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([2001:b07:6468:f312:9af8:e5f5:7516:fa89]) by smtp.googlemail.com with ESMTPSA id s6-20020a170906bc4600b007aed2057eaesm3774436ejv.161.2022.11.14.08.58.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Nov 2022 08:58:02 -0800 (PST) Message-ID: Date: Mon, 14 Nov 2022 17:58:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Content-Language: en-US To: "Woodhouse, David" , "seanjc@google.com" Cc: "mhal@rbox.co" , "kvm@vger.kernel.org" , "Durrant, Paul" , "linux-kernel@vger.kernel.org" , "Kaya, Metin" References: <20221027161849.2989332-1-pbonzini@redhat.com> <20221027161849.2989332-4-pbonzini@redhat.com> <994314051112513787cc4bd0c7d2694e15190d0f.camel@amazon.co.uk> From: Paolo Bonzini Subject: Re: [PATCH 03/16] KVM: x86: set gfn-to-pfn cache length consistently with VM word size In-Reply-To: <994314051112513787cc4bd0c7d2694e15190d0f.camel@amazon.co.uk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/14/22 15:53, Woodhouse, David wrote: > Most other data structures, including the pvclock info (both Xen and > native KVM), could potentially cross page boundaries. And isn't that > also true for things that we'd want to use the GPC for in nesting? Yes, for kvmclock we likely got away with it because Linux page-aligns it (and has been since 2013: commit ed55705dd, originally done for vsyscall support). I have checked OpenBSD and FreeBSD and I think they do as well. I am very very tempted to remove support for "old-style" kvmclock MSRs and retroactively declare new-style MSRs to accept only 32-byte aligned addresses. However that doesn't solve the problem. Paolo