linux-kernel - Re: [RFC v3 00/10] KVM PCIe/MSI passthrough on ARM/ARM64 and IOVA reserved regions

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Message-ID: <20161130103713.GB2724@arm.com>
Date:   Wed, 30 Nov 2016 10:37:14 +0000
From:   Will Deacon <will.deacon@....com>
To:     Auger Eric <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, christoffer.dall@...aro.org,
        marc.zyngier@....com, robin.murphy@....com,
        alex.williamson@...hat.com, joro@...tes.org, tglx@...utronix.de,
        jason@...edaemon.net, linux-arm-kernel@...ts.infradead.org,
        kvm@...r.kernel.org, drjones@...hat.com,
        linux-kernel@...r.kernel.org, pranav.sawargaonkar@...il.com,
        iommu@...ts.linux-foundation.org, punit.agrawal@....com,
        diana.craciun@....com
Subject: Re: [RFC v3 00/10] KVM PCIe/MSI passthrough on ARM/ARM64 and IOVA
 reserved regions

On Wed, Nov 30, 2016 at 10:49:33AM +0100, Auger Eric wrote:
> On 15/11/2016 14:09, Eric Auger wrote:
> > Following LPC discussions, we now report reserved regions through
> > iommu-group sysfs reserved_regions attribute file.
> > 
> > Reserved regions are populated through the IOMMU get_resv_region callback
> > (former get_dm_regions), now implemented by amd-iommu, intel-iommu and
> > arm-smmu.
> > 
> > The intel-iommu reports the [FEE0_0000h - FEF0_000h] MSI window as an
> > IOMMU_RESV_NOMAP reserved region.
> > 
> > arm-smmu reports the MSI window (arbitrarily located at 0x8000000 and
> > 1MB large) and the PCI host bridge windows.
> > 
> > The series integrates a not officially posted patch from Robin:
> > "iommu/dma: Allow MSI-only cookies".
> > 
> > This series currently does not address IRQ safety assessment.
> 
> I will respin this series taking into account Joerg's comment. Does
> anyone have additional comments or want to put forward some conceptual
> issues with the current direction and with this implementation?
> 
> As for the IRQ safety assessment, in a first step I would propose to
> remove the IOMMU_CAP_INTR_REMAP from arm-smmus and consider the
> assignment as unsafe. Any objection?

Well, yeah, because it's perfectly safe with GICv3.

Will