On Mon, Jun 22, 2020 at 04:27:28PM +0200, Christian Borntraeger wrote: > On 19.06.20 04:05, David Gibson wrote: > > A number of hardware platforms are implementing mechanisms whereby the > > hypervisor does not have unfettered access to guest memory, in order > > to mitigate the security impact of a compromised hypervisor. > > > > AMD's SEV implements this with in-cpu memory encryption, and Intel has > > its own memory encryption mechanism. POWER has an upcoming mechanism > > to accomplish this in a different way, using a new memory protection > > level plus a small trusted ultravisor. s390 also has a protected > > execution environment. > > > > The current code (committed or draft) for these features has each > > platform's version configured entirely differently. That doesn't seem > > ideal for users, or particularly for management layers. > > > > AMD SEV introduces a notionally generic machine option > > "machine-encryption", but it doesn't actually cover any cases other > > than SEV. > > > > This series is a proposal to at least partially unify configuration > > for these mechanisms, by renaming and generalizing AMD's > > "memory-encryption" property. It is replaced by a > > "host-trust-limitation" property pointing to a platform specific > > object which configures and manages the specific details. > > > > For now this series covers just AMD SEV and POWER PEF. I'm hoping it > > can be extended to cover the Intel and s390 mechanisms as well, > > though. > > Let me try to summarize what I understand what you try to achieve: > one command line parameter for all platforms that > > common across all platforms: > - disable KSM > - by default enables iommu_platform Pretty much, yes. Plus, in future if we discover other things that don't make sense in the context of a guest whose memory we can't freely access, it can check for those and set sane defaults accordingly. > per platform: > - setup the necessary encryption scheme when appropriate > - block migration That's true for now, but I believe there are plans to make secure guests migratable, so that's not an inherent property. > -.... > > > The tricky part is certainly the per platform thing. For example on > s390 we just have a cpumodel flag that provides interfaces to the guest > to switch into protected mode via the ultravisor. This works perfectly > fine with the host model, so no need to configure anything. The platform > code then disables KSM _on_switchover_ and not in general. Right, because your platform code is aware of the switchover. On POWER, we aren't. > Because the > guest CAN switch into protected, but it does not have to. > > So this feels really hard to do right. Would a virtual BoF on KVM forum > be too late? We had a BoF on protected guests last year and that was > valuable. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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