On Mon, Mar 23, 2015 at 01:50:06PM -0500, Bjorn Helgaas wrote:
> 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.
What you say above makes sense.
OK so the simplest fix is something like below then.
Fixes the duplication and kexec for CONFIG_PCI_MSI=n.
Acceptable? Pls let me know, if yes I'll test and
resubmit properly.
> Are there any bugzillas we could reference here?
I'll check this point. Maybe not - the real bugfix is
patch 2/4, this was just found by reading code,
but it's a dependency to make sure 2/4 does not
introduce regressions.
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 0e037af..2ab59d4 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1062,18 +1062,8 @@ EXPORT_SYMBOL(pci_msi_enabled);
void pci_msi_init_pci_dev(struct pci_dev *dev)
{
INIT_LIST_HEAD(&dev->msi_list);
-
- /* Disable the msi hardware to avoid screaming interrupts
- * during boot. This is the power on reset default so
- * usually this should be a noop.
- */
dev->msi_cap = pci_find_capability(dev, PCI_CAP_ID_MSI);
- if (dev->msi_cap)
- msi_set_enable(dev, 0);
-
dev->msix_cap = pci_find_capability(dev, PCI_CAP_ID_MSIX);
- if (dev->msix_cap)
- msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
}
/**
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8d2f400..c455501 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1485,6 +1485,12 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)
static void pci_init_capabilities(struct pci_dev *dev)
{
+ /* Disable the msi hardware to avoid screaming interrupts
+ * during boot. This is the power on reset default so
+ * usually this should be a noop.
+ */
+ pci_msi_off(dev);
+
/* MSI/MSI-X list */
pci_msi_init_pci_dev(dev);
--
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