[PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Mitch Williams]

This patch fixes a kernel bug which is triggered when using the
irqbalance daemon with MSI-X hardware.

Because both MSI-X interrupt messages and MSI-X table writes are posted,
it's possible for them to cross while in-flight.  This results in
interrupts being received long after the kernel thinks they're disabled,
and in interrupts being sent to stale vectors after rebalancing.

This patch performs a read flush after writes to the MSI-X table for
mask/unmask and rebalancing operations.

This patch has been validated with (unreleased) network hardware which
uses MSI-X.

Revised with input from Eric Biederman.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>

diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/i386/kernel/io_apic.c linux-2.6.21-rc5/arch/i386/kernel/io_apic.c
--- linux-2.6.21-rc5-clean/arch/i386/kernel/io_apic.c	2007-03-28 10:05:22.000000000 -0700
+++ linux-2.6.21-rc5/arch/i386/kernel/io_apic.c	2007-03-28 10:19:14.000000000 -0700
@@ -2584,6 +2584,7 @@ static void set_msi_irq_affinity(unsigne
 	msg.address_lo |= MSI_ADDR_DEST_ID(dest);
 
 	write_msi_msg(irq, &msg);
+	msix_flush_writes(irq);
 	irq_desc[irq].affinity = mask;
 }
 #endif /* CONFIG_SMP */
diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/ia64/kernel/msi_ia64.c linux-2.6.21-rc5/arch/ia64/kernel/msi_ia64.c
--- linux-2.6.21-rc5-clean/arch/ia64/kernel/msi_ia64.c	2007-03-28 10:05:22.000000000 -0700
+++ linux-2.6.21-rc5/arch/ia64/kernel/msi_ia64.c	2007-03-28 09:34:27.000000000 -0700
@@ -60,6 +60,7 @@ static void ia64_set_msi_irq_affinity(un
 	msg.address_lo = addr;
 
 	write_msi_msg(irq, &msg);
+	msix_flush_writes(irq);
 	irq_desc[irq].affinity = cpu_mask;
 }
 #endif /* CONFIG_SMP */
diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/ia64/sn/kernel/msi_sn.c linux-2.6.21-rc5/arch/ia64/sn/kernel/msi_sn.c
--- linux-2.6.21-rc5-clean/arch/ia64/sn/kernel/msi_sn.c	2007-03-28 10:05:22.000000000 -0700
+++ linux-2.6.21-rc5/arch/ia64/sn/kernel/msi_sn.c	2007-03-28 09:34:06.000000000 -0700
@@ -204,6 +204,7 @@ static void sn_set_msi_irq_affinity(unsi
 	msg.address_lo = (u32)(bus_addr & 0x00000000ffffffff);
 
 	write_msi_msg(irq, &msg);
+	msix_flush_writes(irq);
 	irq_desc[irq].affinity = cpu_mask;
 }
 #endif /* CONFIG_SMP */
diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/x86_64/kernel/io_apic.c linux-2.6.21-rc5/arch/x86_64/kernel/io_apic.c
--- linux-2.6.21-rc5-clean/arch/x86_64/kernel/io_apic.c	2007-03-28 10:05:22.000000000 -0700
+++ linux-2.6.21-rc5/arch/x86_64/kernel/io_apic.c	2007-03-28 10:18:52.000000000 -0700
@@ -1956,6 +1956,7 @@ static void set_msi_irq_affinity(unsigne
 	msg.address_lo |= MSI_ADDR_DEST_ID(dest);
 
 	write_msi_msg(irq, &msg);
+	msix_flush_writes(irq);
 	irq_desc[irq].affinity = mask;
 }
 #endif /* CONFIG_SMP */
diff -urpN -X dontdiff linux-2.6.21-rc5-clean/drivers/pci/msi.c linux-2.6.21-rc5/drivers/pci/msi.c
--- linux-2.6.21-rc5-clean/drivers/pci/msi.c	2007-03-28 10:05:24.000000000 -0700
+++ linux-2.6.21-rc5/drivers/pci/msi.c	2007-03-28 09:21:34.000000000 -0700
@@ -68,6 +68,29 @@ static void msix_set_enable(struct pci_d
 	}
 }
 
