Re: [PATCH v6 2/4] KVM: mmu: add a helper to account memory used by KVM MMU.

[Sean Christopherson <seanjc-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>]

On Tue, Jun 28, 2022, Yosry Ahmed wrote:
> Add a helper to account pages used by KVM for page tables in memory
> secondary pagetable stats. This function will be used by subsequent
> patches in different archs.
> 
> Signed-off-by: Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> ---
>  include/linux/kvm_host.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 3b40f8d68fbb1..032821d77e920 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2241,6 +2241,16 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
>  }
>  #endif /* CONFIG_KVM_XFER_TO_GUEST_WORK */
>  
> +/*
> + * If more than one page is being (un)accounted, @virt must be the address of
> + * the first page of a block of pages what were allocated together (i.e
> + * accounted together).

Sorry for the belated thoughts...

If you spin a v7, can you add a note to call out that mod_lruvec_page_state() is
itself thread-safe?  Caught my eye because the TDP MMU usage happens while holding
mmu_lock for read.

> + */
> +static inline void kvm_account_pgtable_pages(void *virt, int nr)
> +{
> +	mod_lruvec_page_state(virt_to_page(virt), NR_SECONDARY_PAGETABLE, nr);
> +}
> +
>  /*
>   * This defines how many reserved entries we want to keep before we
>   * kick the vcpu to the userspace to avoid dirty ring full.  This
> -- 
> 2.37.0.rc0.161.g10f37bed90-goog
>