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

From: Bjorn Helgaas <helgaas@kernel.org>
To: Kuppuswamy Sathyanarayanan
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Joerg Roedel <joro@8bytes.org>
Cc: Ashok Raj <ashok.raj@intel.com>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	Keith Busch <keith.busch@intel.com>,
	iommu@lists.linux-foundation.org
Subject: Re: [PATCH 0/2] iommu/vt-d: Select PCI_PRI for INTEL_IOMMU_SVM
Date: Tue, 15 Oct 2019 16:40:03 -0500	[thread overview]
Message-ID: <20191015214003.GA178213@google.com> (raw)
In-Reply-To: <20191009224551.179497-1-helgaas@kernel.org>

[+cc Jerry]

On Wed, Oct 09, 2019 at 05:45:49PM -0500, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.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!
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