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([2001:b07:6468:f312:3c1c:ffba:c624:29b8]) by smtp.gmail.com with ESMTPSA id qt19sm802316ejb.14.2020.05.28.03.43.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 May 2020 03:43:05 -0700 (PDT) Subject: Re: How to fuzz devices that use timers? To: Christophe de Dinechin , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= References: <93600c7c-ccd5-01b9-36d1-5631bfb63b7e@amsat.org> From: Paolo Bonzini Message-ID: Date: Thu, 28 May 2020 12:43:04 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/28 02:50:32 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Stefan Hajnoczi , =?UTF-8?Q?Alex_Benn=c3=a9e?= , "Dr. David Alan Gilbert" , qemu-devel , "Oleinik, Alexander" , Pavel Dovgalyuk , Artem Pisarenko Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 28/05/20 11:52, Christophe de Dinechin wrote: > > Since we run the fuzzer with the QTest accelerator, my first idea was to > check for 'if (qtest_enabled())' in the timer code, and directly expire > a timer instead of scheduling it. This way we can test reproducers. > However various tests require/verify precise timing, so this would break > various qtests. There is a clock_step command that advance the QEMU_CLOCK_VIRTUAL clock to the next deadline. You just have to insert it into the fuzzing input. Paolo