linux-kernel - Re: Summary of LPC guest MSI discussion in Santa Fe

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Date:   Thu, 10 Nov 2016 15:52:00 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Auger Eric <eric.auger@...hat.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        Will Deacon <will.deacon@....com>, drjones@...hat.com,
        jason@...edaemon.net, kvm@...r.kernel.org, marc.zyngier@....com,
        benh@...nel.crashing.org, punit.agrawal@....com,
        linux-kernel@...r.kernel.org, arnd@...db.de, diana.craciun@....com,
        iommu@...ts.linux-foundation.org, pranav.sawargaonkar@...il.com,
        Don Dutile <ddutile@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, jcm@...hat.com,
        tglx@...utronix.de, robin.murphy@....com, dwmw@...zon.co.uk,
        Christoffer Dall <christoffer.dall@...aro.org>,
        eric.auger.pro@...il.com
Subject: Re: Summary of LPC guest MSI discussion in Santa Fe

On Thu, Nov 10, 2016 at 01:14:42AM +0100, Auger Eric wrote:
> Besides above problematic, I started to prototype the sysfs API. A first
> issue I face is the reserved regions become global to the iommu instead
> of characterizing the iommu_domain, ie. the "reserved_regions" attribute
> file sits below an iommu instance (~
> /sys/class/iommu/dmar0/intel-iommu/reserved_regions ||
> /sys/class/iommu/arm-smmu0/arm-smmu/reserved_regions).
> 
> MSI reserved window can be considered global to the IOMMU. However PCIe
> host bridge P2P regions rather are per iommu-domain.
> 
> Do you confirm the attribute file should contain both global reserved
> regions and all per iommu_domain reserved regions?
> 
> Thoughts?

This information is best attached to the sysfs-representation of
iommu-groups. The file should then contain the superset of all reserved
regions of the devices the group contains. This makes it usable later to
also describe RMRR/Unity-mapped regions on x86 there and make them
assignable to guests as well.


	Joerg