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Wed, 18 Nov 2020 07:06:41 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0AI6tIJI166456; Wed, 18 Nov 2020 07:06:41 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3020.oracle.com with ESMTP id 34umd076rk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 18 Nov 2020 07:06:40 +0000 Received: from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 0AI76RxM012749; Wed, 18 Nov 2020 07:06:31 GMT Received: from linux.home (/92.157.91.83) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 17 Nov 2020 23:06:27 -0800 Subject: Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code To: Borislav Petkov Cc: tglx@linutronix.de, mingo@redhat.com, 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, 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: <20201116144757.1920077-1-alexandre.chartre@oracle.com> <20201116201711.GE1131@zn.tnic> <44a88648-738a-4a4b-9c25-6b70000e037c@oracle.com> <20201117165539.GG5719@zn.tnic> <890f6b7e-a268-2257-edcb-5eacc7db3d8e@oracle.com> <20201117182809.GK5719@zn.tnic> <33a1c6ee-0122-0b0c-ed2d-1578b29ef7c1@oracle.com> <20201117212307.GR5719@zn.tnic> From: Alexandre Chartre Message-ID: <1c39ebd0-2afd-5f51-ef48-ea3f378d8a0d@oracle.com> Date: Wed, 18 Nov 2020 08:08:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201117212307.GR5719@zn.tnic> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9808 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxscore=0 phishscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011180047 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9808 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 suspectscore=0 malwarescore=0 bulkscore=0 impostorscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 mlxscore=0 priorityscore=1501 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011180047 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/17/20 10:23 PM, Borislav Petkov wrote: > On Tue, Nov 17, 2020 at 08:02:51PM +0100, Alexandre Chartre wrote: >> No. This prevents the guest VM from gathering data from the host >> kernel on the same cpu-thread. But there's no mitigation for a guest >> VM running on a cpu-thread attacking another cpu-thread (which can be >> running another guest VM or the host kernel) from the same cpu-core. >> You cannot use flush/clear barriers because the two cpu-threads are >> running in parallel. > > Now there's your justification for why you're doing this. It took a > while... > > The "why" should always be part of the 0th message to provide > reviewers/maintainers with answers to the question, what this pile of > patches is all about. Please always add this rationale to your patchset > in the future. > Sorry about that, I will definitively try to do better next time. :-} Thanks, alex.