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* [PATCH] vfio/pci: make MSI handling optional
@ 2014-10-09  8:40 Arnd Bergmann
  2014-10-13  8:50 ` Alex Williamson
  0 siblings, 1 reply; 5+ messages in thread
From: Arnd Bergmann @ 2014-10-09  8:40 UTC (permalink / raw)
  To: Alex Williamson
  Cc: kvm, Gavin Shan, Wen Xiong, linux-kernel, linux-arm-kernel

A recent bug fix to the MSIx handling in vfio added references
to functions that may not be defined if MSI is disabled in the kernel,
resulting in this link error:

drivers/built-in.o: In function `vfio_msi_set_vector_signal':
:(.text+0x450808): undefined reference to `get_cached_msi_msg'
:(.text+0x45080c): undefined reference to `write_msi_msg'

>From what I can tell, all the MSI specific ioctl handling can
be made optional in this case, which also reduces the code size
for the vfo driver. This patches does so using a build-time
IS_ENABLED() check, which leaves all the build coverage testing
present but avoids the link error.

A side-effect of this is that the driver now returns -ENOTTY instead
of -EINVAL if user space calls VFIO_PCI_MSI_IRQ_INDEX on a kernel
without MSI support, which seems to be the best behavior, but
the approach could easily be changed if we want to preserve the
existing behavior for compatibility reasons.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b8f02af096b1 ("vfio/pci: Restore MSIx message prior to enabling")
---
Found using randconfig build testing on ARM.

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 553212f037c3..1117f96b8556 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -827,6 +827,9 @@ int vfio_pci_set_irqs_ioctl(struct vfio_pci_device *vdev, uint32_t flags,
 		break;
 	case VFIO_PCI_MSI_IRQ_INDEX:
 	case VFIO_PCI_MSIX_IRQ_INDEX:
+		if (!IS_ENABLED(CONFIG_PCI_MSI))
+			break;
+
 		switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
 		case VFIO_IRQ_SET_ACTION_MASK:
 		case VFIO_IRQ_SET_ACTION_UNMASK:


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* Re: [PATCH] vfio/pci: make MSI handling optional
  2014-10-09  8:40 [PATCH] vfio/pci: make MSI handling optional Arnd Bergmann
@ 2014-10-13  8:50 ` Alex Williamson
  2014-10-13 11:02   ` Arnd Bergmann
  2017-02-14 21:53   ` [PATCH] genirq/msi: add stubs for get_cached_msi_msg/pci_write_msi_msg Arnd Bergmann
  0 siblings, 2 replies; 5+ messages in thread
From: Alex Williamson @ 2014-10-13  8:50 UTC (permalink / raw)
  To: Arnd Bergmann; +Cc: kvm, Gavin Shan, Wen Xiong, linux-kernel, linux-arm-kernel

On Thu, 2014-10-09 at 10:40 +0200, Arnd Bergmann wrote:
> A recent bug fix to the MSIx handling in vfio added references
> to functions that may not be defined if MSI is disabled in the kernel,
> resulting in this link error:
> 
> drivers/built-in.o: In function `vfio_msi_set_vector_signal':
> :(.text+0x450808): undefined reference to `get_cached_msi_msg'
> :(.text+0x45080c): undefined reference to `write_msi_msg'
> 
> From what I can tell, all the MSI specific ioctl handling can
> be made optional in this case, which also reduces the code size
> for the vfo driver. This patches does so using a build-time
> IS_ENABLED() check, which leaves all the build coverage testing
> present but avoids the link error.
> 
> A side-effect of this is that the driver now returns -ENOTTY instead
> of -EINVAL if user space calls VFIO_PCI_MSI_IRQ_INDEX on a kernel
> without MSI support, which seems to be the best behavior, but
> the approach could easily be changed if we want to preserve the
> existing behavior for compatibility reasons.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: b8f02af096b1 ("vfio/pci: Restore MSIx message prior to enabling")
> ---

Why wouldn't we handle this with stubs for `get_cached_msi_msg' and
`write_msi_msg'?  We're really not talking about much code that might
get removed by the compiler with this static branch and and it seems
like a rather non-standard mechanism.  The count of MSI/X IRQs
advertised to the user should be zero without CONFIG_MSI and later range
checks would prevent calls to
these functions for invalid indexes, so it's a bit of a random test in
the code flow.  Thanks,

