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Subject: Re: [virtio-comment] RFC v2: virtio-hostmem: static, guest-owned memory regions
* Frank Yang (lfy@google.com) wrote: > +Christopher Dall who has tried to standardize goldfish before. > > Link: > https://github.com/741g/virtio-spec/blob/67602f232386a1782a35b9cb41087586ac3d19e2/virtio-hostmem.tex > > - Security model is pushed to the guest-specific layers like selinux; it is > possible (and this is useful) for a physical page to be shared across guest > processes, and it is up to the guest's current security model to enforce > malicious apps not having access. I'm not quite sure I understand this or the statement: Indeed, it is possible for a malicious guest process to improperly access the shared memory of a gralloc/ashmem/dmabuf implementation on virtio-hostmem, but we regard that as a flaw in the security model of the guest, not the security model of virtio-hostmem. what's the limit of 'improperly access'. If that means that it calls/corrupts/breaks the guest that's fine - if it could DMA over the host VMM that's not as nice. I'm also a bit confused by your enumeration/probing. You say that the host can refuse a request for a particular CODEC type; that's fine if it hasn't got it - but can a guest get a list of what the host supports? (Is that what the 'Device configuration layout' is about or is that about the subdevices you already have mapped?) I don't understand the: When the guest starts up, regardless of whether it is plugged in, memory regions for each sub-device will be reserved. When the hostmem device is plugged in via PCI, instance creation/destruction and message sending is allowed. Otherwise all operations fail with a guest specific error code. Say you support hundreds of different codecs - what happens? I also don't understand what happens before plugging. (Somewhere near the bottom is the typo notificationotification ) Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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