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SubjectRe: [PATCH] msi-x: let drivers retry when not enough vectors
Date
On Thursday 07 May 2009 16:28:41 Michael S. Tsirkin wrote:
> pci_enable_msix currently returns -EINVAL if you ask
> for more vectors than supported by the device, which would
> typically cause fallback to regular interrupts.
>
> It's better to return the table size, making the driver retry
> MSI-X with less vectors.

Hi Michael

I think driver should read from capability list to know how many vector
supported by this device before enable MSI-X for device, as
pci_msix_table_size() did...

--
regards
Yang, Sheng

>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
> Hi Jesse,
> This came up when I was adding MSI-X support to virtio pci driver,
> which does not know the exact table size upfront.
> Could you consider this patch for 2.6.31 please?
>
>
> drivers/pci/msi.c | 6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 6f2e629..f5bd1c9 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -687,8 +687,8 @@ int pci_msix_table_size(struct pci_dev *dev)
> * indicates the successful configuration of MSI-X capability structure
> * with new allocated MSI-X irqs. A return of < 0 indicates a failure.
> * Or a return of > 0 indicates that driver request is exceeding the
> number - * of irqs available. Driver should use the returned value to
> re-send - * its request.
> + * of irqs or MSI-X vectors available. Driver should use the returned
> value to + * re-send its request.
> **/
> int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int
> nvec) {
> @@ -704,7 +704,7 @@ int pci_enable_msix(struct pci_dev* dev, struct
> msix_entry *entries, int nvec)
>
> nr_entries = pci_msix_table_size(dev);
> if (nvec > nr_entries)
> - return -EINVAL;
> + return nr_entries;
>
> /* Check for any invalid entries */
> for (i = 0; i < nvec; i++) {




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