[PATCH RFC 0/4] pci: fix unhandled interrupt on shutdown

[PATCH RFC 0/4] pci: fix unhandled interrupt on shutdown

[Michael S. Tsirkin]

Fam Zheng noticed that pci shutdown disables msi and msix of a device while
device is still active. This was intended to fix kexec with fusion devices but
had the unintended effect of breaking even regular shutdown when using virtio.

The same problem would affect any driver which doesn't register
a level interrupt handler when using msix.

I think the fix is to avoid touching device on shutdown:
we clear bus master anyway, so we won't get any more
msi interrupts, and bus reset will clear the msi/msix
state eventually anyway.

Fam, could you please confirm whether this patchset fixes
the problem you have observed?

Thanks!

Michael S. Tsirkin (4):
  pci: disable msi/msix at probe time
  pci: don't disable msi/msix at shutdown
  pci: make msi/msix shutdown functions static
  virtio_pci: drop msi_off on probe

 include/linux/pci.h                | 4 ----
 drivers/pci/msi.c                  | 4 ++--
 drivers/pci/pci-driver.c           | 8 ++++++--
 drivers/virtio/virtio_pci_common.c | 3 ---
 4 files changed, 8 insertions(+), 11 deletions(-)

-- 
MST

[PATCH RFC 1/4] pci: disable msi/msix at probe time

[Michael S. Tsirkin]

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@gmail.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Fam Zheng <famz@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 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..dac6d47 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(dev);
 	rc = pci_drv->probe(pci_dev, ddi->id);
 	if (!rc)
 		return rc;
-- 
MST

Re: [PATCH RFC 1/4] pci: disable msi/msix at probe time

[Michael S. Tsirkin]

On Mon, Mar 16, 2015 at 06:20:27PM +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@gmail.com>
> Cc: Ulrich Obergfell <uobergfe@redhat.com>
> Cc: Fam Zheng <famz@redhat.com>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  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..dac6d47 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(dev);

should be
	pci_msi_off(pci_dev);

obviously.

Which likely means I pushed a wrong tree
to the test machine again, so this wasn't
tested as I thought it is :(

I'll re-test and repost day after tomorrow,
Fam, can you tweak this manually when you are testing?
I don't want to spam the list.

>  	rc = pci_drv->probe(pci_dev, ddi->id);
>  	if (!rc)
>  		return rc;
> -- 
> MST
> 

[PATCH RFC 2/4] pci: don't disable msi/msix at shutdown

[Michael S. Tsirkin]

This partially reverts commit d52877c7b1afb8c37ebe17e2005040b79cb618b0:
	"pci/irq: let pci_device_shutdown to call pci_msi_shutdown v2"

It's un-necessary now that we disable msi at start, and it actually
turns out to cause problems: some device drivers don't register a level
interrupt handler when they detect msi/msix capability, switching off
msi while device is going causes device to assert a level interrupt
which is never de-asserted, causing a kernel hang.

In particular, this was observed with virtio.

Cc: Yinghai Lu <yhlu.kernel.send@gmail.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reported-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/pci/pci-driver.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index dac6d47..4746f93 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -456,8 +456,6 @@ static void pci_device_shutdown(struct device *dev)
 
 	if (drv && drv->shutdown)
 		drv->shutdown(pci_dev);
-	pci_msi_shutdown(pci_dev);
-	pci_msix_shutdown(pci_dev);
 
 #ifdef CONFIG_KEXEC
 	/*
-- 
MST

[PATCH RFC 3/4] pci: make msi/msix shutdown functions static

[Michael S. Tsirkin]

pci_msi_shutdown and pci_msix_shutdown are now internal to msi.c, drop
them from header and make them static.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/linux/pci.h | 4 ----
 drivers/pci/msi.c   | 4 ++--
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 211e9da..a34df45 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1209,11 +1209,9 @@ struct msix_entry {
 
 #ifdef CONFIG_PCI_MSI
 int pci_msi_vec_count(struct pci_dev *dev);
-void pci_msi_shutdown(struct pci_dev *dev);
 void pci_disable_msi(struct pci_dev *dev);
 int pci_msix_vec_count(struct pci_dev *dev);
 int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec);
-void pci_msix_shutdown(struct pci_dev *dev);
 void pci_disable_msix(struct pci_dev *dev);
 void pci_restore_msi_state(struct pci_dev *dev);
 int pci_msi_enabled(void);
@@ -1237,13 +1235,11 @@ static inline int pci_enable_msix_exact(struct pci_dev *dev,
 }
 #else
 static inline int pci_msi_vec_count(struct pci_dev *dev) { return -ENOSYS; }
-static inline void pci_msi_shutdown(struct pci_dev *dev) { }
 static inline void pci_disable_msi(struct pci_dev *dev) { }
 static inline int pci_msix_vec_count(struct pci_dev *dev) { return -ENOSYS; }
 static inline int pci_enable_msix(struct pci_dev *dev,
 				  struct msix_entry *entries, int nvec)
 { return -ENOSYS; }
-static inline void pci_msix_shutdown(struct pci_dev *dev) { }
 static inline void pci_disable_msix(struct pci_dev *dev) { }
 static inline void pci_restore_msi_state(struct pci_dev *dev) { }
 static inline int pci_msi_enabled(void) { return 0; }
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index c3e7dfc..0e037af 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -908,7 +908,7 @@ int pci_msi_vec_count(struct pci_dev *dev)
 }
 EXPORT_SYMBOL(pci_msi_vec_count);
 
-void pci_msi_shutdown(struct pci_dev *dev)
+static void pci_msi_shutdown(struct pci_dev *dev)
 {
 	struct msi_desc *desc;
 	u32 mask;
@@ -1014,7 +1014,7 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
 }
 EXPORT_SYMBOL(pci_enable_msix);
 
-void pci_msix_shutdown(struct pci_dev *dev)
+static void pci_msix_shutdown(struct pci_dev *dev)
 {
 	struct msi_desc *entry;
 
-- 
MST

[PATCH RFC 4/4] virtio_pci: drop msi_off on probe

[Michael S. Tsirkin]

pci core now disables msi on probe automatically,
drop this from device-specific code.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/virtio/virtio_pci_common.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index a0723d1..f506571 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -501,9 +501,6 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
 	INIT_LIST_HEAD(&vp_dev->virtqueues);
 	spin_lock_init(&vp_dev->lock);
 
-	/* Disable MSI/MSIX to bring device to a known good state. */
-	pci_msi_off(pci_dev);
-
 	/* enable the device */
 	rc = pci_enable_device(pci_dev);
 	if (rc)
-- 
MST