Alex

> Found using randconfig build testing on ARM.
> 
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 553212f037c3..1117f96b8556 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -827,6 +827,9 @@ int vfio_pci_set_irqs_ioctl(struct vfio_pci_device *vdev, uint32_t flags,
>  		break;
>  	case VFIO_PCI_MSI_IRQ_INDEX:
>  	case VFIO_PCI_MSIX_IRQ_INDEX:
> +		if (!IS_ENABLED(CONFIG_PCI_MSI))
> +			break;
> +
>  		switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
>  		case VFIO_IRQ_SET_ACTION_MASK:
>  		case VFIO_IRQ_SET_ACTION_UNMASK:
> 




^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH] vfio/pci: make MSI handling optional
  2014-10-13  8:50 ` Alex Williamson
@ 2014-10-13 11:02   ` Arnd Bergmann
  2017-02-14 21:53   ` [PATCH] genirq/msi: add stubs for get_cached_msi_msg/pci_write_msi_msg Arnd Bergmann
  1 sibling, 0 replies; 5+ messages in thread
From: Arnd Bergmann @ 2014-10-13 11:02 UTC (permalink / raw)
  To: linux-arm-kernel
  Cc: Alex Williamson, Wen Xiong, Gavin Shan, kvm, linux-kernel

On Monday 13 October 2014 02:50:08 Alex Williamson wrote:
> 
> Why wouldn't we handle this with stubs for `get_cached_msi_msg' and
> `write_msi_msg'?  We're really not talking about much code that might
> get removed by the compiler with this static branch and and it seems
> like a rather non-standard mechanism.  The count of MSI/X IRQs
> advertised to the user should be zero without CONFIG_MSI and later range
> checks would prevent calls to
> these functions for invalid indexes, so it's a bit of a random test in
> the code flow.  Thanks,
> 

That's fine with me too.

	Arnd

^ permalink raw reply	[flat|nested] 5+ messages in thread
* [PATCH] genirq/msi: add stubs for get_cached_msi_msg/pci_write_msi_msg
@ 2017-02-14 21:53   ` Arnd Bergmann
  2017-02-16 14:34     ` [tip:irq/core] genirq/msi: Add " tip-bot for Arnd Bergmann
  0 siblings, 1 reply; 5+ messages in thread
From: Arnd Bergmann @ 2017-02-14 21:53 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: Alex Williamson, Arnd Bergmann, Marc Zyngier, Bjorn Helgaas,
	Bart Van Assche, linux-kernel

A bug fix to the MSIx handling in vfio added references to functions
that may not be defined if MSI is disabled in the kernel, resulting in
this link error:

drivers/built-in.o: In function `vfio_msi_set_vector_signal':
:(.text+0x450808): undefined reference to `get_cached_msi_msg'
:(.text+0x45080c): undefined reference to `write_msi_msg'

As suggested by Alex Williamson, this adds stub implementations for
get_cached_msi_msg() and pci_write_msi_msg().

In case this bugfix gets backported, please note that the #ifdef
has changed over time, originally both functions were implemented
in drivers/pci/msi.c and controlled by CONFIG_PCI_MSI, while nowadays
get_cached_msi_msg() is part of the generic MSI support and can be
used without PCI.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b8f02af096b1 ("vfio/pci: Restore MSIx message prior to enabling")
Link: https://lkml.org/lkml/2014/10/13/124
---
I had a workaround for this hidden in my randconfig tree but have
now stumbled over it again, sorry for not following up a couple of years
earlier.
---
 include/linux/msi.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index 0db320b7bb15..a83b84ff70e5 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -17,7 +17,13 @@ struct msi_desc;
 struct pci_dev;
 struct platform_msi_priv_data;
 void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
+#ifdef CONFIG_GENERIC_MSI_IRQ
 void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);
+#else
+static inline void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg)
+{
+}
+#endif
 
 typedef void (*irq_write_msi_msg_t)(struct msi_desc *desc,
 				    struct msi_msg *msg);
@@ -116,11 +122,15 @@ struct msi_desc {
 
 struct pci_dev *msi_desc_to_pci_dev(struct msi_desc *desc);
 void *msi_desc_to_pci_sysdata(struct msi_desc *desc);
+void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg);
 #else /* CONFIG_PCI_MSI */
 static inline void *msi_desc_to_pci_sysdata(struct msi_desc *desc)
 {
 	return NULL;
 }
+static inline void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg)
+{
+}
 #endif /* CONFIG_PCI_MSI */
 
 struct msi_desc *alloc_msi_entry(struct device *dev, int nvec,
@@ -128,7 +138,6 @@ struct msi_desc *alloc_msi_entry(struct device *dev, int nvec,
 void free_msi_entry(struct msi_desc *entry);
 void __pci_read_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
 void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
-void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg);
 
