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 34F592F5301; Wed, 18 Jun 2025 00:43:25 +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=1750207407; cv=none; b=HIaOIlNrHExbUoCENy97pgGLslIe7733XsnxO1arqifr6ZzjxBVlJwLT3BrQjojF+LIhx4YPI6hWeXavwB9i9hJG1w+/ky9XHkK8PHPWXT8tnLtSCBgHoQfseL/cah7O24q+EbYuMLhul+CE88f9VMYP6R3FgC/AKC26uVxFfvY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750207407; c=relaxed/simple; bh=ZyP0kbMtcCQ83BQxcvLLk9BQpHXtlcVBp/dgcpPHwws=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=WZWo+SulSfnoLg+EqR2RNUvzBRqY4hRdQZovieWFG8r0fQ+ovWYQ7kMkTeJJ70kfqTo4eyi9t0c7p+bYPlu65HqHgwuzHySl9bNjDo0VeZ7hXKfCDSoqYS8I7v9zCfJYIw2dDyliJ0KIvImGX6PA4eXoC7d/hV/w4OxvonKv+1w= ARC-Authentication-Results:i=1; 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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=kIn06OAdLFu/YMgz/MfjKZ5P6dUCfyFL6LpMBtYancCXkQvUYLmQIoucTmc9/jQhI uGpv6dgKe8MzOR2dVu9KI2tvfp1BFtHiV4hbYZ9wCF91zlweOtQy38e2PT2NvFtTQA YGvfzL86cgQIglc05axDOzfRC8acmp1dGm30MYRLx/d+Ke2gPtRwFrhbW9//v9wKtT QTWfej7CXam8ZK+y+nz7ripRlRh1R5Bk+nvXib+0pdF/zaio9sbsqzpZ3ewsVDNu4z igFIrfV+ib2/cMq+MXfnfsxsuxFfyOZqpe9xB7/Dh0sRT8CREIgEpSmCdmVckpJGHi AVC6pxH+9YkhA== Message-ID: Date: Tue, 17 Jun 2025 17:42:51 -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 v2 1/2] x86/traps: Initialize DR6 by writing its architectural reset value To: Sohil Mehta , Sean Christopherson 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, pbonzini@redhat.com, peterz@infradead.org, brgerst@gmail.com, tony.luck@intel.com, fenghuay@nvidia.com References: <20250617073234.1020644-1-xin@zytor.com> <20250617073234.1020644-2-xin@zytor.com> <276d66a1-dafe-4ed8-aefd-8f60e34ff575@intel.com> 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 6/17/2025 4:10 PM, Sohil Mehta wrote: >> Ah, and now I see that DR6_RESERVED is an existing #define in a uAPI header (Xin >> said there were a few, but I somehow missed them earlier). Maybe just leave that >> thing alone, but update the comment to state that it's a historical wart? And >> then put DR6_ACTIVE_LOW and other macros in arch/x86/include/asm/debugreg.h? >> > Yeah, that's unfortunate. Updating the comment seems the best we do for now. It's a mess, and I don't think I can just remove DR6_RESERVED. But the value 0xFFFF0FF0 no longer makes sense on newer CPUs, so maybe it won't cause any real problem?