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 BD0BA210FB; Fri, 20 Jun 2025 22:53:15 +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=1750459999; cv=none; b=UDrAgdmgxieV/GphvxLZn48rxJE13NiJzbUGqT8hyJEgbiq4YlWh0QBDdL8msKY2B/jQNOkeXqaPxb3Xb7pDbColoIUlyhxTD09jyX9oSv87CWSGLWHAFXdwQHT1VtTxCm9bbYbD5iFYROcLZswxt4ILWSiDYi59aIlSiMnOMHc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750459999; c=relaxed/simple; bh=qfpCzB4wclc404l7tLJPX7+oneYlSYtlNEt/tGrUK3c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=q6D1RFgrdMe7OEwYk/C0CPgtr7y6khJ5gT4GhYh/ZkYVI4qnM5gwo47Mw7H23JHSYAPFcftyVhLuqFHVPSrteJxvaW70xTWhquYCS+gevbfKkuuqpbLTe+bhH10E50FZkDeyxra0Zd0Q3BLaVLISPy9v+9n5hhj5+N7xq+MKzy4= 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=QYAqO6y6; 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="QYAqO6y6" Received: from [IPV6:2601:646:8081:9482:8e69:eb66:369f:ca04] ([IPv6:2601:646:8081:9482:8e69:eb66:369f:ca04]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 55KMpi3J2670267 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Fri, 20 Jun 2025 15:51:44 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 55KMpi3J2670267 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025052101; t=1750459906; bh=dHs5e5KPRTLFRZrGk/aD2kqq/TN2P0Xy+dRkjImcTFE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=QYAqO6y6FGlEpC2XyzCDh3BoPOBHGwVPtkK5zpOUU7N+eppGdBi7v/I5Lxhdu8C4v RC+FM7W/vF/DaeY4RJvr4SW2D84Gj2X7BgiVqP5PLU3rk4mBFEMmMVOfWUL1NAE4nk 8HAd7qiejrsoP/0Gd73iRKMD9aZyVVNmvMlzztWl4wBD5JyCp5TBvAJNvigy65wghe Kf3pA4Ua2Mh+PStAxCtK2AEUfCT1j9cvB9sWLL7F341iJhl2iyTT9UPpyYFP/6dNvW rbBjZCMjhdqiBOTUQYRpupwqGFVBJtHQzLYPHQ9DpvzpGND4grxSQ8LwPsstBoxyr+ iBY+X4ocXC0BA== Message-ID: <7acedeba-9c90-403c-8985-0247981bf2b5@zytor.com> Date: Fri, 20 Jun 2025 15:51:38 -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 v7 02/10] x86/fred: Pass event data to the NMI entry point from KVM To: Sohil Mehta , Xin Li , x86@kernel.org, linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Peter Zijlstra , Sean Christopherson , Adrian Hunter , Kan Liang , Tony Luck , Zhang Rui , Steven Rostedt , Andrew Cooper , "Kirill A . Shutemov" , Jacob Pan , Andi Kleen , Kai Huang , Sandipan Das , linux-perf-users@vger.kernel.org, linux-edac@vger.kernel.org, kvm@vger.kernel.org, linux-pm@vger.kernel.org, linux-trace-kernel@vger.kernel.org References: <20250612214849.3950094-1-sohil.mehta@intel.com> <20250612214849.3950094-3-sohil.mehta@intel.com> <7525af7f-a817-47d5-91f7-d7702380c85f@zytor.com> <3281866f-2593-464d-a77e-5893b5e7014f@intel.com> <36374100-0587-47f1-9319-6333f6dfe4db@zytor.com> <39987c98-1f63-4a47-b15e-8c78f632da4e@intel.com> Content-Language: en-US From: "H. Peter Anvin" In-Reply-To: <39987c98-1f63-4a47-b15e-8c78f632da4e@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2025-06-19 15:57, Sohil Mehta wrote: > On 6/19/2025 3:45 PM, Xin Li wrote: >> On 6/19/2025 3:15 PM, Sohil Mehta wrote: >>> >>> I want to say that the event data for IRQ has to be zero until the >>> architecture changes — Similar to the /* Reserved, must be 0 */ comment >>> in asm_fred_entry_from_kvm(). >>> >> >> FRED spec says: >> >> For any other event, the event data are not currently defined and will >> be zero until they are. >> >> So "Event data not defined for IRQ thus 0." > > I am fine with this. Not *defined* removes the ambiguity. > So I was thinking about this, and wonder: how expensive is it to get the event data exit information out of VMX? If it is not very expensive, it would arguably be a good thing to future-proof by fetching that information, even if it is currently always zero. -hpa