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Wed, 21 Apr 2021 08:09:13 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3A17011C04C; Wed, 21 Apr 2021 08:09:13 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.171.39.90]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 21 Apr 2021 08:09:13 +0000 (GMT) Subject: Re: [PATCH v3 9/9] KVM: Move instrumentation-safe annotations for enter/exit to x86 code To: Sean Christopherson , Paolo Bonzini Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Michael Tokarev , Sven Schnelle , Heiko Carstens References: <20210415222106.1643837-1-seanjc@google.com> <20210415222106.1643837-10-seanjc@google.com> From: Christian Borntraeger Message-ID: <0c74158d-279a-5afa-0778-822c77ac8dc2@de.ibm.com> Date: Wed, 21 Apr 2021 10:09:11 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <20210415222106.1643837-10-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: O0Gbqj7PsH1bpmljgRZ33Sx1MRyz_OsV X-Proofpoint-GUID: QYIWjy8vpv4N55O6Q4tlpQ0Nqt1_mssd X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-04-21_02:2021-04-21,2021-04-21 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 lowpriorityscore=0 phishscore=0 impostorscore=0 priorityscore=1501 mlxscore=0 clxscore=1015 malwarescore=0 suspectscore=0 spamscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104210063 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16.04.21 00:21, Sean Christopherson wrote: > Drop the instrumentation_{begin,end}() annonations from the common KVM > guest enter/exit helpers, and massage the x86 code as needed to preserve > the necessary annotations. x86 is the only architecture whose transition > flow is tagged as noinstr, and more specifically, it is the only > architecture for which instrumentation_{begin,end}() can be non-empty. > > No other architecture supports CONFIG_STACK_VALIDATION=y, and s390 is the > only other architecture that support CONFIG_DEBUG_ENTRY=y. For > instrumentation annontations to be meaningful, both aformentioned configs > must be enabled. > > Letting x86 deal with the annotations avoids unnecessary nops by > squashing back-to-back instrumention-safe sequences. We have considered implementing objtool for s390. Not sure where we stand and if we will do this or not. Sven/Heiko? So maybe drop this patch until every other arch agrees that there are no plans to implement this.