On 01/31/2018 05:50 PM, Jim Mattson wrote:
On Wed, Jan 31, 2018 at 5:10 AM, KarimAllah Ahmed <karahmed@xxxxxxxxx> wrote:
+ vmx_disable_intercept_for_msr(vmx->vmcs01.msr_bitmap, MSR_IA32_PRED_CMD,
+ MSR_TYPE_W);
Why not disable this intercept eagerly, rather than lazily? Unlike
MSR_IA32_SPEC_CTRL, there is no guest value to save/restore, so there
is no cost to disabling the intercept if the guest cpuid info declares
support for it.
+ if (to_vmx(vcpu)->save_spec_ctrl_on_exit) {
+ nested_vmx_disable_intercept_for_msr(
+ msr_bitmap_l1, msr_bitmap_l0,
+ MSR_IA32_PRED_CMD,
+ MSR_TYPE_R);
+ }
I don't think this should be predicated on
"to_vmx(vcpu)->save_spec_ctrl_on_exit." Why not just
"guest_cpuid_has(vcpu, X86_FEATURE_IBPB)"?
Paolo suggested this on the previous revision because guest_cpuid_has()
would be slow.
Also, the final argument to
nested_vmx_disable_intercept_for_msr should be MSR_TYPE_W rather than
MSR_TYPE_R.
Oops! will fix!
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