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

Bjorn Helgaas
2019-12-11T20:56:24Z

On Wed, Dec 11, 2019 at 03:37:30PM +0000, James Sewart wrote:
> > On 10 Dec 2019, at 22:37, Bjorn Helgaas <helgaas@kernel.org> wrote:
> >> -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.
>
> I think nr_devfns still needs updating as it is used for bitmap_set.
> Although thinking about it now we should limit the number to alias to be
> maximum (MAX_NR_DEVFNS - devfn_from), so that we don’t set past the end of
> the bitmap:
>
> nr_devfns = min(nr_devfns, (unsigned) MAX_NR_DEVFNS - devfn_from);
>
> I think with this change we wont need to clip devfn_to.

Indeed, you're right, thanks! I put this in, so it now looks like
the following. I dropped Logan's reviewed-by to avoid putting words
in his mouth ;)

commit 5ddcd840395a ("PCI: Add nr_devfns parameter to pci_add_dma_alias()")
Author: James Sewart <jamessewart@arista.com>
Date: Tue Dec 10 16:07:30 2019 -0600

PCI: Add nr_devfns parameter to pci_add_dma_alias()

Add a "nr_devfns" parameter to pci_add_dma_alias() so it can be used to
create DMA aliases for a range of devfns.

[bhelgaas: incorporate nr_devfns fix from James, update
quirk_pex_vca_alias() and setup_aliases()]
Signed-off-by: James Sewart <jamessewart@arista.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index bd25674ee4db..7a6c056b9b9c 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -230,11 +230,8 @@ static struct pci_dev *setup_aliases(struct device *dev)
*/
ivrs_alias = amd_iommu_alias_table[pci_dev_id(pdev)];
if (ivrs_alias != pci_dev_id(pdev) &&
- PCI_BUS_NUM(ivrs_alias) == pdev->bus->number) {
- pci_add_dma_alias(pdev, ivrs_alias & 0xff);
- pci_info(pdev, "Added PCI DMA alias %02x.%d\n",
- PCI_SLOT(ivrs_alias), PCI_FUNC(ivrs_alias));
- }
+ PCI_BUS_NUM(ivrs_alias) == pdev->bus->number)
+ pci_add_dma_alias(pdev, ivrs_alias & 0xff, 1);

clone_aliases(pdev);

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7b5fa2eabe09..951099279192 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5998,7 +5998,8 @@ EXPORT_SYMBOL_GPL(pci_pr3_present);
/**
* 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
@@ -6014,8 +6015,13 @@ EXPORT_SYMBOL_GPL(pci_pr3_present);
* 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_from);
+ devfn_to = devfn_from + nr_devfns - 1;
+
if (!dev->dma_alias_mask)
dev->dma_alias_mask = bitmap_zalloc(MAX_NR_DEVFNS, GFP_KERNEL);
if (!dev->dma_alias_mask) {
@@ -6023,9 +6029,15 @@ 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));
}

bool pci_devs_are_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2)
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 4937a088d7d8..2fcad18622eb 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3932,7 +3932,7 @@ 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)
- pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
+ pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 0), 1);
}

/*
@@ -3946,7 +3946,7 @@ 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)
- pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 1));
+ pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 1), 1);
}

/*
@@ -4031,7 +4031,7 @@ static void quirk_fixed_dma_alias(struct pci_dev *dev)

id = pci_match_id(fixed_dma_alias_tbl, dev);
if (id)
- pci_add_dma_alias(dev, id->driver_data);
+ pci_add_dma_alias(dev, id->driver_data, 1);
}
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ADAPTEC2, 0x0285, quirk_fixed_dma_alias);

@@ -4072,9 +4072,9 @@ DECLARE_PCI_FIXUP_HEADER(0x8086, 0x244e, quirk_use_pcie_bridge_dma_alias);
*/
static void quirk_mic_x200_dma_alias(struct pci_dev *pdev)
{
- pci_add_dma_alias(pdev, PCI_DEVFN(0x10, 0x0));
- pci_add_dma_alias(pdev, PCI_DEVFN(0x11, 0x0));
- pci_add_dma_alias(pdev, PCI_DEVFN(0x12, 0x3));
+ pci_add_dma_alias(pdev, PCI_DEVFN(0x10, 0x0), 1);
+ pci_add_dma_alias(pdev, PCI_DEVFN(0x11, 0x0), 1);
+ pci_add_dma_alias(pdev, PCI_DEVFN(0x12, 0x3), 1);
}
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2260, quirk_mic_x200_dma_alias);
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2264, quirk_mic_x200_dma_alias);
@@ -4098,13 +4098,8 @@ static void quirk_pex_vca_alias(struct pci_dev *pdev)
const unsigned int num_pci_slots = 0x20;
unsigned int slot;

- for (slot = 0; slot < num_pci_slots; slot++) {
- pci_add_dma_alias(pdev, PCI_DEVFN(slot, 0x0));
- pci_add_dma_alias(pdev, PCI_DEVFN(slot, 0x1));
- pci_add_dma_alias(pdev, PCI_DEVFN(slot, 0x2));
- pci_add_dma_alias(pdev, PCI_DEVFN(slot, 0x3));
- pci_add_dma_alias(pdev, PCI_DEVFN(slot, 0x4));
- }
+ for (slot = 0; slot < num_pci_slots; slot++)
+ pci_add_dma_alias(pdev, PCI_DEVFN(slot, 0x0), 5);
}
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2954, quirk_pex_vca_alias);
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2955, quirk_pex_vca_alias);
@@ -5332,7 +5327,7 @@ static void quirk_switchtec_ntb_dma_alias(struct pci_dev *pdev)
pci_dbg(pdev,
"Aliasing Partition %d Proxy ID %02x.%d\n",
pp, PCI_SLOT(devfn), PCI_FUNC(devfn));
- pci_add_dma_alias(pdev, devfn);
+ pci_add_dma_alias(pdev, devfn, 1);
}
}

diff --git a/include/linux/pci.h b/include/linux/pci.h
index c393dff2d66f..930fab293073 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2310,7 +2310,7 @@ static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
}
#endif

-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);
bool pci_devs_are_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2);
int pci_for_each_dma_alias(struct pci_dev *pdev,
int (*fn)(struct pci_dev *pdev,