Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
From:   Paul Durrant <xadimgnik@gmail.com>
Message-ID: <b47e82a4-2c01-4207-b4f8-296243061202@xen.org>
Date:   Thu, 2 Nov 2023 18:11:59 +0000
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Reply-To: paul@xen.org
Subject: Re: [PATCH v7 04/11] KVM: pfncache: base offset check on khva rather
 than gpa
Content-Language: en-US
To:     Sean Christopherson <seanjc@google.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Paul Durrant <pdurrant@amazon.com>,
        David Woodhouse <dwmw@amazon.co.uk>,
        David Woodhouse <dwmw2@infradead.org>,
        Paolo Bonzini <pbonzini@redhat.com>
References: <20231002095740.1472907-1-paul@xen.org>
 <20231002095740.1472907-5-paul@xen.org> <ZUGQhfH3HE-y6_5C@google.com>
Organization: Xen Project
In-Reply-To: <ZUGQhfH3HE-y6_5C@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 31/10/2023 23:40, Sean Christopherson wrote:
> On Mon, Oct 02, 2023, Paul Durrant wrote:
>> From: Paul Durrant <pdurrant@amazon.com>
>>
>> After a subsequent patch, the gpa may not always be set whereas khva will
>> (as long as the cache valid flag is also set).
> 
> This holds true only because there are no users of KVM_GUEST_USES_PFN, and
> because hva_to_pfn_retry() rather oddly adds the offset to a NULL khva.
> 
> I think it's time to admit using this to map PFNs into the guest is a bad idea
> and rip out KVM_GUEST_USES_PFN before fully relying on khva.
> 
> https://lore.kernel.org/all/ZQiR8IpqOZrOpzHC@google.com

Is this something you want me to fix?

   Paul