Re: [PATCH] KVM: x86/mmu: fix an incorrect comment in kvm_mmu_new_pgd

Sean Christopherson
2022-11-28T18:19:18Z

On Sun, Nov 27, 2022, Wei Liu wrote:
> There is no function named kvm_mmu_ensure_valid_pgd.

() when referecing functions, here and in the comment.

> Fix the comment and remove the pair of braces to conform to Linux kernel
> coding style.
>
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
> arch/x86/kvm/mmu/mmu.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index b6f96d47e596..361574124fbe 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4452,10 +4452,12 @@ void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd)
> struct kvm_mmu *mmu = vcpu->arch.mmu;
> union kvm_mmu_page_role new_role = mmu->root_role;
>
> - if (!fast_pgd_switch(vcpu->kvm, mmu, new_pgd, new_role)) {
> - /* kvm_mmu_ensure_valid_pgd will set up a new root. */
> + /*
> + * Return immediately if no usable root is found. A new root will be

s/is/was

And technically, it may not be a "new" root, e.g. if a different vCPU creates a
usable root between now and kvm_mmu_reload().

> + * set up in vcpu_enter_guest prior to the next vmenter.

s/vmenter/VM-Enter

Pointing a reader at vcpu_enter_guest() isn't very helpful since that's a massive
function; kvm_mmu_reload() is where the real magic happens. I generally prefer to
avoid referencing functions in comments unless doing so is absolutely "necessary"
because such comments always seem to become stale, but in this case I think it's
worthwhile.

/*
* Return immediately if no usable was found, kvm_mmu_reload() will
* establish a valid root prior to the next VM-Enter.
*/

> + */
> + if (!fast_pgd_switch(vcpu->kvm, mmu, new_pgd, new_role))
> return;
> - }
>
> /*
> * It's possible that the cached previous root page is obsolete because
> --
> 2.35.1
>