Re: [PATCH v7 1/3] KVM: x86: add support for user wait instructions

From: Sean Christopherson
Date: Fri Jul 12 2019 - 11:13:03 EST


On Fri, Jul 12, 2019 at 04:29:05PM +0800, Tao Xu wrote:
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 46af3a5e9209..a4d5da34b306 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -2048,6 +2048,7 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
> SECONDARY_EXEC_ENABLE_INVPCID |
> SECONDARY_EXEC_RDTSCP |
> SECONDARY_EXEC_XSAVES |
> + SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE |
> SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
> SECONDARY_EXEC_APIC_REGISTER_VIRT |
> SECONDARY_EXEC_ENABLE_VMFUNC);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d98eac371c0a..f411c9ae5589 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2247,6 +2247,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> SECONDARY_EXEC_RDRAND_EXITING |
> SECONDARY_EXEC_ENABLE_PML |
> SECONDARY_EXEC_TSC_SCALING |
> + SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE |
> SECONDARY_EXEC_PT_USE_GPA |
> SECONDARY_EXEC_PT_CONCEAL_VMX |
> SECONDARY_EXEC_ENABLE_VMFUNC |
> @@ -3984,6 +3985,25 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
> }
> }
>
> + if (vmcs_config.cpu_based_2nd_exec_ctrl &
> + SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE) {

This should be aligned with the beginning of the conditional.
Alternatively, add a vmx_waitpkg_supported() helper, which is fairly
ubiquitous even when there is only a single call site.

> + /* Exposing WAITPKG only when WAITPKG is exposed */
No need for this comment. It's also oddly worded, e.g. the second
"exposed" should probably be "enabled"?

> + bool waitpkg_enabled =
> + guest_cpuid_has(vcpu, X86_FEATURE_WAITPKG);
> +
> + if (!waitpkg_enabled)
> + exec_control &= ~SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
> +
> + if (nested) {
> + if (waitpkg_enabled)
> + vmx->nested.msrs.secondary_ctls_high |=
> + SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
> + else
> + vmx->nested.msrs.secondary_ctls_high &=
> + ~SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
> + }
> + }
> +
> vmx->secondary_exec_control = exec_control;
> }
>
> --
> 2.20.1
>