diff mbox series

[2/5] xen: Set platform PCI device INTX affinity to CPU0

Message ID 20201224115323.3540130-3-dwmw2@infradead.org (mailing list archive)
State Superseded
Headers show
Series Xen INTX/GSI event channel delivery fixes | expand

Commit Message

David Woodhouse Dec. 24, 2020, 11:53 a.m. UTC 
From: David Woodhouse <dwmw@amazon.co.uk>

With INTX or GSI delivery, Xen uses the event channel structures of CPU0.

If the interrupt gets handled by Linux on a different CPU, then no events
are seen as pending. Rather than introducing locking to allow other CPUs
to process CPU0's events, just ensure that the PCI interrupts happens
only on CPU0.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 drivers/xen/platform-pci.c | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Boris Ostrovsky Jan. 4, 2021, 4:42 p.m. UTC | #1 
On 12/24/20 6:53 AM, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
>
> With INTX or GSI delivery, Xen uses the event channel structures of CPU0.
>
> If the interrupt gets handled by Linux on a different CPU, then no events
> are seen as pending. Rather than introducing locking to allow other CPUs
> to process CPU0's events, just ensure that the PCI interrupts happens
> only on CPU0.
>
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
diff mbox series

Patch

diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
index 9db557b76511..18f0ed8b1f93 100644
--- a/drivers/xen/platform-pci.c
+++ b/drivers/xen/platform-pci.c
@@ -132,6 +132,13 @@  static int platform_pci_probe(struct pci_dev *pdev,
 			dev_warn(&pdev->dev, "request_irq failed err=%d\n", ret);
 			goto out;
 		}
+		/*
+		 * It doesn't strictly *have* to run on CPU0 but it sure
+		 * as hell better process the event channel ports delivered
+		 * to CPU0.
+		 */
+		irq_set_affinity(pdev->irq, cpumask_of(0));
+
 		callback_via = get_callback_via(pdev);
 		ret = xen_set_callback_via(callback_via);
 		if (ret) {