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[23.128.96.18]) by mx.google.com with ESMTP id y10si7535442ejf.165.2020.11.09.11.37.17; Mon, 09 Nov 2020 11:37:42 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730017AbgKITfx (ORCPT + 99 others); Mon, 9 Nov 2020 14:35:53 -0500 Received: from mga06.intel.com ([134.134.136.31]:59494 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729499AbgKITfx (ORCPT ); Mon, 9 Nov 2020 14:35:53 -0500 IronPort-SDR: osQXlg75rveg2htfBSuBNQwMiVBTqj4f3MgOMZPR5iI/qNo9pEY3eQdaBN9pba5BzpvV9H3eYN PJgZllONypAA== X-IronPort-AV: E=McAfee;i="6000,8403,9800"; a="231489063" X-IronPort-AV: E=Sophos;i="5.77,464,1596524400"; d="scan'208";a="231489063" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Nov 2020 11:35:52 -0800 IronPort-SDR: wnUsVxu9jT7ZOAHatQU60EeWi0qqzOMYy0kYCEHHNvJehOmm9IRvMByAb5ROq+5TR/DtFuF/6h q1O3eR80EWHg== X-IronPort-AV: E=Sophos;i="5.77,464,1596524400"; d="scan'208";a="428116887" Received: from gberger1-mobl2.ger.corp.intel.com (HELO [10.209.33.167]) ([10.209.33.167]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Nov 2020 11:35:51 -0800 Subject: Re: [RFC][PATCH 00/24] x86/pti: Defer CR3 switch to C code To: Alexandre Chartre , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, thomas.lendacky@amd.com, jroedel@suse.de Cc: konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, junaids@google.com, oweisse@google.com, rppt@linux.vnet.ibm.com, graf@amazon.de, mgross@linux.intel.com, kuzuno@gmail.com References: <20201109144425.270789-1-alexandre.chartre@oracle.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201109144425.270789-1-alexandre.chartre@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/9/20 6:44 AM, Alexandre Chartre wrote: > - map more syscall, interrupt and exception entry code into the user > page-table (map all noinstr code); This seems like the thing we'd want to tag explicitly rather than make it implicit with 'noinstr' code. Worst-case, shouldn't this be: #define __entry_func noinstr or something? I'd also like to see a lot more discussion about what the rules are for the C code and the compiler. We can't, for instance, do a normal printk() in this entry functions. Should we stick them in a special section and have objtool look for suspect patterns or references? I'm most worried about things like this: if (something_weird) pr_warn("this will oops the kernel\n");