Re: [RFC PATCH 11/12] hw/pci: Only allow PCI slave devices to write to direct memory

[Philippe Mathieu-Daudé]

On 9/3/20 2:26 PM, Paolo Bonzini wrote:
> On 03/09/20 13:08, Philippe Mathieu-Daudé wrote:
>> Do not allow PCI slaves to write to indirect memory
>> regions such MMIO.
>>
>> This fixes LP#1886362 and LP#1888606.
> 
> What is a "PCI slave"?

TBH I at a quick look at the PCIe SPEC, but not PCI.
PCIe might be able to check the requester_id to check if the
access is valid, but I'm not sure where to add this check.

> Which devices would still be allowed to write?

As of this patch, all the non-PCI, but I plan to add a similar
check for USB on top of this series.

> I'm worried that there are cases of MMIO reads that would be broken.
> They are certainly niche these days, but they should still work; the
> most "famous" one is perhaps the old BASIC
> 
>    DEF SEG=&HB800
>    BLOAD "picture.pic", 0

This looks like ISA stuff. I don't think ISA does such checks
(and didn't plan to add them there) but I'd need to verify.

Do you have an acceptance test?

> 
> Paolo
>