Re: [PATCH] pci: Add support for multiple DMA aliases

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On Mon, Jan 18, 2016 at 05:07:47PM +0100, Jacek Lawrynowicz wrote:
> This patch solves IOMMU support issues with PCIe non-transparent bridges
> that use Requester ID look-up tables (LUT), e.g. PEX8733. Before exiting
> the bridge, packet's RID is rewritten according to LUT programmed by
> a driver. Modified packets are then passed to a destination bus and
> processed upstream. The problem is that such packets seem to come from
> non-existent nodes that are hidden behind NTB and are not discoverable
> by a destination node, so IOMMU discards them. Adding DMA alias for a
> given LUT entry allows IOMMU to create a proper mapping that enables
> inter-node communication.
> 
> The current DMA alias implementation supports only single alias, so it's
> not possible to connect more than two nodes when IOMMU is enabled. This
> implementation enables all possible aliases on a given bus (256) that
> are stored in a bitset. Alias devfn is directly translated to a bit
> number. The bitset is not allocated for devices that have no need for
> DMA aliases.
> 
> More details can be found in following article:
> http://www.plxtech.com/files/pdf/technical/expresslane/RTC_Enabling%20MulitHostSystemDesigns.pdf
> 
> Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@xxxxxxxxx>
> Acked-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
> Acked-by: Joerg Roedel <jroedel@xxxxxxx>

I applied this to pci/iommu and intend to merge it for v4.5.

I made the following change because the kcalloc() failure warning in
your patch looks wrong:

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b0d6a0a..29cfe1a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4577,13 +4577,15 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
  */
 void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
 {
-	if (!dev->dma_alias_mask) {
+	if (!dev->dma_alias_mask)
 		dev->dma_alias_mask = kcalloc(BITS_TO_LONGS(U8_MAX),
 					      sizeof(long), GFP_KERNEL);
-		dev_warn(&dev->dev, "Unable to allocate DMA alias mask.\n");
+	if (!dev->dma_alias_mask) {
+		dev_warn(&dev->dev, "Unable to allocate DMA alias mask\n");
+		return;
 	}
-	if (dev->dma_alias_mask)
-		set_bit(devfn, dev->dma_alias_mask);
+
+	set_bit(devfn, dev->dma_alias_mask);
 }
 EXPORT_SYMBOL_GPL(pci_add_dma_alias);
 

