From: AMEET M. PARANJAPE <aparanja@redhat.com>
Date: Tue, 31 Mar 2009 11:05:25 -0400
Subject: [ppc] return req#msi(-x) if request is larger
Message-id: 20090331150312.14954.99764.sendpatchset@squad5-lp1.lab.bos.redhat.com
O-Subject: [PATCH RHEL5.4 BZ492580 6/8]
Bugzilla: 492580
RH-Acked-by: David Howells <dhowells@redhat.com>

RHBZ#:
======
https://bugzilla.redhat.com/show_bug.cgi?id=492580

Description:
===========
If a driver asks for more MSIs than the devices "req#msi(-x)" property,
we currently return -ENOSPC. This doesn't give the driver any chance to
make a new request with a number that might work.

So if "req#msi(-x)" is less than the request, return its value. To be
100% safe, make sure we return an error if req_msi == 0.

RHEL Version Found:
================
RHEL 5.3

kABI Status:
============
No symbols were harmed.

Brew:
=====
Built on all platforms.
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1744271

Upstream Status:
================
http://git.kernel.org/?p=linux/kernel/git/benh/powerpc.git;a=commit;h=d523cc379da57f1c39f5db9c47bdaa94f74727ff

Test Status:
============
There is a testcase provided in the Bugzilla.  A 'cat /proc/interrupts' should
show the device drivers has two interrupt entries for each port.  Run I/O
tests.  Then 'lspci -vv' should display the correct pci capabilities for the
installed adapter and show the adapter is using MSI-X interrupts opposed to MSO
or LSI interrupts.

===============================================================
Ameet Paranjape 978-392-3903 ext 23903
IBM on-site partner

Proposed Patch:
===============

diff --git a/arch/powerpc/kernel/msi-rtas.c b/arch/powerpc/kernel/msi-rtas.c
index e5ba47e..05e7b02 100644
--- a/arch/powerpc/kernel/msi-rtas.c
+++ b/arch/powerpc/kernel/msi-rtas.c
@@ -152,7 +152,11 @@ static int check_req(struct pci_dev *pdev, int nvec, char *prop_name)
 
 	if (*req_msi < nvec) {
 		pr_debug("rtas_msi: %s requests < %d MSIs\n", prop_name, nvec);
-		return -ENOSPC;
+
+		if (*req_msi == 0) /* Be paranoid */
+			return -ENOSPC;
+
+		return *req_msi;
 	}
 
 	return 0;