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

[Andi Kleen]

On 8/24/2021 1:31 PM, Bjorn Helgaas wrote:
> On Tue, Aug 24, 2021 at 01:14:02PM -0700, Andi Kleen wrote:
> > On 8/24/2021 11:55 AM, Bjorn Helgaas wrote:
> > > [+cc Rajat; I still don't know what "shared memory with a hypervisor
> > > in a confidential guest" means,
> > A confidential guest is a guest which uses memory encryption to isolate
> > itself from the host. It doesn't trust the host. But it still needs to
> > communicate with the host for IO, so it has some special memory areas that
> > are explicitly marked shared. These are used to do IO with the host. All
> > their usage needs to be carefully hardened to avoid any security attacks on
> > the guest, that's why we want to limit this interaction only to a small set
> > of hardened drivers. For MMIO, the set is currently only virtio and MSI-X.
> Good material for the commit log next time around.  Thanks!

This is all in the patch intro too, which should make it into the merge 
commits.

I don't think we can reexplain the basic concepts for every individual 
patch in a large patch kit.


-Andi