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

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Message-ID: <20191015214003.GA178213@google.com>
Date:   Tue, 15 Oct 2019 16:40:03 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>
Cc:     Ashok Raj <ashok.raj@...el.com>,
        Keith Busch <keith.busch@...el.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Jerry Snitselaar <jsnitsel@...hat.com>
Subject: Re: [PATCH 0/2] iommu/vt-d: Select PCI_PRI for INTEL_IOMMU_SVM

[+cc Jerry]

On Wed, Oct 09, 2019 at 05:45:49PM -0500, 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(-)

I applied these to pci/virtualization for v5.5 with Kuppuswamy's
and Joerg's Reviewed-by on both and Jerry's on the first.  Thank you
all for checking this over!