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Sun, 22 Aug 2021 00:48:15 -0700 (PDT) Received: from [192.168.1.11] ([71.212.149.176]) by smtp.gmail.com with ESMTPSA id s5sm14646527pgp.81.2021.08.22.00.48.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Aug 2021 00:48:15 -0700 (PDT) Subject: Re: [PATCH v3 59/66] accel/tcg: Handle SIGBUS in handle_cpu_signal To: Peter Maydell References: <20210818191920.390759-1-richard.henderson@linaro.org> <20210818191920.390759-60-richard.henderson@linaro.org> From: Richard Henderson Message-ID: <85cba917-3b5b-8a8d-088a-1dfeb8787ef0@linaro.org> Date: Sun, 22 Aug 2021 00:48:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::62d; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x62d.google.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-1.49, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/20/21 2:34 AM, Peter Maydell wrote: > On Wed, 18 Aug 2021 at 21:13, Richard Henderson > wrote: >> >> We've been registering host SIGBUS, but then treating it >> exactly like SIGSEGV. >> >> Handle BUS_ADRALN via cpu_unaligned_access, but allow other >> SIGBUS si_codes to continue into the host-to-guest signal >> coversion code in host_signal_handler. Unwind the guest >> state so that we report the correct guest PC for the fault. > > You can't rely on alignment faults being marked by BUS_ADRALN: > eg MIPS doesn't give you that si_code. How much does that matter > for our use of it here ? Aside from whatever tcg/foo relies upon, it doesn't matter. But: silly mips. I was going to rely on it there -- oh well, I'll undo that section of the follow-on tcg/mips patch set. And it's got a different syscall for disabling the unaligned fixup. r~