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X-CSE-ConnectionGUID: jTd0ltwbQgqQpZBavv0KNQ== X-CSE-MsgGUID: gsrHt0IRRCO6jjXAu+Z/wQ== X-IronPort-AV: E=McAfee;i="6800,10657,11786"; a="102414240" X-IronPort-AV: E=Sophos;i="6.23,235,1770624000"; d="scan'208";a="102414240" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 May 2026 12:55:46 -0700 X-CSE-ConnectionGUID: hAplbd1gQkqT8VVXTxpuug== X-CSE-MsgGUID: Hrxx/nEARv6BRs/MFvyzIg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,235,1770624000"; d="scan'208";a="276558392" Received: from gabaabhi-mobl2.amr.corp.intel.com (HELO [10.125.108.103]) ([10.125.108.103]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 May 2026 12:55:45 -0700 Message-ID: <34cb5030-c62a-404b-b801-972840bb230b@intel.com> Date: Thu, 14 May 2026 12:55:45 -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] x86/entry: Read CR2 in asm entry stub to redcue NMI clobbering window To: Andrew Cooper Cc: bp@alien8.de, dave.hansen@linux.intel.com, kernel-team@meta.com, linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com, riel@surriel.com, tglx@kernel.org, x86@kernel.org, xin@zytor.com References: <669f925a-df4f-4497-ae41-46b08b6abce6@intel.com> Content-Language: en-US From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/14/26 12:49, Andrew Cooper wrote: > Really, the NMI handler needs to preserve the registers it potentially > clobbers, and that still requires the NMI handler doing it in assembly > before entering C. Yup, totally agree. It's not rocket science, and it's what we do for CR3 because of PTI, but it's also no fun. So I didn't want to suggest it. I mean, we've lived with this behavior _forever_, right? So how bad could it be?