Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}
From: Dan Williams <hidden>
Date: 2021-08-24 01:06:04
Also in:
linux-arch, linux-doc, linux-mips, linux-pci, lkml, sparclinux, virtualization
On Mon, Aug 23, 2021 at 5:31 PM Kuppuswamy, Sathyanarayanan [off-list ref] wrote:
On 8/23/21 4:56 PM, Michael S. Tsirkin wrote:quoted
quoted
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<redacted> Signed-off-by: Kuppuswamy Sathyanarayanan<sathyanarayanan.kuppuswamy@linux.intel.com>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.