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[54.240.197.226]) by smtp.gmail.com with ESMTPSA id fl25-20020a05600c0b9900b00414778ca80fsm122464wmb.16.2024.03.21.04.07.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Mar 2024 04:07:51 -0700 (PDT) From: Paul Durrant X-Google-Original-From: Paul Durrant Message-ID: Date: Thu, 21 Mar 2024 11:07:50 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: paul@xen.org Subject: Re: [PATCH 1/3] KVM: Add helpers to consolidate gfn_to_pfn_cache's page split check Content-Language: en-US To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com, David Woodhouse References: <20240320001542.3203871-1-seanjc@google.com> <20240320001542.3203871-2-seanjc@google.com> Organization: Xen Project In-Reply-To: <20240320001542.3203871-2-seanjc@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 20/03/2024 00:15, Sean Christopherson wrote: > Add a helper to check that the incoming length for a gfn_to_pfn_cache is > valid with respect to the cache's GPA and/or HVA. To avoid activating a > cache with a bogus GPA, a future fix will fork the page split check in > the inner refresh path into activate() and the public rerfresh() APIs, at nit: typo > which point KVM will check the length in three separate places. > > Deliberately keep the "page offset" logic open coded, as the only other > path that consumes the offset, __kvm_gpc_refresh(), already needs to > differentiate between GPA-based and HVA-based caches, and it's not obvious > that using a helper is a net positive in overall code readability. > > Note, for GPA-based caches, this has a subtle side effect of using the GPA > instead of the resolved HVA in the check() path, but that should be a nop > as the HVA offset is derived from the GPA, i.e. the two offsets are > identical, barring a KVM bug. > > Signed-off-by: Sean Christopherson > --- > virt/kvm/pfncache.c | 27 +++++++++++++++++++-------- > 1 file changed, 19 insertions(+), 8 deletions(-) > Reviewed-by: Paul Durrant