# Re: \[PATCH v4 11/15\] pci: Add pci\_iomap\_shared{,\_range}

- From: Kuppuswamy, Sathyanarayanan \<sathyanarayanan.kuppuswamy@linux.intel.com\>
- Date: 2021-08-24 00:31:03 
- List: linux-mips
- Page: https://ratatoskr.run/linux-mips/2021/08/1486336
- Thread: https://ratatoskr.run/linux-pci/2021/08/1468282/t.md

```text


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<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.

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
```