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[174.21.76.141]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-72c6afb9042sm1751994a12.41.2024.06.28.15.35.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Jun 2024 15:35:42 -0700 (PDT) Message-ID: Date: Fri, 28 Jun 2024 15:35:40 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/23] target/i386: fix gen_prepare_size_nz condition From: Richard Henderson To: =?UTF-8?Q?Alex_Benn=C3=A9e?= , qemu-devel@nongnu.org, Paolo Bonzini References: <20240628124258.832466-1-alex.bennee@linaro.org> <20240628124258.832466-3-alex.bennee@linaro.org> <627f05b5-7abe-423f-829e-4215bcf1bccd@linaro.org> Content-Language: en-US In-Reply-To: <627f05b5-7abe-423f-829e-4215bcf1bccd@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::42c; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42c.google.com 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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 6/28/24 10:54, Richard Henderson wrote: > On 6/28/24 05:42, Alex Bennée wrote: >> Incorrect brace positions causes an unintended overflow on 32 bit >> builds and shenanigans result. >> >> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2413 >> Suggested-by: Mark Cave-Ayland >> Signed-off-by: Alex Bennée >> --- >>   target/i386/tcg/translate.c | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c >> index ad1819815a..94f13541c3 100644 >> --- a/target/i386/tcg/translate.c >> +++ b/target/i386/tcg/translate.c >> @@ -877,7 +877,7 @@ static CCPrepare gen_prepare_sign_nz(TCGv src, MemOp size) >>           return (CCPrepare) { .cond = TCG_COND_LT, .reg = src }; >>       } else { >>           return (CCPrepare) { .cond = TCG_COND_TSTNE, .reg = src, >> -                             .imm = 1ull << ((8 << size) - 1) }; >> +                             .imm = (1ull << (8 << size)) - 1 }; > > This is incorrect -- we want only to test the sign bit. > Perhaps MAKE_64BIT_MASK((8 << size) - 1, 1) would make this more explicit? > > I'll have a quick look at the issue and see if I can reproduce. I can't get the cdrom test to run at all; I have no idea why. 1/1 qemu:qtest+qtest-x86_64 / qtest-x86_64/cdrom-test SKIP 0.00s But QTEST_QEMU_BINARY='./qemu-system-x86_64' ./tests/qtest/bios-tables-test -v -p /x86_64/acpi/q35/mmio64 fails for me, and is resolved at 15957eb9e by reverting diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c index 4735f084d4..022469845e 100644 --- a/target/i386/tcg/translate.c +++ b/target/i386/tcg/translate.c @@ -1084,13 +1084,8 @@ static CCPrepare gen_prepare_eflags_z(DisasContext *s, TCGv reg) default: { MemOp size = (s->cc_op - CC_OP_ADDB) & 3; - if (size == MO_TL) { - return (CCPrepare) { .cond = TCG_COND_EQ, .reg = cpu_cc_dst, - .mask = -1 }; - } else { - return (CCPrepare) { .cond = TCG_COND_TSTEQ, .reg = cpu_cc_dst, - .mask = -1, .imm = (1ull << (8 << size)) - 1 }; - } + TCGv t0 = gen_ext_tl(reg, cpu_cc_dst, size, false); + return (CCPrepare) { .cond = TCG_COND_EQ, .reg = t0, .mask = -1 }; } } } I fought all afternoon to try and debug this, but was defeated by qtest. I really wish we could change our tooling to simplify debugging. r~