On Thu, Sep 24, 2020 at 1:55 PM Tom Lendacky <thomas.lendacky@xxxxxxx> wrote: > > On 9/24/20 2:21 PM, Sean Christopherson wrote: > > On Tue, Sep 22, 2020 at 02:14:04PM -0700, Vipin Sharma wrote: > >> On Mon, Sep 21, 2020 at 06:48:38PM -0700, Sean Christopherson wrote: > >>> 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. > >>> > >>> 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. > >> > >> I read about the TDX and its use of the KeyID for encrypting VMs. TDX > >> has two kinds of KeyIDs private and shared. > > > > To clarify, "shared" KeyIDs are simply legacy MKTME KeyIDs. This is relevant > > because those KeyIDs can be used without TDX or KVM in the picture. > > > >> On AMD platform there are two types of ASIDs for encryption. > >> 1. SEV ASID - Normal runtime guest memory encryption. > >> 2. SEV-ES ASID - Extends SEV ASID by adding register state encryption with > >> integrity. > >> > >> Both types of ASIDs have their own maximum value which is provisioned in > >> the firmware > > > > Ugh, I missed that detail in the SEV-ES RFC. Does SNP add another ASID type, > > or does it reuse SEV-ES ASIDs? If it does add another type, is that trend > > expected to continue, i.e. will SEV end up with SEV, SEV-ES, SEV-ES-SNP, > > SEV-ES-SNP-X, SEV-ES-SNP-X-Y, etc...? > > SEV-SNP and SEV-ES share the same ASID range. Where is this documented? From the SEV-SNP FW ABI Spec 0.8 "The firmware checks that ASID is an encryption capable ASID. If not, the firmware returns INVALID_ASID." that doesn't seem clear that an SEV-ES ASID is required. Should this document be more clear?
