From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CAAC636A022 for ; Tue, 11 Nov 2025 16:55:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762880141; cv=none; b=eVKvyZvHz07BPdoN0IlAD3ytnL7sR7RPDVd1JT6kCg1uTJQzMN4hgjytiEpejtNpQR3aPU0CsMbT8WQZVKZYOUBx3EgSXBTlW5c/yAKS747V64Ek9570TawmuVdF1ifKDwCLyNR+dz2LnnfbEu5h2h4ySzryQ9mQ+7fhWcPAhIg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762880141; c=relaxed/simple; bh=nlEfTmws0Q46o78NUfhpjE3w9PAskdTxv3a88lJzlpU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=aexdao6X61C0EzGiU3zbtq+o/0C7sv2Tv+DngggXam72aG/rDZLJH0Bxc95B4wKbH3UkSVHk3SqJRAlE1+Pgmv/Isbpk/APhJ/JJeIVRQ88GKF5cP2/x/5apftof2B47OAwq0zBBv2C8zpTbYtSFxcrKN/RUIWt98IuFYnWIcoQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=b1js4xGl; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=BUXpbIAi; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="b1js4xGl"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="BUXpbIAi" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762880138; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=gnMIv0Ik+hITHUqF7t+6yoyTUpUVXjJtFWV6UcASCo0=; b=b1js4xGlbKUSGz3rtJp2zOMe8x77+rZvE9HrYlFpounWmIxWIVhPEEvg2/u/pRLK10kMeR 4eHkveRNxwVdZH0rMP4knXLirU8D1qyZdqH1VMTZ9wYaIPP17qbToIiSwnX7v+ikzAizZc /fdNd4cw6zo7jRyuK0fk6xt7t5VYKRo= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-553-R3_Xg6a5M6-zXB7nCWX3Ng-1; Tue, 11 Nov 2025 11:55:37 -0500 X-MC-Unique: R3_Xg6a5M6-zXB7nCWX3Ng-1 X-Mimecast-MFC-AGG-ID: R3_Xg6a5M6-zXB7nCWX3Ng_1762880136 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-42b2b642287so1781786f8f.2 for ; Tue, 11 Nov 2025 08:55:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1762880136; x=1763484936; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:from:to:cc:subject:date:message-id:reply-to; bh=gnMIv0Ik+hITHUqF7t+6yoyTUpUVXjJtFWV6UcASCo0=; b=BUXpbIAi4TzFpdEinFY81Q/MYpNv6s5W/kRxFAC2GPgT7AgQrAa/1YnyGqPT3NFvkw RsWZE5KdNsBPHD2MI8FEc5jQIn0U33eqJQIyG/fZqzxUjeYQb2LRVG6SHqXHFhFQdS1t RMXcVziQkC6+eJSDzaNpLA64Z1Rkc6Yqyw5whMW9VqCIhTTEcXe5i56TYp+nvY+WOJi7 QOR0RCsZXYCKozEb7Nnn/r/VqMaviS02n5VsrjjEu4iXPFMBI6kwHppk3cOu2waqq5C4 1KvkFRtQ36rXZyD75aYAXD3A3WNJKyFImc6D+5NMLWo59Cau91HXleSnPYVO4nGK8jYk eJ5A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1762880136; x=1763484936; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gnMIv0Ik+hITHUqF7t+6yoyTUpUVXjJtFWV6UcASCo0=; b=rh8K2o1+SSgxzQichFIRIr8GdUT51T/ZjEhP3JtqQdbz5Yj2v7dWveaagaPo9PQRd2 TU/NicQg2M+qOu+rnI35KCoHGbzxGWP7QI9p2D2yimo1fFyGLo+BLl4+HMLXtQFMGVFU 3BFLPiWwYY9bdPDupY6fHX9CWA1Q2/xhwh9AtirHg32wfNtZltdWpQ4UU0/W+mxx57S/ UiFnKhWZ4mbIlWDs5cuD7s8ZA9LGry8+RDx3pMQBQrkOyybosl5VlCc69lG4xAHsMDxD YbEsb+S33/pWOC1aMfuKLfonrgqHmCn3YwxXJmoQaTG+dy/7va4gA4pgVlVlQ6TsHEtn Dg0g== X-Forwarded-Encrypted: i=1; AJvYcCW0FA8FzJ8OeGILR/0PMZ4bbFArnoRKQu5XsgqUvnunYWbK85PLqEwGpSWOU7aBxjVoxQCAAfPUzitDjB4=@vger.kernel.org X-Gm-Message-State: AOJu0YxRySnRBh7WLI2RjYlwx9Vm7l3eyRSpJ680/EFoUrxkSNgYRE0t pGCA6X4RtLm0mhv9MvjptffaBl5xWGaHBPQsobcOOcXUUJRZF9OILZ0LL2RHpYdZE5OZl4n/xIY 72yBgo0+9wx8qFxH1o1TEKIXqiPp+qBmh5Yi4Y4wAytFtbSK2GtSjwv87U/f4ij4UHw== X-Gm-Gg: ASbGnctc2H04a0qzD94Z7vJAR3fBTJr/miE010AvTKnqTNB0ZM9sGbS7rjH53GVTZ1w 4IHAmY7/Yc1jn1+u1841UQ5hbUVi97dPWsig+McMN3+Z7Et6mpkU4xgb5vQyyjgHxGzswMb43J1 2tSuLLScL/rAbwfOrzCBj/QOJ+KN6djRIkjDY1uf3pz4axxtakb3Ks/5Pp1Jqw+PxbXuzhUnP9m QKR9O3szcJRaWQvuKRrjOTMPMhmdoED3oYWj7zOxoDum1n9iHYRa2jPndhUGkrdUgwoOZl289WM