Date: Thu, 10 Nov 2016 15:52:00 +0100
From: Joerg Roedel <joro@8bytes.org>
To: Auger Eric <eric.auger@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
        Will Deacon <will.deacon@arm.com>, drjones@redhat.com,
        jason@lakedaemon.net, kvm@vger.kernel.org, marc.zyngier@arm.com,
        benh@kernel.crashing.org, punit.agrawal@arm.com,
        linux-kernel@vger.kernel.org, arnd@arndb.de, diana.craciun@nxp.com,
        iommu@lists.linux-foundation.org, pranav.sawargaonkar@gmail.com,
        Don Dutile <ddutile@redhat.com>, linux-arm-kernel@lists.infradead.org,
        jcm@redhat.com, tglx@linutronix.de, robin.murphy@arm.com,
        dwmw@amazon.co.uk, Christoffer Dall <christoffer.dall@linaro.org>,
        eric.auger.pro@gmail.com
Subject: Re: Summary of LPC guest MSI discussion in Santa Fe
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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