linux-kernel - Re: [PATCH 0/2] iommu/vt-d: Select PCI_PRI for INTEL_IOMMU_SVM

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Date:   Wed, 9 Oct 2019 16:50:09 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Keith Busch <keith.busch@...el.com>,
        iommu@...ts.linux-foundation.org,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 0/2] iommu/vt-d: Select PCI_PRI for INTEL_IOMMU_SVM

On Wed Oct 09 19, Bjorn Helgaas wrote:
>From: Bjorn Helgaas <bhelgaas@...gle.com>
>
>I think intel-iommu.c depends on CONFIG_AMD_IOMMU in an undesirable way:
>
>When CONFIG_INTEL_IOMMU_SVM=y, iommu_enable_dev_iotlb() calls PRI
>interfaces (pci_reset_pri() and pci_enable_pri()), but those are only
>implemented when CONFIG_PCI_PRI is enabled.  If CONFIG_PCI_PRI is not
>enabled, there are stubs that just return failure.
>
>The INTEL_IOMMU_SVM Kconfig does nothing with PCI_PRI, but AMD_IOMMU
>selects PCI_PRI.  So if AMD_IOMMU is enabled, intel-iommu.c gets the full
>PRI interfaces.  If AMD_IOMMU is not enabled, it gets the PRI stubs.
>
>This seems wrong.  The first patch here makes INTEL_IOMMU_SVM select
>PCI_PRI so intel-iommu.c always gets the full PRI interfaces.
>
>The second patch moves pci_prg_resp_pasid_required(), which simply returns
>a bit from the PCI capability, from #ifdef CONFIG_PCI_PASID to #ifdef
>CONFIG_PCI_PRI.  This is related because INTEL_IOMMU_SVM already *does*
>select PCI_PASID, so it previously always got pci_prg_resp_pasid_required()
>even though it got stubs for other PRI things.
>
>Since these are related and I have several follow-on ATS-related patches in
>the queue, I'd like to take these both via the PCI tree.
>
>Bjorn Helgaas (2):
>  iommu/vt-d: Select PCI_PRI for INTEL_IOMMU_SVM
>  PCI/ATS: Move pci_prg_resp_pasid_required() to CONFIG_PCI_PRI
>
> drivers/iommu/Kconfig   |  1 +
> drivers/pci/ats.c       | 55 +++++++++++++++++++----------------------
> include/linux/pci-ats.h | 11 ++++-----
> 3 files changed, 31 insertions(+), 36 deletions(-)
>
>-- 
>2.23.0.581.g78d2f28ef7-goog
>
>_______________________________________________
>iommu mailing list
>iommu@...ts.linux-foundation.org
>https://lists.linuxfoundation.org/mailman/listinfo/iommu

Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>

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