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

From: "Radovanovic, Aleksandar" <aleksandar.radovanovic@amd.com>
To: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
	"Gupta, Nipun" <Nipun.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
Date: Fri, 14 Oct 2022 12:13:45 +0000	[thread overview]
Message-ID: <MN2PR12MB43583BB73731986D15B3620789249@MN2PR12MB4358.namprd12.prod.outlook.com> (raw)
In-Reply-To: <Y0lODVFsp4KMfPdu@kroah.com>

[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
> <robin.murphy@arm.com>; robh+dt@kernel.org;
> krzysztof.kozlowski+dt@linaro.org; rafael@kernel.org;
> eric.auger@redhat.com; alex.williamson@redhat.com; cohuck@redhat.com;
> Gupta, Puneet (DCG-ENG) <puneet.gupta@amd.com>;
> song.bao.hua@hisilicon.com; mchehab+huawei@kernel.org;
> f.fainelli@gmail.com; jeffrey.l.hugo@gmail.com; saravanak@google.com;
> Michael.Srba@seznam.cz; mani@kernel.org; yishaih@nvidia.com;
> will@kernel.org; joro@8bytes.org; masahiroy@kernel.org;
> ndesaulniers@google.com; linux-arm-kernel@lists.infradead.org; linux-
> kbuild@vger.kernel.org; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org; kvm@vger.kernel.org; okaya@kernel.org;
> Anand, Harpreet <harpreet.anand@amd.com>; Agarwal, Nikhil
> <nikhil.agarwal@amd.com>; Simek, Michal <michal.simek@amd.com>; git
> (AMD-Xilinx) <git@amd.com>
> Subject: Re: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its
> domain as parent
> 
> Caution: This message originated from an External Source. Use proper
> caution when opening attachments, clicking links, or responding.
> 
> 
> 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