Re: [PATCH v6 2/3] PCI: Add parameter nr_devfns to pci_add_dma_alias

Bjorn Helgaas
2019-12-10T22:37:59Z

[+cc Joerg]

On Tue, Dec 03, 2019 at 03:43:53PM +0000, James Sewart wrote:
> pci_add_dma_alias can now be used to create a dma alias for a range of
> devfns.
>
> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: James Sewart <jamessewart@arista.com>
> ---
> drivers/pci/pci.c | 22 +++++++++++++++++-----
> drivers/pci/quirks.c | 14 +++++++-------
> include/linux/pci.h | 2 +-
> 3 files changed, 25 insertions(+), 13 deletions(-)

Heads up Joerg: I also updated drivers/iommu/amd_iommu.c (this is the
one reported by the kbuild test robot) and removed the printk there
that prints the same thing as the one in pci_add_dma_alias(), and I
updated a PCI quirk that was merged after this patch was posted.

> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index d3c83248f3ce..dbb01aceafda 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5857,7 +5857,8 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
> /**
> * pci_add_dma_alias - Add a DMA devfn alias for a device
> * @dev: the PCI device for which alias is added
> - * @devfn: alias slot and function
> + * @devfn_from: alias slot and function
> + * @nr_devfns: Number of subsequent devfns to alias
> *
> * This helper encodes an 8-bit devfn as a bit number in dma_alias_mask
> * which is used to program permissible bus-devfn source addresses for DMA
> @@ -5873,8 +5874,13 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
> * cannot be left as a userspace activity). DMA aliases should therefore
> * be configured via quirks, such as the PCI fixup header quirk.
> */
> -void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
> +void pci_add_dma_alias(struct pci_dev *dev, u8 devfn_from, unsigned nr_devfns)
> {
> + int devfn_to;
> +
> + nr_devfns = min(nr_devfns, (unsigned)MAX_NR_DEVFNS);
> + devfn_to = devfn_from + nr_devfns - 1;

I made this look like:

+ devfn_to = min(devfn_from + nr_devfns - 1,
+ (unsigned) MAX_NR_DEVFNS - 1);

so devfn_from=0xf0, nr_devfns=0x20 doesn't cause devfn_to to wrap
around.

I did keep Logan's reviewed-by, so let me know if I broke something.

> if (!dev->dma_alias_mask)
> dev->dma_alias_mask = bitmap_zalloc(MAX_NR_DEVFNS, GFP_KERNEL);
> if (!dev->dma_alias_mask) {
> @@ -5882,9 +5888,15 @@ void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
> return;
> }
>
> - set_bit(devfn, dev->dma_alias_mask);
> - pci_info(dev, "Enabling fixed DMA alias to %02x.%d\n",
> - PCI_SLOT(devfn), PCI_FUNC(devfn));
> + bitmap_set(dev->dma_alias_mask, devfn_from, nr_devfns);
> +
> + if (nr_devfns == 1)
> + pci_info(dev, "Enabling fixed DMA alias to %02x.%d\n",
> + PCI_SLOT(devfn_from), PCI_FUNC(devfn_from));
> + else if(nr_devfns > 1)
> + pci_info(dev, "Enabling fixed DMA alias for devfn range from %02x.%d to %02x.%d\n",
> + PCI_SLOT(devfn_from), PCI_FUNC(devfn_from),
> + PCI_SLOT(devfn_to), PCI_FUNC(devfn_to));
> }