Re: Regression with xhci console

[Jan Beulich <jbeulich@xxxxxxxx>]

On 11.03.2024 03:18, Marek Marczykowski-Górecki wrote:
> On Thu, Feb 01, 2024 at 06:01:56PM +0100, Roger Pau Monne wrote:
>> The current code that parses the IVMD blocks is relaxed with regard to the
>> restriction that such unity regions should always fall into memory ranges
>> marked as reserved in the memory map.
>>
>> However the type checks for the IVMD addresses are inverted, and as a result
>> IVMD ranges falling into RAM areas are accepted.  Note that having such 
>> ranges
>> in the first place is a firmware bug, as IVMD should always fall into 
>> reserved
>> ranges.
>>
>> Fixes: ed6c77ebf0c1 ('AMD/IOMMU: check / convert IVMD ranges for being / to 
>> be reserved')
>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> FYI Xen 4.17.3 with this patch (but not others in the series) causes
> panic on boot on Framework 14 AMD laptop:
> 
>     (XEN)  [0000000044570000, 000000005077efff] (usable)
>     ...
>     (XEN) AMD-Vi: Warning: IVMD: [4f83f000,4f880000) is not (entirely) in 
> reserved memory
>     (XEN) AMD-Vi: Error: IVMD: page at 4f83f000 can't be converted
>     ...
>     (XEN) Xen BUG at drivers/passthrough/amd/iommu_init.c:1386
> 
> Full boot log at https://github.com/QubesOS/qubes-issues/issues/9030
> 4.17.2 worked fine.
> I'll try the whole series (and the follow up one), but I don't expect
> any difference.
> 
> This looks to be related to XHCI console, which does use the same API to
> allow device to DMA into relevant buffers even when the rest of XHCI is
> used by dom0 (or even other domain if 'share=yes' is used):
> https://gitlab.com/xen-project/xen/-/blob/staging/xen/drivers/char/xhci-dbc.c?ref_type=heads#L1421-1424

Hmm, yes, this is what we get for allowing such (ab)use. I guess we need
to have iommu_add_extra_reserved_device_memory() actually convert the
region in question, to satisfy the later check. Care to make a patch?

Jan