From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 C0B41304BDE for ; Fri, 15 Aug 2025 17:15:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755278121; cv=none; b=V6uCQQaPyKspdc5yjNDsJlyptAqriXj9E1HdYVwfZVV0rZZoNXa5whmbnfAe+bb98mvSWUoD3Nqbg0Lk59x31A4JttWUu9h9V/ftlsuPE6HnLqZYOVzGKDmkCaHP3+psuJvyYmu6lHOe8rTWgR+YYBpyv4sTnhxtx2/c/62I3Zw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755278121; c=relaxed/simple; bh=Q9VDTyPsJ1nrsJ9IPGQ/uH24LWZk1d50M/ALSVgVhkY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=F5dblKPwqI8Ff79Nw9yXgKBj6KaGwv6A1WDNuhREkl7xgW5yhRjtQedLHCT2EbhO/hpz/b1tnSAH2nhQ42aNTSZg4qeRJhgq7+XeqkTx7+MIGgyQt/lpqwaAaSGXpQT6sY1H0lp2B1QLFgTgUbXEasOdE8EBJRg885R3MUSnPzQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=PUMPiO8R; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="PUMPiO8R" Received: from [IPV6:2601:646:8081:9484:50f9:ca46:26fb:a765] ([IPv6:2601:646:8081:9484:50f9:ca46:26fb:a765]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 57FHF2ON2012703 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Fri, 15 Aug 2025 10:15:03 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 57FHF2ON2012703 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025072201; t=1755278104; bh=xMvjS3Kd5v0VRPHOeHrYngN+OKw4RRNU/wrppPGKZ7U=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=PUMPiO8RbYAmd3BO2Gb40KMQ8esEioA/r32CoRljiSql0GrlTlOWkDSmcN6ovbTQ0 tutde6nkhOHwTobfcv8Sj3JmiahVAE32ToleR2IGuDLMfjJRPv41Clitk5yTmmgkWV jn6W7JHygJLtyukV9UcuzPML0k0iN7fdLkcx362GnbKToeVNx7hueYavitqNVEljLM mIiNbcFqyz1UsiCDI6yXge1Cq9xYzobj21GRjYHq29wT0zwmOLaodQHsFfL33jbsyi WbT05zyCsHz68/o56kaDqmBUZSYJfANueAwexY3+IpZGb7pjNRKJ1ili9j+gxnGbJL LkXgkBjXrpdUQ== Message-ID: <78bd985a-a59e-4469-a84d-a0eb7faa20c3@zytor.com> Date: Fri, 15 Aug 2025 10:14:57 -0700 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: [RFC][PATCH] x86,ibt: Use UDB instead of 0xEA To: Andrew Cooper , Peter Zijlstra Cc: x86@kernel.org, kees@kernel.org, alyssa.milburn@intel.com, scott.d.constable@intel.com, joao@overdrivepizza.com, samitolvanen@google.com, nathan@kernel.org, alexei.starovoitov@gmail.com, mhiramat@kernel.org, ojeda@kernel.org, linux-kernel@vger.kernel.org References: <20250814111732.GW4067720@noisy.programming.kicks-ass.net> <2c121572-8fde-4288-80ca-ab79f2b22cce@zytor.com> <20250815074939.GA3419281@noisy.programming.kicks-ass.net> <20250815102839.GD4068168@noisy.programming.kicks-ass.net> <20250815103055.GE4068168@noisy.programming.kicks-ass.net> <20250815105908.GB3245006@noisy.programming.kicks-ass.net> <055f4c2b-0e7f-44ae-92ff-a1025a217208@citrix.com> Content-Language: en-US From: "H. Peter Anvin" In-Reply-To: <055f4c2b-0e7f-44ae-92ff-a1025a217208@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 2025-08-15 04:19, Andrew Cooper wrote: >> >> CS Jcc, decodes to Jcc,pn for non-taken >> DS Jcc, decodes to Jcc,pt for taken > > Ah, thanks.  I was looking at the hex in one of the comments and still > couldn't figure it out. > > So with this notation, we also have the dual meaning of ,pt between the > P4 and LNC.  At least the encoding is the same. > What "dual meaning?" -hpa