it's written
KVM: nVMX: Update vmcs12 for SYSENTER MSRs when they're written
KVM: nVMX: Update vmcs12 for MSR_IA32_DEBUGCTLMSR when it's written
KVM: nVMX: Update vmcs02 GUEST_IA32_DEBUGCTL only when vmcs12 is dirty
KVM: nVMX: Don't update GUEST_BNDCFGS if it's clean in HV eVMCS
KVM: nVMX: Copy PDPTRs to/from vmcs12 only when necessary

arch/x86/kvm/vmx/nested.c | 142 +++++++++++++++++++-------------------
arch/x86/kvm/vmx/vmx.c | 93 +++++++++++++++++--------
arch/x86/kvm/vmx/vmx.h | 5 +-
3 files changed, 136 insertions(+), 104 deletions(-)

--
2.21.0