There is code in msix_capability_init() which, when the requested number
of MSI-X couldn't be allocated, calculates how many MSI-X /could/ be
allocated and returns that to the driver. That allows the driver to then
make a second request, with a number of MSIs that should succeed.
The current code requires the arch code to setup as many msi_descs as it
can, and then return to the generic code. On some platforms the arch
code may already know how many MSI-X it can allocate, before it sets up
any of the msi_descs.
So change the logic such that if the arch code returns a positive error
code, that is taken to be the number of MSI-X that could be allocated.
If the error code is negative we still calculate the number available
using the old method.
Because it's a little subtle, make sure the error return code from
arch_setup_msi_irq() is always negative. That way only implementations
of arch_setup_msi_irqs() need to be careful about returning a positive
error code.
Signed-off-by: Michael Ellerman <michael@xxxxxxxxxxxxxx>
---
drivers/pci/msi.c | 20 +++++++++++---------
1 files changed, 11 insertions(+), 9 deletions(-)
This is the same patch I sent 20 minutes ago, but sent to the correct
address for linux-pci.
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index aa791db..d065cbc 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -43,7 +43,8 @@ int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
list_for_each_entry(entry, &dev->msi_list, list) {
ret = arch_setup_msi_irq(dev, entry);
if (ret)
- return ret;
+ /* Ensure the error code is always < 0 */
+ return min(ret, -ret);
}
return 0;
@@ -482,7 +483,9 @@ static int msix_capability_init(struct pci_dev *dev,
}
ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
- if (ret) {
+ if (ret < 0) {
+ /* If we had some success report the number of irqs
+ * we succeeded in setting up. */
int avail = 0;
list_for_each_entry(entry, &dev->msi_list, list) {
if (entry->irq != 0) {
@@ -490,14 +493,13 @@ static int msix_capability_init(struct pci_dev *dev,
}
}
- msi_free_irqs(dev);
+ if (avail != 0)
+ ret = avail;
+ }
- /* If we had some success report the number of irqs
- * we succeeded in setting up.
- */
- if (avail == 0)
- avail = ret;
- return avail;
+ if (ret) {
+ msi_free_irqs(dev);
+ return ret;
}
i = 0;
--
1.5.5
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