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PCI: vmd: White list for fast interrupt handlers

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commit a7f58b9ecf upstream.

Devices with slow interrupt handlers are significantly harming
performance when their interrupt vector is shared with a fast device.

Create a class code white list for devices with known fast interrupt
handlers and let all other devices share a single vector so that they
don't interfere with performance.

At the moment, only the NVM Express class code is on the list, but more
may be added if VMD users desire to use other low-latency devices in
these domains.

Signed-off-by: Keith Busch <keith.busch@intel.com>
[lorenzo.pieralisi@arm.com: changelog]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Jon Derrick: <jonathan.derrick@intel.com>
Cc: "Heitke, Kenneth" <kenneth.heitke@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Keith Busch
2018-11-13 11:12:41 -08:00
committed by Greg Kroah-Hartman
parent a06dfc8d5e
commit a5d415583c
1 changed files with 12 additions and 1 deletions
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drivers/pci/controller/vmd.c
+12 -1
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@@ -197,9 +197,20 @@ static struct vmd_irq_list *vmd_next_irq(struct vmd_dev *vmd, struct msi_desc *d
int i, best = 1;
unsigned long flags;
if (pci_is_bridge(msi_desc_to_pci_dev(desc)) || vmd->msix_count == 1)
if (vmd->msix_count == 1)
return &vmd->irqs[0];
/*
* White list for fast-interrupt handlers. All others will share the
* "slow" interrupt vector.
*/
switch (msi_desc_to_pci_dev(desc)->class) {
case PCI_CLASS_STORAGE_EXPRESS:
break;
default:
return &vmd->irqs[0];
}
raw_spin_lock_irqsave(&list_lock, flags);
for (i = 1; i < vmd->msix_count; i++)
if (vmd->irqs[i].count < vmd->irqs[best].count)