Hi Michael, On Thu, Mar 19, 2015 at 07:57:52PM +0100, Michael S. Tsirkin wrote: > commit d52877c7b1afb8c37ebe17e2005040b79cb618b0 > pci/irq: let pci_device_shutdown to call pci_msi_shutdown v2 > > attempted to address the problem of kexec getting > started after linux enabled msi/msix for a device, > and drivers being confused by msi being enabled, > by disabling msi at shutdown. > > But arguably, it's better to disable msi/msix when kexec > starts - for example, kexec might run after a crash (kdump) > and shutdown callbacks are not always invoked in that case. > > Cc: Yinghai Lu <yhlu.kernel.send@xxxxxxxxx> > Cc: Ulrich Obergfell <uobergfe@xxxxxxxxxx> > Cc: Fam Zheng <famz@xxxxxxxxxx> > Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > --- > drivers/pci/pci-driver.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 3cb2210..2ebd2a8 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -305,6 +305,12 @@ static long local_pci_probe(void *_ddi) > */ > pm_runtime_get_sync(dev); > pci_dev->driver = pci_drv; > + /* > + * When using kexec, msi might be left enabled by the previous kernel, > + * this breaks things as some drivers assume msi/msi-x is off at boot. > + * Fix this by forcing msi off at startup. > + */ > + pci_msi_off(pci_dev); I think this makes sense, but I have a few questions. This is a device initialization thing, so it seems like a better fit for the enumeration path, e.g,. pci_msi_init_pci_dev(), than for the driver binding path. But when CONFIG_PCI_MSI=y, pci_msi_init_pci_dev() already does basically the same thing, so we shouldn't need this change unless CONFIG_PCI_MSI is not set in the kdump kernel. If this is a problem just with kexeced kernels that don't have CONFIG_PCI_MSI=y, I think I would prefer to fix this by moving pci_msi_init_pci_dev() outside the #ifdef so it works regardless of CONFIG_PCI_MSI. That would also be nice because we could clean up the duplication between pci_msi_off() and pci_msi_init_pci_dev(). It would also make the starting machine state less dependent on the new kernel, which seems like a good thing. Are there any bugzillas we could reference here? > rc = pci_drv->probe(pci_dev, ddi->id); > if (!rc) > return rc; > -- > MST > -- 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
