Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}

[Kuppuswamy, Sathyanarayanan]

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.

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer