Messages in this thread | | | Date | Fri, 12 Nov 2021 13:23:25 -0800 | Subject | Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support | From | Andy Lutomirski <> |
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On 11/12/21 13:16, Marc Orr wrote: >>> So cloud providers should have an interest to prevent such random stray >>> accesses if they wanna have guests. :) >> >> Yes, but IMO inducing a fault in the guest because of _host_ bug is wrong. > > I want to push back on "inducing a fault in the guest because of > _host_ bug is wrong.". The guest is _required_ to be robust against > the host maliciously (or accidentally) writing its memory. SNP > security depends on the guest detecting such writes. Therefore, why is > leveraging this system property that the guest will detect when its > private memory has been written wrong?
> > Especially when its orders or > magnitudes simpler than the alternative to have everything in the > system -- kernel, user-space, and guest -- all coordinate to agree > what's private and what's shared. Such a complex approach is likely to > bring a lot of bugs, vulnerabilities, and limitations on future design > into the picture. >
SEV-SNP, TDX, and any reasonable software solution all require that the host know which pages are private and which pages are shared. Sure, the old SEV-ES Linux host implementation was very simple, but it's nasty and fundamentally can't support migration.
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