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([2001:b07:6468:f312:566:fc24:94f2:2f13]) by smtp.gmail.com with ESMTPSA id l18sm19087044wrn.48.2019.10.21.06.03.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Oct 2019 06:03:10 -0700 (PDT) Subject: Re: [PATCH v9 09/17] x86/split_lock: Handle #AC exception for split lock To: Sean Christopherson Cc: Xiaoyao Li , Thomas Gleixner , Fenghua Yu , Ingo Molnar , Borislav Petkov , H Peter Anvin , Peter Zijlstra , Andrew Morton , Dave Hansen , Radim Krcmar , Ashok Raj , Tony Luck , Dan Williams , Sai Praneeth Prakhya , Ravi V Shankar , linux-kernel , x86 , kvm@vger.kernel.org References: <3ec328dc-2763-9da5-28d6-e28970262c58@redhat.com> <57f40083-9063-5d41-f06d-fa1ae4c78ec6@redhat.com> <3a12810b-1196-b70a-aa2e-9fe17dc7341a@redhat.com> <20191016154116.GA5866@linux.intel.com> <20191016162337.GC5866@linux.intel.com> <20191016174200.GF5866@linux.intel.com> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: Date: Mon, 21 Oct 2019 15:03:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191016174200.GF5866@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/10/19 19:42, Sean Christopherson wrote: > KVM uses a locked cmpxchg in emulator_cmpxchg_emulated() and the address > is guest controlled, e.g. a guest could coerce the host into disabling > split-lock detection via the host's #AC handler by triggering emulation > and inducing an #AC in the emulator. Yes, that's a possible issue. Paolo