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

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