Re: [PATCH kernel] KVM: SVM: Fix function name in comment

[Sean Christopherson <seanjc@google.com>]

On Mon, Sep 12, 2022, Alexey Kardashevskiy wrote:
> A recent renaming patch missed 1 spot, fix it.
> 
> This should cause no behavioural change.
> 
> Fixes: 23e5092b6e2a ("KVM: SVM: Rename hook implementations to conform to kvm_x86_ops' names")
> Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
> ---
>  arch/x86/kvm/svm/sev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 28064060413a..3b99a690b60d 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -3015,7 +3015,7 @@ void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa)
>  	/*
>  	 * As an SEV-ES guest, hardware will restore the host state on VMEXIT,
>  	 * of which one step is to perform a VMLOAD.  KVM performs the
> -	 * corresponding VMSAVE in svm_prepare_guest_switch for both
> +	 * corresponding VMSAVE in svm_prepare_switch_to_guest for both
>  	 * traditional and SEV-ES guests.
>  	 */

Rather than match the rename, what about tweaking the wording to not tie the comment
to the function name, e.g. "VMSAVE in common SVM code".

Even better, This would be a good opportunity to reword this comment to make it more
clear why SEV-ES needs a hook, and to absorb the somewhat useless comments below.

Would something like this be accurate?  Please modify and/or add details as necessary.

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 3b99a690b60d..c50c6851aedb 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3013,19 +3013,14 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm)
 void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa)
 {
        /*
-        * As an SEV-ES guest, hardware will restore the host state on VMEXIT,
-        * of which one step is to perform a VMLOAD.  KVM performs the
-        * corresponding VMSAVE in svm_prepare_switch_to_guest for both
-        * traditional and SEV-ES guests.
+        * Manually save host state that is automatically loaded by hardware on
+        * VM-Exit from SEV-ES guests, but that is not saved by VMSAVE (which is
+        * performed by common SVM code).  Hardware unconditionally restores
+        * host state, and so KVM skips manually restoring this state in common
+        * code.
         */
-
-       /* XCR0 is restored on VMEXIT, save the current host value */
        hostsa->xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
-
-       /* PKRU is restored on VMEXIT, save the current host value */
        hostsa->pkru = read_pkru();
-
-       /* MSR_IA32_XSS is restored on VMEXIT, save the currnet host value */
        hostsa->xss = host_xss;
 }