On Tue, Jun 14, 2016 at 09:59:00PM +0200, Christoph Hellwig wrote:
> Add a helper to allocate a range of interrupt vectors, which will
> transparently use MSI-X and MSI if available or fallback to legacy
> vectors. The interrupts are available in a core managed array
> in the pci_dev structure, and can also be released using a similar
> helper.
>
> The next patch will also add automatic spreading of MSI / MSI-X
> vectors to this function.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> drivers/pci/msi.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pci.h | 18 +++++++++
New APIs should be documented in Documentation/PCI/MSI-HOWTO.txt, I guess.
> 2 files changed, 128 insertions(+)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index a080f44..a33adec 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -4,6 +4,7 @@
> *
> * Copyright (C) 2003-2004 Intel
> * Copyright (C) Tom Long Nguyen (tom.l.nguyen@xxxxxxxxx)
> + * Copyright (c) 2016 Christoph Hellwig.
> */
>
> #include <linux/err.h>
> @@ -1120,6 +1121,115 @@ int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
> }
> EXPORT_SYMBOL(pci_enable_msix_range);
>
> +static unsigned int pci_nr_irq_vectors(struct pci_dev *pdev)
> +{
> + int nr_entries;
> +
> + nr_entries = pci_msix_vec_count(pdev);
> + if (nr_entries <= 0 && pci_msi_supported(pdev, 1))
> + nr_entries = pci_msi_vec_count(pdev);
> + if (nr_entries <= 0)
> + nr_entries = 1;
> + return nr_entries;
> +}
This function is strange, because it:
(a) does not consider PCI_IRQ_NOMSIX flag;
(b) only calls pci_msi_supported() for MSI case;
(c) calls pci_msi_supported() with just one vector;
(d) might return suboptimal number of vectors (number of MSI-X used
later for MSI or vice versa)
Overall, I would suggest simply return maximum between MSI-X and MSI
numbers and let the rest of the code (i.e the two range functions)
handle a-d.
> +static int pci_enable_msix_range_wrapper(struct pci_dev *pdev, u32 *irqs,
> + unsigned int min_vecs, unsigned int max_vecs)
> +{
> + struct msix_entry *msix_entries;
> + int vecs, i;
> +
> + msix_entries = kcalloc(max_vecs, sizeof(struct msix_entry), GFP_KERNEL);
> + if (!msix_entries)
> + return -ENOMEM;
> +
> + for (i = 0; i < max_vecs; i++)
> + msix_entries[i].entry = i;
> +
> + vecs = pci_enable_msix_range(pdev, msix_entries, min_vecs, max_vecs);
> + if (vecs > 0) {
This condition check is unneeded.
> + for (i = 0; i < vecs; i++)
> + irqs[i] = msix_entries[i].vector;
> + }
> +
> + kfree(msix_entries);
> + return vecs;
> +}
> +
> +/**
> + * pci_alloc_irq_vectors - allocate multiple IRQs for a device
> + * @dev: PCI device to operate on
> + * @min_vecs: minimum number of vectors required (must be >= 1)
> + * @max_vecs: maximum (desired) number of vectors
> + * @flags: flags or quirks for the allocation
> + *
> + * Allocate up to @max_vecs interrupt vectors for @dev, using MSI-X or MSI
> + * vectors if available, and fall back to a single legacy vector
> + * if neither is available. Return the number of vectors allocated,
> + * (which might be smaller than @max_vecs) if successful, or a negative
> + * error code on error. The Linux irq numbers for the allocated
> + * vectors are stored in pdev->irqs. If less than @min_vecs interrupt
> + * vectors are available for @dev the function will fail with -ENOSPC.
> + */
> +int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
> + unsigned int max_vecs, unsigned int flags)
> +{
> + unsigned int vecs, i;
> + u32 *irqs;
> +
> + max_vecs = min(max_vecs, pci_nr_irq_vectors(dev));
Optionally, you could move this assignment to pci_nr_irq_vectors() and
simply let it handle number of vectors to request.
