On 11.02.20 12:26, Will Deacon wrote: > On Mon, Feb 10, 2020 at 06:27:04PM +0100, Christian Borntraeger wrote: >> CC Marc Zyngier for KVM on ARM. Marc, see below. Will there be any >> use for this on KVM/ARM in the future? > > I can't speak for Marc, but I can say that we're interested in something > like this for potentially isolating VMs from a KVM host in Android. > However, we've currently been working on the assumption that the memory > removed from the host won't usually be touched by the host (i.e. no > KSM or swapping out), so all we'd probably want at the moment is to be > able to return an error back from arch_make_page_accessible(). Its return > code is ignored in this patch :/ > > One thing I don't grok about the ultravisor encryption is how it avoids > replay attacks when paging back in. For example, if the host is compromised > and replaces the page contents with an old encrypted value. Are you storing > per-page metadata somewhere to ensure "freshness" of the encrypted data? Cant talk about the others, but on s390 the ultravisor stores counter, tweak, address and hashing information. No replay or page exchange within the guest is possible. (We can move the guest content to a different host page though be using the export/import as this will revalidate the correctness from the guest point of view)