+void msix_flush_writes(unsigned int irq)
+{
+	struct msi_desc *entry;
+
+	entry = get_irq_msi(irq);
+	BUG_ON(!entry || !entry->dev);
+	switch (entry->msi_attrib.type) {
+	case PCI_CAP_ID_MSI:
+		/* nothing to do */
+		break;
+	case PCI_CAP_ID_MSIX:
+	{
+		int offset = entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
+			PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET;
+		readl(entry->mask_base + offset);
+		break;
+	}
+	default:
+		BUG();
+		break;
+	}
+}
+
 static void msi_set_mask_bit(unsigned int irq, int flag)
 {
 	struct msi_desc *entry;
@@ -186,11 +209,13 @@ void write_msi_msg(unsigned int irq, str
 void mask_msi_irq(unsigned int irq)
 {
 	msi_set_mask_bit(irq, 1);
+	msix_flush_writes(irq);
 }
 
 void unmask_msi_irq(unsigned int irq)
 {
 	msi_set_mask_bit(irq, 0);
+	msix_flush_writes(irq);
 }
 
 static int msi_free_irq(struct pci_dev* dev, int irq);
diff -urpN -X dontdiff linux-2.6.21-rc5-clean/include/linux/msi.h linux-2.6.21-rc5/include/linux/msi.h
--- linux-2.6.21-rc5-clean/include/linux/msi.h	2007-03-28 10:05:25.000000000 -0700
+++ linux-2.6.21-rc5/include/linux/msi.h	2007-03-28 09:21:51.000000000 -0700
@@ -12,6 +12,7 @@ extern void mask_msi_irq(unsigned int ir
 extern void unmask_msi_irq(unsigned int irq);
 extern void read_msi_msg(unsigned int irq, struct msi_msg *msg);
 extern void write_msi_msg(unsigned int irq, struct msi_msg *msg);
+extern void msix_flush_writes(unsigned int irq);
 
 struct msi_desc {
 	struct {

Re: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Eric W. Biederman]

Mitch Williams <mitch.a.williams@intel.com> writes:

> This patch fixes a kernel bug which is triggered when using the
> irqbalance daemon with MSI-X hardware.
>
> Because both MSI-X interrupt messages and MSI-X table writes are posted,
> it's possible for them to cross while in-flight.  This results in
> interrupts being received long after the kernel thinks they're disabled,
> and in interrupts being sent to stale vectors after rebalancing.
>
> This patch performs a read flush after writes to the MSI-X table for
> mask/unmask and rebalancing operations.
>
> This patch has been validated with (unreleased) network hardware which
> uses MSI-X.
>
> Revised with input from Eric Biederman.

Do we still need the flush the set affinity routines?
Shouldn't flush in mask and unmask should now be enough?


