linux-kernel - Re: [PATCH v2 6/7] intel-iommu: Make use of DMA quirks and ACS checks in IOMMU groups

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Date:	Thu, 31 May 2012 15:47:49 -0400
From:	Don Dutile <ddutile@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
CC:	joerg.roedel@....com, dwmw2@...radead.org,
	iommu@...ts.linux-foundation.org, bhelgaas@...gle.com,
	benh@...nel.crashing.org, aik@...abs.ru,
	david@...son.dropbear.id.au, konrad.wilk@...cle.com,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	gregkh@...uxfoundation.org, liuj97@...il.com
Subject: Re: [PATCH v2 6/7] intel-iommu: Make use of DMA quirks and ACS checks
 in IOMMU groups

On 05/30/2012 04:19 PM, Alex Williamson wrote:
> Work around broken devices and adhere to ACS support when determining
> IOMMU grouping.
>
> Signed-off-by: Alex Williamson<alex.williamson@...hat.com>
> ---
>
>   drivers/iommu/intel-iommu.c |   25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 4a43452..ebf2b31 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -4090,6 +4090,14 @@ static int intel_iommu_domain_has_cap(struct iommu_domain *domain,
>   	return 0;
>   }
>
> +static void swap_pci_ref(struct pci_dev **from, struct pci_dev *to)
> +{
> +	pci_dev_put(*from);
> +	*from = to;
> +}
> +
> +#define REQ_ACS_FLAGS	(PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF)
> +
>   static int intel_iommu_add_device(struct device *dev)
>   {
>   	struct pci_dev *pdev = to_pci_dev(dev);
> @@ -4112,6 +4120,23 @@ static int intel_iommu_add_device(struct device *dev)
>   	} else
>   		dma_pdev = pci_dev_get(pdev);
>
> +	swap_pci_ref(&dma_pdev, pci_get_dma_source(dma_pdev));
> +
> +	if (dma_pdev->multifunction&&
> +	    !pci_acs_enabled(dma_pdev, REQ_ACS_FLAGS))
> +		swap_pci_ref(&dma_pdev,
> +			     pci_get_slot(dma_pdev->bus,
> +					  PCI_DEVFN(PCI_SLOT(dma_pdev->devfn),
> +					  0)));
> +
> +	while (!pci_is_root_bus(dma_pdev->bus)) {
> +		if (pci_acs_path_enabled(dma_pdev->bus->self,
> +					 NULL, REQ_ACS_FLAGS))
> +			break;
> +
> +		swap_pci_ref(&dma_pdev, pci_dev_get(dma_pdev->bus->self));
> +	}
> +
I'm having deja-vu on this patch....
.... why not just make the above two patches as two functions in drivers/iommu/iommu.c,
one exported for these two modules (and maybe others someday...), e.g., iommu_pdev_put())
which [intel-,amd-]iommu.c call ?

  
>   	group = iommu_group_get(&dma_pdev->dev);
>   	pci_dev_put(dma_pdev);
>   	if (!group) {
>

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