On 2015/5/19 23:26, Michael S. Tsirkin wrote: > On Tue, May 19, 2015 at 05:16:54PM +0200, Michael S. Tsirkin wrote: >> On Tue, May 19, 2015 at 10:08:38AM -0500, Bjorn Helgaas wrote: >>> [+cc Michael] >>> >>> On Thu, May 07, 2015 at 11:12:52AM +0800, Jiang Liu wrote: >>>> Once PCI MSI/MSI-X is enabled by the device driver, PCI device won't >>>> make use of legacy PCI IRQ until PCI MSI/MSI-X is disabled again. >>>> So optionally free legacy PCI IRQ when enabling MSI/MSI-X and reallocate >>>> when disabling MSI/MSI-X. >>>> >>>> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx> >>>> --- >>>> drivers/pci/msi.c | 6 +++++- >>>> 1 file changed, 5 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c >>>> index c3e7dfcf9ff5..47cf72c669f0 100644 >>>> --- a/drivers/pci/msi.c >>>> +++ b/drivers/pci/msi.c >>>> @@ -686,6 +686,7 @@ static int msi_capability_init(struct pci_dev *dev, int nvec) >>>> msi_set_enable(dev, 1); >>>> dev->msi_enabled = 1; >>>> >>>> + pcibios_free_irq(dev); >>> >>> >From the recent discussion about disabling MSI at shutdown, I seem to >>> recall that turning off bus mastering also effectively disables MSI and >>> causes at least some devices to revert to using INTx. > > So to stress this point, turning off bus mastering also effectively > disables MSI without making devices revert to using INTx. > This is why clearing bus master is the right thing to do > if you don't want any interrupts at all. Thanks for explanation, Michael:) -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