>
> Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
>
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/i386/kernel/io_apic.c
> linux-2.6.21-rc5/arch/i386/kernel/io_apic.c
> --- linux-2.6.21-rc5-clean/arch/i386/kernel/io_apic.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/i386/kernel/io_apic.c 2007-03-28 10:19:14.000000000
> -0700
> @@ -2584,6 +2584,7 @@ static void set_msi_irq_affinity(unsigne
>  	msg.address_lo |= MSI_ADDR_DEST_ID(dest);
>  
>  	write_msi_msg(irq, &msg);
> +	msix_flush_writes(irq);
>  	irq_desc[irq].affinity = mask;
>  }
>  #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/ia64/kernel/msi_ia64.c
> linux-2.6.21-rc5/arch/ia64/kernel/msi_ia64.c
> --- linux-2.6.21-rc5-clean/arch/ia64/kernel/msi_ia64.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/ia64/kernel/msi_ia64.c 2007-03-28 09:34:27.000000000
> -0700
> @@ -60,6 +60,7 @@ static void ia64_set_msi_irq_affinity(un
>  	msg.address_lo = addr;
>  
>  	write_msi_msg(irq, &msg);
> +	msix_flush_writes(irq);
>  	irq_desc[irq].affinity = cpu_mask;
>  }
>  #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/ia64/sn/kernel/msi_sn.c
> linux-2.6.21-rc5/arch/ia64/sn/kernel/msi_sn.c
> --- linux-2.6.21-rc5-clean/arch/ia64/sn/kernel/msi_sn.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/ia64/sn/kernel/msi_sn.c 2007-03-28 09:34:06.000000000
> -0700
> @@ -204,6 +204,7 @@ static void sn_set_msi_irq_affinity(unsi
>  	msg.address_lo = (u32)(bus_addr & 0x00000000ffffffff);
>  
>  	write_msi_msg(irq, &msg);
> +	msix_flush_writes(irq);
>  	irq_desc[irq].affinity = cpu_mask;
>  }
>  #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/arch/x86_64/kernel/io_apic.c
> linux-2.6.21-rc5/arch/x86_64/kernel/io_apic.c
> --- linux-2.6.21-rc5-clean/arch/x86_64/kernel/io_apic.c 2007-03-28
> 10:05:22.000000000 -0700
> +++ linux-2.6.21-rc5/arch/x86_64/kernel/io_apic.c 2007-03-28 10:18:52.000000000
> -0700
> @@ -1956,6 +1956,7 @@ static void set_msi_irq_affinity(unsigne
>  	msg.address_lo |= MSI_ADDR_DEST_ID(dest);
>  
>  	write_msi_msg(irq, &msg);
> +	msix_flush_writes(irq);
>  	irq_desc[irq].affinity = mask;
>  }
>  #endif /* CONFIG_SMP */
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/drivers/pci/msi.c
> linux-2.6.21-rc5/drivers/pci/msi.c
> --- linux-2.6.21-rc5-clean/drivers/pci/msi.c 2007-03-28 10:05:24.000000000 -0700
> +++ linux-2.6.21-rc5/drivers/pci/msi.c	2007-03-28 09:21:34.000000000 -0700
> @@ -68,6 +68,29 @@ static void msix_set_enable(struct pci_d
>  	}
>  }
>  
> +void msix_flush_writes(unsigned int irq)
> +{
> +	struct msi_desc *entry;
> +
> +	entry = get_irq_msi(irq);
> +	BUG_ON(!entry || !entry->dev);
> +	switch (entry->msi_attrib.type) {
> +	case PCI_CAP_ID_MSI:
> +		/* nothing to do */
> +		break;
> +	case PCI_CAP_ID_MSIX:
> +	{
> +		int offset = entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
> +			PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET;
> +		readl(entry->mask_base + offset);
> +		break;
> +	}
> +	default:
> +		BUG();
> +		break;
> +	}
> +}
> +
>  static void msi_set_mask_bit(unsigned int irq, int flag)
>  {
>  	struct msi_desc *entry;
> @@ -186,11 +209,13 @@ void write_msi_msg(unsigned int irq, str
>  void mask_msi_irq(unsigned int irq)
>  {
>  	msi_set_mask_bit(irq, 1);
> +	msix_flush_writes(irq);
>  }
>  
>  void unmask_msi_irq(unsigned int irq)
>  {
>  	msi_set_mask_bit(irq, 0);
> +	msix_flush_writes(irq);
>  }
>  
>  static int msi_free_irq(struct pci_dev* dev, int irq);
> diff -urpN -X dontdiff linux-2.6.21-rc5-clean/include/linux/msi.h
> linux-2.6.21-rc5/include/linux/msi.h
> --- linux-2.6.21-rc5-clean/include/linux/msi.h 2007-03-28 10:05:25.000000000
> -0700
> +++ linux-2.6.21-rc5/include/linux/msi.h 2007-03-28 09:21:51.000000000 -0700
> @@ -12,6 +12,7 @@ extern void mask_msi_irq(unsigned int ir
>  extern void unmask_msi_irq(unsigned int irq);
>  extern void read_msi_msg(unsigned int irq, struct msi_msg *msg);
>  extern void write_msi_msg(unsigned int irq, struct msi_msg *msg);
> +extern void msix_flush_writes(unsigned int irq);
>  
>  struct msi_desc {
>  	struct {

