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[176.184.7.255]) by smtp.gmail.com with ESMTPSA id l17-20020a05600012d100b00314329f7d8asm2584387wrx.29.2023.08.10.08.53.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Aug 2023 08:53:21 -0700 (PDT) Message-ID: Date: Thu, 10 Aug 2023 17:53:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH for-8.1] accel/tcg: Avoid reading too much in load_atom_{2,4} Content-Language: en-US To: Richard Henderson , qemu-devel@nongnu.org Cc: Mark Cave-Ayland References: <20230810154802.16663-1-richard.henderson@linaro.org> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= In-Reply-To: <20230810154802.16663-1-richard.henderson@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::433; envelope-from=philmd@linaro.org; helo=mail-wr1-x433.google.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 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=-2.156, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 10/8/23 17:48, Richard Henderson wrote: > When load_atom_extract_al16_or_al8 is inexpensive, we want to use > it early, in order to avoid the overhead of required_atomicity. > However, we must not read past the end of the page. > > Reported-by: Mark Cave-Ayland > Signed-off-by: Richard Henderson > --- > diff --git a/accel/tcg/ldst_atomicity.c.inc b/accel/tcg/ldst_atomicity.c.inc > index e5c590a499..5d92485a49 100644 > --- a/accel/tcg/ldst_atomicity.c.inc > +++ b/accel/tcg/ldst_atomicity.c.inc > @@ -404,7 +404,10 @@ static uint16_t load_atom_2(CPUArchState *env, uintptr_t ra, > return load_atomic2(pv); > } > if (HAVE_ATOMIC128_RO) { > - return load_atom_extract_al16_or_al8(pv, 2); > + intptr_t left_in_page = pi | TARGET_PAGE_MASK; > + if (likely(left_in_page <= -16)) { > + return load_atom_extract_al16_or_al8(pv, 2); > + } > } > > atmax = required_atomicity(env, pi, memop); > @@ -443,7 +446,10 @@ static uint32_t load_atom_4(CPUArchState *env, uintptr_t ra, > return load_atomic4(pv); > } > if (HAVE_ATOMIC128_RO) { > - return load_atom_extract_al16_or_al8(pv, 4); > + intptr_t left_in_page = pi | TARGET_PAGE_MASK; > + if (likely(left_in_page <= -16)) { > + return load_atom_extract_al16_or_al8(pv, 4); > + } > } Makes sense, so to the best of my knowledge: Reviewed-by: Philippe Mathieu-Daudé