fWX5DZ5v1LZFNASdsYvju3OCOdaFr6IoXjVp4UO4J1n/TwqfuktqO+DFIWHIw05yoWg7UNqesUj vEC/oNFW4uivEW2TBMDrtg3a6vPxM47+4UtpRn6Fn7U3JLhIf/Pr2JAmhBlb6NwCzLSTrvNqU07 zscL0Eyg== X-Received: by 2002:a05:6000:144e:b0:42b:3bfc:d5cb with SMTP id ffacd0b85a97d-42b3bfcde1bmr6451770f8f.51.1762880136107; Tue, 11 Nov 2025 08:55:36 -0800 (PST) X-Google-Smtp-Source: AGHT+IEwXz8O+8CJxSCaosY+x8WzSmDIqFBYmIyaTJkW/+khTeoschvxJNMBqDWOCSADXh+6y0zXnQ== X-Received: by 2002:a05:6000:144e:b0:42b:3bfc:d5cb with SMTP id ffacd0b85a97d-42b3bfcde1bmr6451748f8f.51.1762880135650; Tue, 11 Nov 2025 08:55:35 -0800 (PST) Received: from [192.168.10.81] ([176.206.111.214]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-42abe63dfecsm29514102f8f.12.2025.11.11.08.55.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Nov 2025 08:55:31 -0800 (PST) Message-ID: <0de0215b-6013-4565-9cda-92a7b6f8c34b@redhat.com> Date: Tue, 11 Nov 2025 17:55:28 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v1 11/20] KVM: x86: Refactor opcode table lookup in instruction emulation To: "Chang S. Bae" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: seanjc@google.com, chao.gao@intel.com, zhao1.liu@intel.com References: <20251110180131.28264-1-chang.seok.bae@intel.com> <20251110180131.28264-12-chang.seok.bae@intel.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <20251110180131.28264-12-chang.seok.bae@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/10/25 19:01, Chang S. Bae wrote: > Refactor opcode lookup to clearly separate handling of different byte > sequences and prefix types, in preparation for REX2 support. > > The decoder begins with a one-byte opcode table by default and falls > through to other tables on escape bytes, but the logic is intertwined and > hard to extend. > > REX2 introduces a dedicated bit in its payload byte to indicate which > opcode table to use. To accommodate this mapping bit, the existing lookup > path needs to be restructured. > > No functional changes intended. > > Signed-off-by: Chang S. Bae > --- > arch/x86/kvm/emulate.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 763fbd139242..9c98843094a1 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -4773,7 +4773,6 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int > ctxt->_eip = ctxt->eip; > ctxt->fetch.ptr = ctxt->fetch.data; > ctxt->fetch.end = ctxt->fetch.data + insn_len; > - ctxt->opcode_len = 1; > ctxt->intercept = x86_intercept_none; > if (insn_len > 0) > memcpy(ctxt->fetch.data, insn, insn_len); > @@ -4877,20 +4876,24 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int > if (ctxt->rex.bits.w) > ctxt->op_bytes = 8; > > - /* Opcode byte(s). */ > - opcode = opcode_table[ctxt->b]; > - /* Two-byte opcode? */ > + /* Determine opcode byte(s): */ > if (ctxt->b == 0x0f) { > - ctxt->opcode_len = 2; > + /* Escape byte: start two-byte opcode sequence */ > ctxt->b = insn_fetch(u8, ctxt); > - opcode = twobyte_table[ctxt->b]; > - > - /* 0F_38 opcode map */ > if (ctxt->b == 0x38) { > + /* Three-byte opcode */ > ctxt->opcode_len = 3; > ctxt->b = insn_fetch(u8, ctxt); > opcode = opcode_map_0f_38[ctxt->b]; > + } else { > + /* Two-byte opcode */ > + ctxt->opcode_len = 2; > + opcode = twobyte_table[ctxt->b]; > } > + } else { > + /* Single-byte opcode */ > + ctxt->opcode_len = 1; > + opcode = opcode_table[ctxt->b]; > } > ctxt->d = opcode.flags; > This will also conflict with the VEX patches, overall I think all 10-12 patches can be merged in one. Paolo