Re: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Chuck Ebbert]

Mitch Williams wrote:
> This patch fixes a kernel bug which is triggered when using the
> irqbalance daemon with MSI-X hardware.
> 
> Because both MSI-X interrupt messages and MSI-X table writes are posted,
> it's possible for them to cross while in-flight.  This results in
> interrupts being received long after the kernel thinks they're disabled,
> and in interrupts being sent to stale vectors after rebalancing.
> 
> This patch performs a read flush after writes to the MSI-X table for
> mask/unmask and rebalancing operations.
> 
> This patch has been validated with (unreleased) network hardware which
> uses MSI-X.
> 
> Revised with input from Eric Biederman.
> 
> Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
> 

Are you going to post one for 2.6.20 as well? Some people might be
interested...

Re: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Randy Dunlap]

On Thu, 29 Mar 2007 13:25:34 -0400 Chuck Ebbert wrote:

> 
> Are you going to post one for 2.6.20 as well? Some people might be
> interested...

Please don't drop cc:s.

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

RE: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Williams, Mitch A]

Eric W. Biederman wrote:

>Do we still need the flush the set affinity routines?
>Shouldn't flush in mask and unmask should now be enough?

Yeah, I think you're right.  I've removed that call, and 
we're running some basic validation on the change.  I'll
post a new patch tomorrow AM.
-Mitch

RE: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Williams, Mitch A]

Chuck Ebbert wrote:
>Are you going to post one for 2.6.20 as well? Some people might be
>interested...

The first time I posted this patch, Greg KH indicated that he thought
it was too intrusive to add to -stable, especially considering that
our MSI-X capable hardware isn't in the field yet.

So the answer to your question is, "probably not".
-Mitch

Re: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Chuck Ebbert]

Williams, Mitch A wrote:
> Chuck Ebbert wrote:
>> Are you going to post one for 2.6.20 as well? Some people might be
>> interested...
> 
> The first time I posted this patch, Greg KH indicated that he thought
> it was too intrusive to add to -stable, especially considering that
> our MSI-X capable hardware isn't in the field yet.
> 
> So the answer to your question is, "probably not".

So it's not useful in 2.6.20 for anything that's available today, from
any vendor? We can put it in Fedora if you think it is.

Re: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Eric W. Biederman]

"Williams, Mitch A" <mitch.a.williams@intel.com> writes:

> Chuck Ebbert wrote:
>>Are you going to post one for 2.6.20 as well? Some people might be
>>interested...
>
> The first time I posted this patch, Greg KH indicated that he thought
> it was too intrusive to add to -stable, especially considering that
> our MSI-X capable hardware isn't in the field yet.

There is MSI-X capable hardware supported by the kernel in 2.6.20.

The last version of your patch with the code removed from the set_affinity
path is not very intrusive at all, as it just touches msi.c

Eric

Re: [PATCH 2.6.21-rc5] MSI: read-flush MSI-X table (rev 2)

[Eric W. Biederman]

"Williams, Mitch A" <mitch.a.williams@intel.com> writes:

> Chuck Ebbert wrote:
>>Are you going to post one for 2.6.20 as well? Some people might be
>>interested...
>
> The first time I posted this patch, Greg KH indicated that he thought
> it was too intrusive to add to -stable, especially considering that
> our MSI-X capable hardware isn't in the field yet.

There is MSI-X capable hardware supported by the kernel in 2.6.20.

The last version of your patch with the code removed from the set_affinity
path is not very intrusive at all, as it just touches msi.c

Eric