Fam Zheng [off-list ref] writes:

On Thu, 03/12 23:09, Bandan Das wrote:

quoted

Ccing Alex, he can probably confirm if my understanding is indeed correct.

Fam Zheng [off-list ref] writes:

quoted

On Thu, 03/12 19:56, Bandan Das wrote:

quoted

Hi Fam,

Fam Zheng [off-list ref] writes:

quoted

If the device doesn't support shutdown, disabling interrupts may cause
trouble. For example, virtio-scsi-pci doesn't implement shutdown, and
after we disable MSI-X, futher notifications from device will be
delivered to IRQ, which is unexpected. This IRQ will not be cleared, and
may prevent us from making progress, by keep triggering interrupts.

Signed-off-by: Fam Zheng <redacted>
---
 drivers/pci/pci-driver.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 3cb2210..fb29c96 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c

@@ -448,10 +448,11 @@ static void pci_device_shutdown(struct device *dev)
 
 	pm_runtime_resume(dev);
 
-	if (drv && drv->shutdown)
+	if (drv && drv->shutdown) {
 		drv->shutdown(pci_dev);
-	pci_msi_shutdown(pci_dev);
-	pci_msix_shutdown(pci_dev);
+		pci_msi_shutdown(pci_dev);
+		pci_msix_shutdown(pci_dev);
+	}

If the driver doesn't provide a shutdown method and doesn't itself
disable MSI/MSI-X, then pci_msi(x)_shutdown won't be called anymore,
no ?

Right.

quoted

This is probably ok (but unclean) for a system shutdown, but could
cause problems for something like kexec ?

Doesn't the reset in kexec clean this up during initialization?

I guess it would take the same path as a reboot.

I don't understand, do you mean that no reset will be done before more
operations on the device?

I meant that it's upto the individual driver, pci will take the same path
as a regular reboot.

quoted

quoted

Without shutdown, anything in the driver is unclean anyway, for example
free_irq is not called.

True, And that is why the MSI/-X shutdown functions are called here
because pci can't always rely on the individual device drivers to do
the right thing, but atleast can make a best effort at cleaning up.

This virtio-scsi case shows us that intermediate state is bad, so I still think
we should call pci_msix_shutdown conditionally.

Fam