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 52DF62DA75B; Fri, 13 Jun 2025 07:38:24 +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=1749800306; cv=none; b=D7Kw3bje2R1E6ueSfrewQQ3LGGxYU5vRrU2XmfnnT7Aw3ChRglC4CIOZWWuNSOioy3D52Qb4LNNG5PWz/MxgDtA7H++5YEdhU403WnPvf1CR2MNgAjRvh2T/JrSA1Bw8Fbg3y03oqinESB9v8W6CVfGCqh3UW7RnSi/HOtDOnw4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749800306; c=relaxed/simple; bh=w6Iij3cwmrMQPwKKuH03Kpq1oTsbrkREQC03eBxFJiM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qxQOcFSroyGej/IzU9FWMkn34HmrWuCUb7R9VQ5QN4e9DbKEaXmZRYXTEFDpNhXsXT8Q+8LChriBHYfl1FDss/2NiAEx2Q9EBZHRc2T0SARFCDDxJfqnZ4ae2MoDgQj0CghknFLQ/XDwijLJO8yPCT6gr6gPCMP9ThTad2rvi8k= ARC-Authentication-Results:i=1; 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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=xKz5uMPx52/eNlp0eiFTnJZNJrFbMI/rlNNtNSXShO8zJiTp0mAET+JVcHP+Wv8nN tLVo5f7HPHpPCQxOUor6oY0TNdqYfo0co2TiUmqze5EeoTzjiv+kvwmSnlcSHkrfER xkTa1hkIJqJY5vMFMD7XhgvJjkO8ObTde9aqkp0wEzHBJVSiuHiUT2Fypr2n9eDIG4 HRxa/+WRc9fZhBISxHTQ63MdtxTN/L8UNgM7lBE05kNgOTu9+vawYnqZoJbcXzfIB0 S9A7w81/OW86oO01xsR+plnYwA5EAAfyX0jzmm+R9E/5yswUdJpEJaw/dLSx+o76v6 xYFx81SS8BK7w== Message-ID: <457250dc-5e3f-498f-8b71-6ea4879f91af@zytor.com> Date: Fri, 13 Jun 2025 00:37:46 -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: [PATCH v1 0/3] x86/traps: Fix DR6/DR7 inintialization To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, seanjc@google.com, pbonzini@redhat.com, brgerst@gmail.com, tony.luck@intel.com, fenghuay@nvidia.com References: <20250613070118.3694407-1-xin@zytor.com> <20250613071842.GH2273038@noisy.programming.kicks-ass.net> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/13/2025 12:18 AM, Peter Zijlstra wrote: > On Fri, Jun 13, 2025 at 12:01:14AM -0700, Xin Li (Intel) wrote: >> >> Since only BLD-induced #DB exceptions clear DR6.BLD and other debug >> exceptions leave it unchanged, even if the first #DB is unrelated to >> BLD, DR6.BLD is still cleared. As a result, such a first #DB is >> misinterpreted as a BLD #DB, and a false warning is triggerred. >> >> >> Fix the bug by initializing DR6 by writing its architectural reset >> value at boot time. >> >> >> DR7 suffers from a similar issue. We apply the same fix. > > Bah, this DR6 polarity is a pain in the behind for sure. Patches look > good, except I'm really not a fan of using those 'names'. But I'll not > object too much of others like it. Let's see if there will be more objections :)