linux-kernel - Re: [PATCH] KVM: MMU: update comment on the number of page role combinations

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Message-ID: <85599dcde5c8c6b74437fac28ebb62c38dafc6a8.camel@redhat.com>
Date:   Tue, 16 Nov 2021 13:07:46 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: MMU: update comment on the number of page role
 combinations

On Tue, 2021-11-16 at 05:11 -0500, Paolo Bonzini wrote:
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e977634333d4..354fd2a918d5 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -291,9 +291,9 @@ struct kvm_kernel_irq_routing_entry;
>   * the number of unique SPs that can theoretically be created is 2^n, where n
>   * is the number of bits that are used to compute the role.
>   *
> - * But, even though there are 18 bits in the mask below, not all combinations
> + * But, even though there are 20 bits in the mask below, not all combinations
I to be honest counted 19 bits there (which includes the 'smm' bit), but I might have
made a mistake. I do wonder maybe it is better to just remove that comment with explicit
number?

Best regards,
	Maxim Levitsky


>   * of modes and flags are possible.  The maximum number of possible upper-level
> - * shadow pages for a single gfn is in the neighborhood of 2^13.
> + * shadow pages for a single gfn is in the neighborhood of 2^15.
>   *
>   *   - invalid shadow pages are not accounted.
>   *   - level is effectively limited to four combinations, not 16 as the number