Re: [PATCH v4 18/25] KVM: VMX: Add missing CPU based VM execution controls to vmcs_config

Sean Christopherson
2022-07-21T22:39:10Z

On Thu, Jul 14, 2022, Vitaly Kuznetsov wrote:
> As a preparation to reusing the result of setup_vmcs_config() in
> nested VMX MSR setup, add the CPU based VM execution controls which KVM
> doesn't use but supports for nVMX to KVM_OPT_VMX_CPU_BASED_VM_EXEC_CONTROL
> and filter them out in vmx_exec_control().
>
> No functional change intended.
>
> Reviewed-by: Jim Mattson <jmattson@google.com>
> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 6 ++++++
> arch/x86/kvm/vmx/vmx.h | 6 +++++-
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 2fb89bdcbbd8..9771c771c8f5 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -4240,6 +4240,12 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx)
> {
> u32 exec_control = vmcs_config.cpu_based_exec_ctrl;
>
> + /* Not used by KVM but supported for nesting. */

And then for this one, clarify that these _are_ enabled in vmcs02. It doesn't
really matter, I was just surprised by the "SAVE_PAT" in the previous patch because
for a second I thought we were leaking host state :-)

/*
* Not used by KVM, but fully supported for nesting, i.e. are allowed in
* vmcs12 and propagated to vmcs02 when set in vmcs12.
*/

> + exec_control &= ~(CPU_BASED_RDTSC_EXITING |
> + CPU_BASED_USE_IO_BITMAPS |
> + CPU_BASED_MONITOR_TRAP_FLAG |
> + CPU_BASED_PAUSE_EXITING);
> +
> /* INTR_WINDOW_EXITING and NMI_WINDOW_EXITING are toggled dynamically */
> exec_control &= ~(CPU_BASED_INTR_WINDOW_EXITING |
> CPU_BASED_NMI_WINDOW_EXITING);
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index e9c392398f1b..758f80c41beb 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -539,9 +539,13 @@ static inline u8 vmx_get_rvi(void)
> #endif
>
> #define KVM_OPT_VMX_CPU_BASED_VM_EXEC_CONTROL \
> - (CPU_BASED_TPR_SHADOW | \
> + (CPU_BASED_RDTSC_EXITING | \
> + CPU_BASED_TPR_SHADOW | \
> + CPU_BASED_USE_IO_BITMAPS | \
> + CPU_BASED_MONITOR_TRAP_FLAG | \
> CPU_BASED_USE_MSR_BITMAPS | \
> CPU_BASED_NMI_WINDOW_EXITING | \
> + CPU_BASED_PAUSE_EXITING | \
> CPU_BASED_ACTIVATE_SECONDARY_CONTROLS | \
> CPU_BASED_ACTIVATE_TERTIARY_CONTROLS)
>
> --
> 2.35.3
>