| Message ID | 20180926162358.10741-14-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: nVMX: add option to perform early consistency checks via H/W | expand |
On Wed, Sep 26, 2018 at 9:23 AM, Sean Christopherson <sean.j.christopherson@intel.com> wrote: > Add a dedicated flag to track if vmcs02 has been initialized, i.e. > the constant state for vmcs02 has been written to the backing VMCS. > The launched flag (in struct loaded_vmcs) gets cleared on logical > CPU migration to mirror hardware behavior[1], i.e. using the launched > flag to determine whether or not vmcs02 constant state needs to be > initialized results in unnecessarily re-initializing the VMCS when > migrating between logical CPUS. > > [1] The active VMCS needs to be VMCLEARed before it can be migrated > to a different logical CPU. Hardware's VMCS cache is per-CPU > and is not coherent between CPUs. VMCLEAR flushes the cache so > that any dirty data is written back to memory. A side effect > of VMCLEAR is that it also clears the VMCS's internal launch > flag, which KVM must mirror because VMRESUME must be used to > run a previously launched VMCS. > > Suggested-by: Jim Mattson <jmattson@google.com> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by: Jim Mattson <jmattson@google.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 702d4f51fa53..5a2566ee4975 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -833,6 +833,13 @@ struct nested_vmx { bool sync_shadow_vmcs; bool dirty_vmcs12; + /* + * vmcs02 has been initialized, i.e. state that is constant for + * vmcs02 has been written to the backing VMCS. Initialization + * is delayed until L1 actually attempts to run a nested VM. + */ + bool vmcs02_initialized; + bool change_vmcs01_virtual_apic_mode; /* L2 must run next, and mustn't decide to exit to L1. */ @@ -8278,6 +8285,7 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu) vmx->nested.vpid02 = allocate_vpid(); + vmx->nested.vmcs02_initialized = false; vmx->nested.vmxon = true; return 0; @@ -11907,13 +11915,14 @@ static u64 nested_vmx_calc_efer(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12) static void prepare_vmcs02_constant_state(struct vcpu_vmx *vmx) { /* - * If we have never launched vmcs02, set the constant vmcs02 state + * If vmcs02 hasn't been initialized, set the constant vmcs02 state * according to L0's settings (vmcs12 is irrelevant here). Host * fields that come from L0 and are not constant, e.g. HOST_CR3, * will be set as needed prior to VMLAUNCH/VMRESUME. */ - if (vmx->nested.vmcs02.launched) + if (vmx->nested.vmcs02_initialized) return; + vmx->nested.vmcs02_initialized = true; /* All VMFUNCs are currently emulated through L0 vmexits. */ if (cpu_has_vmx_vmfunc())
Add a dedicated flag to track if vmcs02 has been initialized, i.e. the constant state for vmcs02 has been written to the backing VMCS. The launched flag (in struct loaded_vmcs) gets cleared on logical CPU migration to mirror hardware behavior[1], i.e. using the launched flag to determine whether or not vmcs02 constant state needs to be initialized results in unnecessarily re-initializing the VMCS when migrating between logical CPUS. [1] The active VMCS needs to be VMCLEARed before it can be migrated to a different logical CPU. Hardware's VMCS cache is per-CPU and is not coherent between CPUs. VMCLEAR flushes the cache so that any dirty data is written back to memory. A side effect of VMCLEAR is that it also clears the VMCS's internal launch flag, which KVM must mirror because VMRESUME must be used to run a previously launched VMCS. Suggested-by: Jim Mattson <jmattson@google.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/vmx.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)