linux-kernel - Re: [PATCH 1/2] iommu/vt-d: Select PCI_PRI for INTEL_IOMMU

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Date:   Wed, 9 Oct 2019 16:42:10 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        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,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 1/2] iommu/vt-d: Select PCI_PRI for INTEL_IOMMU_SVM


On 10/9/19 3:45 PM, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
>
> 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.
>
> Previously INTEL_IOMMU_SVM selected PCI_PASID but not PCI_PRI, so the state
> of PCI_PRI depended on whether AMD_IOMMU (which selects PCI_PRI) was
> enabled or PCI_PRI was enabled explicitly.
>
> The behavior of iommu_enable_dev_iotlb() should not depend on whether
> AMD_IOMMU is enabled.  Make it predictable by having INTEL_IOMMU_SVM select
> PCI_PRI so iommu_enable_dev_iotlb() always uses the full implementations of
> PRI interfaces.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>

Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan 
<sathyanarayanan.kuppuswamy@...ux.intel.com>

> ---
>   drivers/iommu/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index e3842eabcfdd..b183c9f916b0 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -207,6 +207,7 @@ config INTEL_IOMMU_SVM
>   	bool "Support for Shared Virtual Memory with Intel IOMMU"
>   	depends on INTEL_IOMMU && X86
>   	select PCI_PASID
> +	select PCI_PRI
>   	select MMU_NOTIFIER
>   	help
>   	  Shared Virtual Memory (SVM) provides a facility for devices

-- 
Sathyanarayanan Kuppuswamy
Linux kernel developer