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

From: Philippe Mathieu-Daudé
Subject: Re: [RFC PATCH 11/12] hw/pci: Only allow PCI slave devices to write to direct memory
Date: Thu, 3 Sep 2020 15:18:53 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0

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

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