linux-kernel - Re: [RFC PATCH v3 06/19] KVM: x86: mmu: add gfn_in

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Message-ID: <YoZzx6f1XBWL3i8F@google.com>
Date:   Thu, 19 May 2022 16:43:51 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        intel-gfx@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Brijesh Singh <brijesh.singh@....com>,
        "H. Peter Anvin" <hpa@...or.com>,
        intel-gvt-dev@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [RFC PATCH v3 06/19] KVM: x86: mmu: add gfn_in_memslot helper

On Wed, Apr 27, 2022, Maxim Levitsky wrote:
> This is a tiny refactoring, and can be useful to check
> if a GPA/GFN is within a memslot a bit more cleanly.

This doesn't explain the actual motivation, which is to use the new helper from
arch code.

> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>  include/linux/kvm_host.h | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 252ee4a61b58b..12e261559070b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1580,6 +1580,13 @@ int kvm_request_irq_source_id(struct kvm *kvm);
>  void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id);
>  bool kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args);
>  
> +
> +static inline bool gfn_in_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
> +{
> +	return (gfn >= slot->base_gfn && gfn < slot->base_gfn + slot->npages);
> +}
> +

Spurious newline.

> +
>  /*
>   * Returns a pointer to the memslot if it contains gfn.
>   * Otherwise returns NULL.
> @@ -1590,12 +1597,13 @@ try_get_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
>  	if (!slot)
>  		return NULL;
>  
> -	if (gfn >= slot->base_gfn && gfn < slot->base_gfn + slot->npages)
> +	if (gfn_in_memslot(slot, gfn))
>  		return slot;
>  	else
>  		return NULL;

At this point, maybe:

	if (!slot || !gfn_in_memslot(slot, gfn))
		return NULL;

	return slot;

>  }
>  
> +
>  /*
>   * Returns a pointer to the memslot that contains gfn. Otherwise returns NULL.
>   *
> -- 
> 2.26.3
>