linux-kernel - Re: [PATCH] Xen PCI fronted fixes for 2.6.39

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Date:	Fri, 18 Feb 2011 09:22:30 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	linux-kernel@...r.kernel.org,
	Ian Campbell <Ian.Campbell@...citrix.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	xen-devel@...ts.xensource.com,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Konrad Rzeszutek Wilk <konrad@...nel.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: Re: [PATCH] Xen PCI fronted fixes for 2.6.39

On Wed, Feb 16, 2011 at 05:17:15PM -0500, Konrad Rzeszutek Wilk wrote:
> I am proposing these three patches for 2.6.39.
> 
> The first is to take advantage of the new method of requesting
> a Linux IRQ and providing the Xen PIRQ value. The second
> makes it possible for a PV guest to bootup if the backend has provided
> incorrect values. [*2]
> 
> Lastly, the third is to remove deprecated code.

And lets add one more:

>From e4e8523b1d374a3f4276c34e6d017b425ce0d1ae Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Date: Thu, 17 Feb 2011 16:12:51 -0500
Subject: [PATCH 5/5] pci/xen: When free-ing MSI-X/MSI irq->desc also use generic code.

This code path is only run when an MSI/MSI-X PCI device is passed
in to PV DomU.

In 2.6.37 time-frame we over-wrote the default cleanup handler for
MSI/MSI-X irq->desc to be "xen_teardown_msi_irqs". That function
calls the the xen-pcifront driver which can tell the backend to
cleanup/take back the MSI/MSI-X device.

However, we forgot to continue the process of free-ing the MSI/MSI-X
device resources (irq->desc) in the PV domU side. Which is what
the default cleanup handler "default_teardown_msi_irqs" did.

Hence we would leak IRQ descriptors.

Without this patch, doing "rmmod igbvf;modprobe igbvf" multiple
times ends with abandoned IRQ descriptors:

 28:          5  xen-pirq-pcifront-msi-x
 29:          8  xen-pirq-pcifront-msi-x
...
130:         10  xen-pirq-pcifront-msi-x

with the end result of running out of IRQ descriptors.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
 arch/x86/pci/xen.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 30fdd09..57afd1d 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -193,6 +193,9 @@ static void xen_teardown_msi_irqs(struct pci_dev *dev)
 		xen_pci_frontend_disable_msix(dev);
 	else
 		xen_pci_frontend_disable_msi(dev);
+
+	/* Free the IRQ's and the msidesc using the generic code. */
+	default_teardown_msi_irqs(dev);
 }
 
 static void xen_teardown_msi_irq(unsigned int irq)
-- 
1.7.1

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