{"id":2196513,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2196513/?format=json","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.0/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260214131659.31378-4-shentey@gmail.com>","date":"2026-02-14T13:16:59","name":"[3/3] target/i386/emulate/x86_decode: Actually use stream in decode_instruction_stream()","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"618c4fc9a5befdd72b0c76792e2b6d1f676047d5","submitter":{"id":83251,"url":"http://patchwork.ozlabs.org/api/1.0/people/83251/?format=json","name":"Bernhard Beschow","email":"shentey@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260214131659.31378-4-shentey@gmail.com/mbox/","series":[{"id":492172,"url":"http://patchwork.ozlabs.org/api/1.0/series/492172/?format=json","date":"2026-02-14T13:16:58","name":"i386 emulate fixes","version":1,"mbox":"http://patchwork.ozlabs.org/series/492172/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2196513/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20230601 header.b=Smchuys8;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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helo=mail-wr1-x431.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,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n 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":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"Compared to decode_instruction(), decode_instruction_stream() has an additional\nstream parameter which avoids some guest memory accesses during instruction\ndecoding. Both functions defer the actual work to decode_opcode() which would\nset the stream pointer to zero such that decode_instruction_stream() essentially\nbehaved like decode_instruction(). Given that all callers of\ndecode_instruction_stream() properly zero-initialize the decode parameter, the\nmemset() call can be moved into decode_instruction() which is the only other\nuser of decode_opcode(). This preserves the non-zero stream pointer which\navoids extra guest memory accesses.\n\nFixes: 1e25327b244a (\"target/i386/emulate: Allow instruction decoding from stream\")\ncc: qemu-stable\nSigned-off-by: Bernhard Beschow \n---\n target/i386/emulate/x86_decode.c | 4 ++--\n 1 file changed, 2 insertions(+), 2 deletions(-)","diff":"diff --git a/target/i386/emulate/x86_decode.c b/target/i386/emulate/x86_decode.c\nindex 6ad03b71b0..7bbcd2a9a2 100644\n--- a/target/i386/emulate/x86_decode.c\n+++ b/target/i386/emulate/x86_decode.c\n@@ -2088,8 +2088,6 @@ static void decode_opcodes(CPUX86State *env, struct x86_decode *decode)\n \n static uint32_t decode_opcode(CPUX86State *env, struct x86_decode *decode)\n {\n- memset(decode, 0, sizeof(*decode));\n-\n decode_prefix(env, decode);\n set_addressing_size(env, decode);\n set_operand_size(env, decode);\n@@ -2101,6 +2099,8 @@ static uint32_t decode_opcode(CPUX86State *env, struct x86_decode *decode)\n \n uint32_t decode_instruction(CPUX86State *env, struct x86_decode *decode)\n {\n+ memset(decode, 0, sizeof(*decode));\n+\n return decode_opcode(env, decode);\n }\n \n","prefixes":["3/3"]}