[PATCH] PCI:MSI Return -ENOSPC when requested vectors is not enough
From: helgaas@kernel.org (Bjorn Helgaas)
Date: 2017-01-11 18:18:53
Also in:
linux-ide, linux-pci
On Thu, Dec 01, 2016 at 10:15:04AM +0800, Dennis Chen wrote:
The __pci_enable_msi_range() should return -ENOSPC instead of -EINVAL
when the device doesn't have enough vectors as required, just as the
MSI-X vector allocator does in __pci_enable_msix_range(). Otherwise,
some drivers depending on that return value will probably fallback to
the legacy interrupt directly, for example, in commit 17a51f12cfbd2814
("ahci: only try to use multi-MSI mode if there is more than 1 port"), the
ahci driver will fallback to single MSI mode only when the return value
is -ENOSPC in case of required vectors is not enough, else the driver will
use legacy interrupt which has been observed on a x86 box with 6-port SATA
controller.Unless Christoph objects, I'll apply this, but I don't understand the situation with 17a51f12cfbd. That commit doesn't check for EINVAL or ENOSPC so I don't know what the connection with this patch is. I know Christoph said he changed something in ahci to treat all errors the same, but I don't know where that is, either. If there's a revision of Linus' tree that is broken, please give the details so I can at least describe which versions are broken, when it got fixed by Christoph, and figure out whether we need stable backports or anything. Bjorn
quoted hunk ↗ jump to hunk
With this patch, when a MSI-capable device doesn't have enough MSI vectors as requested, it will fallback to single MSI mode while not legacy interrupt. Signed-off-by: Dennis Chen <redacted> Cc: Tejun Heo <tj@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Tom Long Nguyen <redacted> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Marc Zyngier <redacted> Cc: Lorenzo Pieralisi <redacted> Cc: Steve Capper <redacted> Cc: linux-ide at vger.kernel.org Cc: linux-arm-kernel at lists.infradead.org --- drivers/pci/msi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index ad70507..da37113 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c@@ -1084,7 +1084,7 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec, if (nvec < 0) return nvec; if (nvec < minvec) - return -EINVAL; + return -ENOSPC; if (nvec > maxvec) nvec = maxvec;-- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel at lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel