On Mon, Aug 23, 2021 at 5:31 PM Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote: > > > > On 8/23/21 4:56 PM, Michael S. Tsirkin wrote: > >> Add a new variant of pci_iomap for mapping all PCI resources > >> of a devices as shared memory with a hypervisor in a confidential > >> guest. > >> > >> Signed-off-by: Andi Kleen<ak@xxxxxxxxxxxxxxx> > >> Signed-off-by: Kuppuswamy Sathyanarayanan<sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > > I'm a bit puzzled by this part. So why should the guest*not* map > > pci memory as shared? And if the answer is never (as it seems to be) > > then why not just make regular pci_iomap DTRT? > > It is in the context of confidential guest (where VMM is un-trusted). So > we don't want to make all PCI resource as shared. It should be allowed > only for hardened drivers/devices. That's confusing, isn't device authorization what keeps unaudited drivers from loading against untrusted devices? I'm feeling like Michael that this should be a detail that drivers need not care about explicitly, in which case it does not need to be exported because the detail can be buried in lower levels. Note, I specifically said "unaudited", not "hardened" because as Greg mentioned the kernel must trust drivers, its devices that may not be trusted.
