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Subject[PATCH 2/3] x86, MSI: Allocate as many multiple IRQs as requested
When multiple MSIs are enabled with pci_enable_msi_block() the number of
allocated IRQs 'nvec' is rounded up to the nearest value of power of two.
That could lead to a condition when number of requested and used IRQs is
less than number of actually allocated IRQs.

This fix introduces 'msi_desc::nvec' field to address the above issue -
when non-zero, it holds the number of allocated IRQs. Otherwise, the old
method is used.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
---
arch/x86/kernel/apic/io_apic.c | 16 +++++++---------
drivers/pci/msi.c | 10 ++++++++--
include/linux/msi.h | 1 +
3 files changed, 16 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index f083049..5a5c92b 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3107,16 +3107,12 @@ static inline void destroy_irqs(unsigned int irq, unsigned int count)
}

static inline int
-can_create_pow_of_two_irqs(unsigned int from, unsigned int count)
+can_create_irqs(unsigned int from, unsigned int count)
{
- if ((count > 1) && (count % 2))
- return -EINVAL;
-
- for (; count; count = count / 2) {
+ for (; count; count = count - 1) {
if (!irq_can_alloc_irqs(from, count))
return count;
}
-
return -ENOSPC;
}

@@ -3298,8 +3294,7 @@ int setup_msi_irqs(struct pci_dev *dev, int nvec)
if (nvec > 1 && !irq_remapping_enabled)
return 1;

- nvec = __roundup_pow_of_two(nvec);
- ret = can_create_pow_of_two_irqs(nr_irqs_gsi, nvec);
+ ret = can_create_irqs(nr_irqs_gsi, nvec);
if (ret != nvec)
return ret;

@@ -3307,11 +3302,13 @@ int setup_msi_irqs(struct pci_dev *dev, int nvec)
msidesc = list_entry(dev->msi_list.next, struct msi_desc, list);
WARN_ON(msidesc->irq);
WARN_ON(msidesc->msi_attrib.multiple);
+ WARN_ON(msidesc->nvec);

node = dev_to_node(&dev->dev);
irq = create_irqs(nr_irqs_gsi, nvec, node);
if (irq == 0)
return -ENOSPC;
+ msidesc->nvec = nvec;

if (!irq_remapping_enabled) {
ret = setup_msi_irq(dev, msidesc, irq, 0);
@@ -3320,7 +3317,7 @@ int setup_msi_irqs(struct pci_dev *dev, int nvec)
return 0;
}

- msidesc->msi_attrib.multiple = ilog2(nvec);
+ msidesc->msi_attrib.multiple = ilog2(__roundup_pow_of_two(nvec));
for (sub_handle = 0; sub_handle < nvec; sub_handle++) {
if (!sub_handle) {
index = msi_alloc_remapped_irq(dev, irq, nvec);
@@ -3348,6 +3345,7 @@ error:
*/
msidesc->irq = 0;
msidesc->msi_attrib.multiple = 0;
+ msidesc->nvec = 0;

return ret;
}
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index a825d78..f0752d1 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -79,7 +79,10 @@ void default_teardown_msi_irqs(struct pci_dev *dev)
int i, nvec;
if (entry->irq == 0)
continue;
- nvec = 1 << entry->msi_attrib.multiple;
+ if (entry->nvec)
+ nvec = entry->nvec;
+ else
+ nvec = 1 << entry->msi_attrib.multiple;
for (i = 0; i < nvec; i++)
arch_teardown_msi_irq(entry->irq + i);
}
@@ -336,7 +339,10 @@ static void free_msi_irqs(struct pci_dev *dev)
int i, nvec;
if (!entry->irq)
continue;
- nvec = 1 << entry->msi_attrib.multiple;
+ if (entry->nvec)
+ nvec = entry->nvec;
+ else
+ nvec = 1 << entry->msi_attrib.multiple;
for (i = 0; i < nvec; i++)
BUG_ON(irq_has_action(entry->irq + i));
}
diff --git a/include/linux/msi.h b/include/linux/msi.h
index ce93a34..6f4dfba 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -35,6 +35,7 @@ struct msi_desc {

u32 masked; /* mask bits */
unsigned int irq;
+ unsigned int nvec;
struct list_head list;

union {
--
1.7.7.6

--
Regards,
Alexander Gordeev
agordeev@redhat.com


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