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Mon, 28 Sep 2020 09:21:01 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D88B94C058; Mon, 28 Sep 2020 09:21:00 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.145.36.223]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 28 Sep 2020 09:21:00 +0000 (GMT) Subject: Re: [RFC Patch 0/2] KVM: SVM: Cgroup support for SVM SEV ASIDs To: Janosch Frank , Paolo Bonzini , Sean Christopherson , Vipin Sharma Cc: thomas.lendacky@amd.com, tj@kernel.org, lizefan@huawei.com, joro@8bytes.org, corbet@lwn.net, brijesh.singh@amd.com, jon.grimm@amd.com, eric.vantassell@amd.com, gingell@google.com, rientjes@google.com, kvm@vger.kernel.org, x86@kernel.org, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, "kvm-ppc@vger.kernel.org" , linux-s390 , Paul Mackerras References: <20200922004024.3699923-1-vipinsh@google.com> <20200922014836.GA26507@linux.intel.com> <45117fcc-d6b8-fab9-11dc-79181058ed62@redhat.com> From: Christian Borntraeger Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-28_07:2020-09-24,2020-09-28 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 lowpriorityscore=0 clxscore=1011 impostorscore=0 malwarescore=0 adultscore=0 priorityscore=1501 suspectscore=0 mlxlogscore=999 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009280076 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28.09.20 11:12, Janosch Frank wrote: > On 9/23/20 2:47 PM, Paolo Bonzini wrote: >> On 22/09/20 03:48, Sean Christopherson wrote: >>> This should be genericized to not be SEV specific. TDX has a similar >>> scarcity issue in the form of key IDs, which IIUC are analogous to SEV ASIDs >>> (gave myself a quick crash course on SEV ASIDs). Functionally, I doubt it >>> would change anything, I think it'd just be a bunch of renaming. The hardest >>> part would probably be figuring out a name :-). >>> >>> Another idea would be to go even more generic and implement a KVM cgroup >>> that accounts the number of VMs of a particular type, e.g. legacy, SEV, >>> SEV-ES?, and TDX. That has potential future problems though as it falls >>> apart if hardware every supports 1:MANY VMs:KEYS, or if there is a need to >>> account keys outside of KVM, e.g. if MKTME for non-KVM cases ever sees the >>> light of day. >> >> Or also MANY:1 (we are thinking of having multiple VMs share the same >> SEV ASID). >> >> It might even be the same on s390 and PPC, in which case we probably >> want to implement this in virt/kvm. Paul, Janosch, do you think this >> would make sense for you? The original commit message is below. >> >> Paolo >> >>> On Mon, Sep 21, 2020 at 05:40:22PM -0700, Vipin Sharma wrote: >>>> Hello, >>>> >>>> This patch series adds a new SEV controller for tracking and limiting >>>> the usage of SEV ASIDs on the AMD SVM platform. >>>> >>>> SEV ASIDs are used in creating encrypted VM and lightweight sandboxes >>>> but this resource is in very limited quantity on a host. >>>> >>>> This limited quantity creates issues like SEV ASID starvation and >>>> unoptimized scheduling in the cloud infrastructure. >>>> >>>> SEV controller provides SEV ASID tracking and resource control >>>> mechanisms. >> > > On s390 we currently support a few million protected guests per LPAR so > guest IDs are not exactly scarce. However having accounting for them > might add some value nevertheless, especially when having large amount > of protected containers. > > @Christian: Any thoughts on this? Yes, maybe it is a good idea to limit containers to only have a sane number of secure guests, so that a malicious pod cannot consume all IDs by calling CREATE_VM and KVM_PV_ENABLE million times or so.