RE: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its domain as parent

Radovanovic, Aleksandar
2022-10-14T12:14:12Z

[AMD Official Use Only - General]

> -----Original Message-----
> From: gregkh@linuxfoundation.org <gregkh@linuxfoundation.org>
> Sent: 14 October 2022 12:55
> To: Radovanovic, Aleksandar <aleksandar.radovanovic@amd.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>; Gupta, Nipun
> <Nipun.Gupta@amd.com>; Marc Zyngier <maz@kernel.org>; Robin Murphy
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> Gupta, Puneet (DCG-ENG) <puneet.gupta@amd.com>;
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> Subject: Re: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its
> domain as parent
>
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>
> On Fri, Oct 14, 2022 at 11:18:36AM +0000, Radovanovic, Aleksandar wrote:
> > Anyway, I think we're straying off topic here, none of this is visible to the
> kernel anyway. The question that we still need to answer is, are you OK with
> the limitations I listed originally?
>
> What original limitations?

Limitations with regards to MSI message configuration of a CDX device:

1) MSI write value is at most 16 useable bits

2) MSI address value must be the same across all vectors of a single CDX device
This would be the (potentially IOMMU translated) I/O address of
GITS_TRANSLATER. As long as that IOMMU translation is consistent across a
single device, I think we should be OK.

> This thread is crazy and complex and you need to
> use your \n key more :)

I do try, but the corporate mail client that we're stuck with seems to just merge
everything back together. Sigh.

> thanks,
>
> greg k-h