linux-kernel - Re: [PATCH 3/3] KVM: Explicitly disallow activatating a gfn_to_pfn_cache with INVALID

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Message-ID: <0a1d48f9-7628-4c70-ba83-efb6263f6bfa@xen.org>
Date: Thu, 21 Mar 2024 11:13:05 +0000
From: Paul Durrant <xadimgnik@...il.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot+106a4f72b0474e1d1b33@...kaller.appspotmail.com,
 David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 3/3] KVM: Explicitly disallow activatating a
 gfn_to_pfn_cache with INVALID_GPA

On 20/03/2024 00:15, Sean Christopherson wrote:
> Explicit disallow activating a gfn_to_pfn_cache with an error gpa, i.e.
> INVALID_GPA, to ensure that KVM doesn't mistake a GPA-based cache for an
> HVA-based cache (KVM uses INVALID_GPA as a magic value to differentiate
> between GPA-based and HVA-based caches).
> 
> WARN if KVM attempts to activate a cache with INVALID_GPA, purely so that
> new caches need to at least consider what to do with a "bad" GPA, as all
> existing usage of kvm_gpc_activate() guarantees gpa != INVALID_GPA.  I.e.
> removing the WARN in the future is completely reasonable if doing so would
> yield cleaner/better code overall.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   virt/kvm/pfncache.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 

Reviewed-by: Paul Durrant <paul@....org>