> ---
>  drivers/iommu/iommu.c |  8 ++++----
>  drivers/pci/pci.c     | 19 +++++++++++++++++++
>  drivers/pci/probe.c   |  1 +
>  drivers/pci/quirks.c  | 15 ++++++---------
>  drivers/pci/search.c  | 14 +++++++++-----
>  include/linux/pci.h   | 15 ++++++++-------
>  6 files changed, 47 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index abae363..98ae7ff 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -686,10 +686,10 @@ static struct iommu_group *get_pci_alias_group(struct pci_dev *pdev,
>  			continue;
>  
>  		/* We alias them or they alias us */
> -		if (((pdev->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN) &&
> -		     pdev->dma_alias_devfn == tmp->devfn) ||
> -		    ((tmp->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN) &&
> -		     tmp->dma_alias_devfn == pdev->devfn)) {
> +		if ((pdev->dma_alias_mask &&
> +		     test_bit(tmp->devfn, pdev->dma_alias_mask)) ||
> +		    ((tmp->dma_alias_mask &&
> +		     test_bit(pdev->devfn, tmp->dma_alias_mask)))) {
>  
>  			group = get_pci_alias_group(tmp, devfns);
>  			if (group) {
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 49e3715..5b27d65 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4568,6 +4568,25 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
>  	return 0;
>  }
>  
> +/**
> + * pci_add_dma_alias - Allows to add multiple devfn aliases for given device
> + * @dev: the PCI device for which alias is added
> + * @devfn: alias slot and function
> + *
> + * This helper encodes 8-bit devfn as bit number in dma_alias_mask
> + */
> +void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
> +{
> +	if (!dev->dma_alias_mask) {
> +		dev->dma_alias_mask = kcalloc(BITS_TO_LONGS(U8_MAX),
> +					      sizeof(long), GFP_KERNEL);
> +		dev_warn(&dev->dev, "Unable to allocate DMA alias mask.\n");
> +	}
> +	if (dev->dma_alias_mask)
> +		set_bit(devfn, dev->dma_alias_mask);
> +}
> +EXPORT_SYMBOL_GPL(pci_add_dma_alias);
> +
>  bool pci_device_is_present(struct pci_dev *pdev)
>  {
>  	u32 v;
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 32b9f1b..5da4dd3 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1501,6 +1501,7 @@ static void pci_release_dev(struct device *dev)
>  	pcibios_release_device(pci_dev);
>  	pci_bus_put(pci_dev->bus);
>  	kfree(pci_dev->driver_override);
> +	kfree(pci_dev->dma_alias_mask);
>  	kfree(pci_dev);
>  }
>  
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 83e93d7..3ed1f9a 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3579,8 +3579,7 @@ int pci_dev_specific_reset(struct pci_dev *dev, int probe)
>  static void quirk_dma_func0_alias(struct pci_dev *dev)
>  {
>  	if (PCI_FUNC(dev->devfn) != 0) {
> -		dev->dma_alias_devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 0);
> -		dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN;
> +		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
>  	}
>  }
>  
> @@ -3595,8 +3594,7 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_RICOH, 0xe476, quirk_dma_func0_alias);
>  static void quirk_dma_func1_alias(struct pci_dev *dev)
>  {
>  	if (PCI_FUNC(dev->devfn) != 1) {
> -		dev->dma_alias_devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 1);
> -		dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN;
> +		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 1));
>  	}
>  }
>  
> @@ -3660,11 +3658,10 @@ static void quirk_fixed_dma_alias(struct pci_dev *dev)
>  
>  	id = pci_match_id(fixed_dma_alias_tbl, dev);
>  	if (id) {
> -		dev->dma_alias_devfn = id->driver_data;
> -		dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN;
> -		dev_info(&dev->dev, "Enabling fixed DMA alias to %02x.%d\n",
> -			 PCI_SLOT(dev->dma_alias_devfn),
> -			 PCI_FUNC(dev->dma_alias_devfn));
> +		pci_add_dma_alias(dev, id->driver_data);
> +		dev_info(&dev->dev, "Enabling fixed DMA alias to %02lx.%ld\n",
> +			 PCI_SLOT(id->driver_data),
> +			 PCI_FUNC(id->driver_data));
>  	}
>  }
>  
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> index a20ce7d..33e0f03 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -40,11 +40,15 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
>  	 * If the device is broken and uses an alias requester ID for
>  	 * DMA, iterate over that too.
>  	 */
> -	if (unlikely(pdev->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN)) {
> -		ret = fn(pdev, PCI_DEVID(pdev->bus->number,
> -					 pdev->dma_alias_devfn), data);
> -		if (ret)
> -			return ret;
> +	if (unlikely(pdev->dma_alias_mask)) {
> +		u8 devfn;
> +
> +		for_each_set_bit(devfn, pdev->dma_alias_mask, U8_MAX) {
> +			ret = fn(pdev, PCI_DEVID(pdev->bus->number, devfn),
> +				 data);
> +			if (ret)
> +				return ret;
> +		}
>  	}
>  
>  	for (bus = pdev->bus; !pci_is_root_bus(bus); bus = bus->parent) {
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index f9f79ad..6200175 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -172,16 +172,14 @@ enum pci_dev_flags {
>  	PCI_DEV_FLAGS_ASSIGNED = (__force pci_dev_flags_t) (1 << 2),
>  	/* Flag for quirk use to store if quirk-specific ACS is enabled */
>  	PCI_DEV_FLAGS_ACS_ENABLED_QUIRK = (__force pci_dev_flags_t) (1 << 3),
> -	/* Flag to indicate the device uses dma_alias_devfn */
> -	PCI_DEV_FLAGS_DMA_ALIAS_DEVFN = (__force pci_dev_flags_t) (1 << 4),
>  	/* Use a PCIe-to-PCI bridge alias even if !pci_is_pcie */
> -	PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS = (__force pci_dev_flags_t) (1 << 5),
> +	PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS = (__force pci_dev_flags_t) (1 << 4),
>  	/* Do not use bus resets for device */
> -	PCI_DEV_FLAGS_NO_BUS_RESET = (__force pci_dev_flags_t) (1 << 6),
> +	PCI_DEV_FLAGS_NO_BUS_RESET = (__force pci_dev_flags_t) (1 << 5),
>  	/* Do not use PM reset even if device advertises NoSoftRst- */
> -	PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 7),
> +	PCI_DEV_FLAGS_NO_PM_RESET = (__force pci_dev_flags_t) (1 << 6),
>  	/* Get VPD from function 0 VPD */
> -	PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8),
> +	PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 7),
>  };
>  
>  enum pci_irq_reroute_variant {
> @@ -279,7 +277,7 @@ struct pci_dev {
>  	u8		rom_base_reg;	/* which config register controls the ROM */
>  	u8		pin;		/* which interrupt pin this device uses */
>  	u16		pcie_flags_reg;	/* cached PCIe Capabilities Register */
> -	u8		dma_alias_devfn;/* devfn of DMA alias, if any */
> +	unsigned long	*dma_alias_mask;/* mask of enabled devfn aliases */
>  
>  	struct pci_driver *driver;	/* which driver has allocated this device */
>  	u64		dma_mask;	/* Mask of the bits of bus address this
> @@ -1229,6 +1227,9 @@ resource_size_t pcibios_iov_resource_alignment(struct pci_dev *dev, int resno);
>  
>  int pci_set_vga_state(struct pci_dev *pdev, bool decode,
>  		      unsigned int command_bits, u32 flags);
> +
> +void pci_add_dma_alias(struct pci_dev *dev, u8 devfn);
> +
>  /* kmem_cache style wrapper around pci_alloc_consistent() */
>  
>  #include <linux/pci-dma.h>
> -- 
> 2.1.4
> 
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