2020-06-09 10:48:00

by Piotr Stankiewicz

Subject: [PATCH v3 01/15] PCI/MSI: Forward MSI-X vector enable error code in pci_alloc_irq_vectors_affinity()

When debugging an issue where I was asking the PCI machinery to enable a
set of MSI-X vectors, without falling back on MSI, I ran across a
behaviour which seems odd. The pci_alloc_irq_vectors_affinity() will
always return -ENOSPC on failure, when allocating MSI-X vectors only,
whereas with MSI fallback it will forward any error returned by
__pci_enable_msi_range(). This is a confusing behaviour, so have the
pci_alloc_irq_vectors_affinity() forward the error code from
__pci_enable_msix_range() when appropriate.

Signed-off-by: Piotr Stankiewicz <[email protected]>
---
drivers/pci/msi.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 6b43a5455c7a..cade9be68b09 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1191,8 +1191,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
struct irq_affinity *affd)
{
struct irq_affinity msi_default_affd = {0};
- int msix_vecs = -ENOSPC;
- int msi_vecs = -ENOSPC;
+ int nvecs = -ENOSPC;

if (flags & PCI_IRQ_AFFINITY) {
if (!affd)
@@ -1203,17 +1202,16 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
}

if (flags & PCI_IRQ_MSIX) {
- msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,
- max_vecs, affd, flags);
- if (msix_vecs > 0)
- return msix_vecs;
+ nvecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
+ affd, flags);
+ if (nvecs > 0)
+ return nvecs;
}

if (flags & PCI_IRQ_MSI) {
- msi_vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs,
- affd);
- if (msi_vecs > 0)
- return msi_vecs;
+ nvecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, affd);
+ if (nvecs > 0)
+ return nvecs;
}

/* use legacy IRQ if allowed */
@@ -1231,9 +1229,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
}
}

- if (msix_vecs == -ENOSPC)
- return -ENOSPC;
- return msi_vecs;
+ return nvecs;
}
EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);

--
2.17.2

2020-06-09 15:53:14

by Christoph Hellwig

Subject: Re: [PATCH v3 01/15] PCI/MSI: Forward MSI-X vector enable error code in pci_alloc_irq_vectors_affinity()

Looks good,

Reviewed-by: Christoph Hellwig <[email protected]>

2020-06-09 17:50:11

by Logan Gunthorpe

Subject: Re: [PATCH v3 01/15] PCI/MSI: Forward MSI-X vector enable error code in pci_alloc_irq_vectors_affinity()

On 2020-06-09 3:14 a.m., Piotr Stankiewicz wrote:
> When debugging an issue where I was asking the PCI machinery to enable a
> set of MSI-X vectors, without falling back on MSI, I ran across a
> behaviour which seems odd. The pci_alloc_irq_vectors_affinity() will
> always return -ENOSPC on failure, when allocating MSI-X vectors only,
> whereas with MSI fallback it will forward any error returned by
> __pci_enable_msi_range(). This is a confusing behaviour, so have the
> pci_alloc_irq_vectors_affinity() forward the error code from
> __pci_enable_msix_range() when appropriate.
>
> Signed-off-by: Piotr Stankiewicz <[email protected]>

Looks fine to me:

Reviewed-by: Logan Gunthorpe <[email protected]>

Thanks!

> ---
> drivers/pci/msi.c | 22 +++++++++-------------
> 1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 6b43a5455c7a..cade9be68b09 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1191,8 +1191,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
> struct irq_affinity *affd)
> {
> struct irq_affinity msi_default_affd = {0};
> - int msix_vecs = -ENOSPC;
> - int msi_vecs = -ENOSPC;
> + int nvecs = -ENOSPC;
>
> if (flags & PCI_IRQ_AFFINITY) {
> if (!affd)
> @@ -1203,17 +1202,16 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
> }
>
> if (flags & PCI_IRQ_MSIX) {
> - msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,
> - max_vecs, affd, flags);
> - if (msix_vecs > 0)
> - return msix_vecs;
> + nvecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
> + affd, flags);
> + if (nvecs > 0)
> + return nvecs;
> }
>
> if (flags & PCI_IRQ_MSI) {
> - msi_vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs,
> - affd);
> - if (msi_vecs > 0)
> - return msi_vecs;
> + nvecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, affd);
> + if (nvecs > 0)
> + return nvecs;
> }
>
> /* use legacy IRQ if allowed */
> @@ -1231,9 +1229,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
> }
> }
>
> - if (msix_vecs == -ENOSPC)
> - return -ENOSPC;
> - return msi_vecs;
> + return nvecs;
> }
> EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);
>
>