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Thu, 08 May 2025 14:01:12 -0700 (PDT) Received: from [192.168.101.134] ([75.147.178.105]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22fc680515esm4371185ad.0.2025.05.08.14.01.12 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 May 2025 14:01:12 -0700 (PDT) Message-ID: Date: Thu, 8 May 2025 14:01:10 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] target/i386: ignore misplaced REX prefixes To: qemu-devel@nongnu.org References: <20250508095436.471819-1-pbonzini@redhat.com> Content-Language: en-US From: Richard Henderson In-Reply-To: <20250508095436.471819-1-pbonzini@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::42a; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42a.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 5/8/25 02:54, Paolo Bonzini wrote: > Signed-off-by: Paolo Bonzini > --- > target/i386/tcg/decode-new.c.inc | 36 ++++++++++++++++++++++++-------- > 1 file changed, 27 insertions(+), 9 deletions(-) > > diff --git a/target/i386/tcg/decode-new.c.inc b/target/i386/tcg/decode-new.c.inc > index cda32ee6784..55216e0d249 100644 > --- a/target/i386/tcg/decode-new.c.inc > +++ b/target/i386/tcg/decode-new.c.inc > @@ -2542,7 +2542,13 @@ static void disas_insn(DisasContext *s, CPUState *cpu) > s->has_modrm = false; > s->prefix = 0; > > - next_byte: > + next_byte:; > +#ifdef TARGET_X86_64 > + /* clear any REX prefix followed by other prefixes. */ > + int rex; > + rex = -1; > + next_byte_rex: > +#endif > b = x86_ldub_code(env, s); I guess this is ok, with -1. It might be worthwhile rewriting without ifdefs, since we already let CODE64(s) and REX_PREFIX(s) expand to false without TARGET_X86_64. The only irritating part would be actually setting s->rex_* at the end, because those members are themselves ifdef'ed over in DisasContext. Reviewed-by: Richard Henderson r~