> + irqs = kcalloc(max_vecs, sizeof(u32), GFP_KERNEL);
> + if (!irqs)
> + return -ENOMEM;
> +
> + if (!(flags & PCI_IRQ_NOMSIX)) {
> + vecs = pci_enable_msix_range_wrapper(dev, irqs, min_vecs,
> + max_vecs);
> + if (vecs > 0)
> + goto done;
> + }
> +
> + vecs = pci_enable_msi_range(dev, min_vecs, max_vecs);
> + if (vecs > 0) {
> + for (i = 0; i < vecs; i++)
> + irqs[i] = dev->irq + i;
> + goto done;
> + }
> +
> + if (min_vecs > 1)
> + return -ENOSPC;
irqs is leaked if (min_vecs > 1)
You can get rid of this check at all if you reorganize your code i.e.
like this:
...
vecs = pci_enable_msi_range(dev, min_vecs, max_vecs);
if (vecs < 0)
goto legacy;
for (i = 0; i < vecs; i++)
irqs[i] = dev->irq + i;
done:
...
legacy:
...
> +
> + /* use legacy irq */
> + kfree(irqs);
> + dev->irqs = &dev->irq;
> + return 1;
> +
> +done:
> + dev->irqs = irqs;
> + return vecs;
> +}
> +EXPORT_SYMBOL(pci_alloc_irq_vectors);
> +
> +/**
> + * pci_free_irq_vectors - free previously allocated IRQs for a device
> + * @dev: PCI device to operate on
> + *
> + * Undoes the allocations and enabling in pci_alloc_irq_vectors().
> + */
> +void pci_free_irq_vectors(struct pci_dev *dev)
> +{
> + if (dev->msix_enabled)
> + pci_disable_msix(dev);
> + else if (dev->msi_enabled)
> + pci_disable_msi(dev);
The checks are probably redundant or incomplete. Redundant - because
pci_disable_msi()/pci_disable_msix() do it anyways:
if (!pci_msi_enable || !dev || !dev->msi_enabled)
return;
Incomplete - because the two other conditions are not checked.
> + if (dev->irqs != &dev->irq)
> + kfree(dev->irqs);
Unset dev->irqs?
BTW, since (dev->irqs == &dev->irq) effectively checks if MSI/MSI-X
was enabled this function could bail out in case they did not.
> +}
> +EXPORT_SYMBOL(pci_free_irq_vectors);
> +
> +
> struct pci_dev *msi_desc_to_pci_dev(struct msi_desc *desc)
> {
> return to_pci_dev(desc->dev);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index b67e4df..84a20fc 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -320,6 +320,7 @@ struct pci_dev {
> * directly, use the values stored here. They might be different!
> */
> unsigned int irq;
> + unsigned int *irqs;
> struct resource resource[DEVICE_COUNT_RESOURCE]; /* I/O and memory regions + expansion ROMs */
>
> bool match_driver; /* Skip attaching driver */
> @@ -1237,6 +1238,8 @@ 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);
>
> +#define PCI_IRQ_NOMSIX (1 << 0) /* don't try to use MSI-X interrupts */
BTW, why PCI_IRQ_NOMSIX only and no PCI_IRQ_NOMSI?
> /* kmem_cache style wrapper around pci_alloc_consistent() */
>
> #include <linux/pci-dma.h>
> @@ -1284,6 +1287,9 @@ static inline int pci_enable_msix_exact(struct pci_dev *dev,
> return rc;
> return 0;
> }
> +int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
> + unsigned int max_vecs, unsigned int flags);
> +void pci_free_irq_vectors(struct pci_dev *dev);
> #else
> static inline int pci_msi_vec_count(struct pci_dev *dev) { return -ENOSYS; }
> static inline void pci_msi_shutdown(struct pci_dev *dev) { }
> @@ -1307,6 +1313,18 @@ static inline int pci_enable_msix_range(struct pci_dev *dev,
> static inline int pci_enable_msix_exact(struct pci_dev *dev,
> struct msix_entry *entries, int nvec)
> { return -ENOSYS; }
> +static inline int pci_alloc_irq_vectors(struct pci_dev *dev,
> + unsigned int min_vecs, unsigned int max_vecs,
> + unsigned int flags)
> +{
> + if (min_vecs > 1)
> + return -ENOSPC;
> + dev->irqs = &dev->irq;
> + return 1;
> +}
> +static inline void pci_free_irq_vectors(struct pci_dev *dev)
> +{
Unset dev->irqs?
> +}
> #endif
>
> #ifdef CONFIG_PCIEPORTBUS
> --
> 2.1.4
>
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