 u32 __pci_msix_desc_mask_irq(struct msi_desc *desc, u32 flag);
 u32 __pci_msi_desc_mask_irq(struct msi_desc *desc, u32 mask, u32 flag);
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [tip:irq/core] genirq/msi: Add stubs for get_cached_msi_msg/pci_write_msi_msg
  2017-02-14 21:53   ` [PATCH] genirq/msi: add stubs for get_cached_msi_msg/pci_write_msi_msg Arnd Bergmann
@ 2017-02-16 14:34     ` tip-bot for Arnd Bergmann
  0 siblings, 0 replies; 5+ messages in thread
From: tip-bot for Arnd Bergmann @ 2017-02-16 14:34 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: bart.vanassche, hpa, mingo, bhelgaas, tglx, linux-kernel, arnd,
	alex.williamson, marc.zyngier

Commit-ID:  2f44e29cef006a4b0a4ecf7d4c5aac7d0fbb505c
Gitweb:     http://git.kernel.org/tip/2f44e29cef006a4b0a4ecf7d4c5aac7d0fbb505c
Author:     Arnd Bergmann <arnd@arndb.de>
AuthorDate: Tue, 14 Feb 2017 22:53:12 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 16 Feb 2017 15:32:19 +0100

genirq/msi: Add stubs for get_cached_msi_msg/pci_write_msi_msg

A bug fix to the MSIx handling in vfio added references to functions
that may not be defined if MSI is disabled in the kernel, resulting in
this link error:

drivers/built-in.o: In function `vfio_msi_set_vector_signal':
:(.text+0x450808): undefined reference to `get_cached_msi_msg'
:(.text+0x45080c): undefined reference to `write_msi_msg'

As suggested by Alex Williamson, add stub implementations for
get_cached_msi_msg() and pci_write_msi_msg().

In case this bugfix gets backported, please note that the #ifdef
has changed over time, originally both functions were implemented
in drivers/pci/msi.c and controlled by CONFIG_PCI_MSI, while nowadays
get_cached_msi_msg() is part of the generic MSI support and can be
used without PCI.

Fixes: b8f02af096b1 ("vfio/pci: Restore MSIx message prior to enabling")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Bart Van Assche <bart.vanassche@sandisk.com>
Link: http://lkml.kernel.org/r/1413190208.4202.34.camel@ul30vt.home
Link: http://lkml.kernel.org/r/20170214215343.3307861-1-arnd@arndb.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 include/linux/msi.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index 0db320b..a83b84f 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -17,7 +17,13 @@ struct msi_desc;
 struct pci_dev;
 struct platform_msi_priv_data;
 void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
+#ifdef CONFIG_GENERIC_MSI_IRQ
 void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);
+#else
+static inline void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg)
+{
+}
+#endif
 
 typedef void (*irq_write_msi_msg_t)(struct msi_desc *desc,
 				    struct msi_msg *msg);
@@ -116,11 +122,15 @@ struct msi_desc {
 
 struct pci_dev *msi_desc_to_pci_dev(struct msi_desc *desc);
 void *msi_desc_to_pci_sysdata(struct msi_desc *desc);
+void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg);
 #else /* CONFIG_PCI_MSI */
 static inline void *msi_desc_to_pci_sysdata(struct msi_desc *desc)
 {
 	return NULL;
 }
+static inline void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg)
+{
+}
 #endif /* CONFIG_PCI_MSI */
 
 struct msi_desc *alloc_msi_entry(struct device *dev, int nvec,
@@ -128,7 +138,6 @@ struct msi_desc *alloc_msi_entry(struct device *dev, int nvec,
 void free_msi_entry(struct msi_desc *entry);
 void __pci_read_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
 void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
-void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg);
 
 u32 __pci_msix_desc_mask_irq(struct msi_desc *desc, u32 flag);
 u32 __pci_msi_desc_mask_irq(struct msi_desc *desc, u32 mask, u32 flag);

^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-02-16 14:34 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-10-09  8:40 [PATCH] vfio/pci: make MSI handling optional Arnd Bergmann
2014-10-13  8:50 ` Alex Williamson
2014-10-13 11:02   ` Arnd Bergmann
2017-02-14 21:53   ` [PATCH] genirq/msi: add stubs for get_cached_msi_msg/pci_write_msi_msg Arnd Bergmann
2017-02-16 14:34     ` [tip:irq/core] genirq/msi: Add " tip-bot for Arnd Bergmann

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