From patchwork Thu May 7 08:28:41 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 22259 Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n478V1AI020824 for ; Thu, 7 May 2009 08:31:02 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755089AbZEGIa4 (ORCPT ); Thu, 7 May 2009 04:30:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751815AbZEGIa4 (ORCPT ); Thu, 7 May 2009 04:30:56 -0400 Received: from mx2.redhat.com ([66.187.237.31]:39937 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751171AbZEGIay (ORCPT ); Thu, 7 May 2009 04:30:54 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n478Tm9W003790; Thu, 7 May 2009 04:29:48 -0400 Received: from ns3.rdu.redhat.com (ns3.rdu.redhat.com [10.11.255.199]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n478TlFO023653; Thu, 7 May 2009 04:29:47 -0400 Received: from redhat.com (dhcp-0-223.tlv.redhat.com [10.35.0.223]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id n478TeK5004775; Thu, 7 May 2009 04:29:41 -0400 Date: Thu, 7 May 2009 11:28:41 +0300 From: "Michael S. Tsirkin" To: jbarnes@virtuousgeek.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Matthew Wilcox Cc: virtualization@lists.linux-foundation.org, kvm@vger.kernel.org Subject: [PATCH] msi-x: let drivers retry when not enough vectors Message-ID: <20090507082841.GA31751@redhat.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) X-Scanned-By: MIMEDefang 2.58 on 172.16.27.26 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org pci_enable_msix currently returns -EINVAL if you ask for more vectors than supported by the device, which would typically cause fallback to regular interrupts. It's better to return the table size, making the driver retry MSI-X with less vectors. Signed-off-by: Michael S. Tsirkin Reviewed-by: Matthew Wilcox --- Hi Jesse, This came up when I was adding MSI-X support to virtio pci driver, which does not know the exact table size upfront. Could you consider this patch for 2.6.31 please? drivers/pci/msi.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index 6f2e629..f5bd1c9 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -687,8 +687,8 @@ int pci_msix_table_size(struct pci_dev *dev) * indicates the successful configuration of MSI-X capability structure * with new allocated MSI-X irqs. A return of < 0 indicates a failure. * Or a return of > 0 indicates that driver request is exceeding the number - * of irqs available. Driver should use the returned value to re-send - * its request. + * of irqs or MSI-X vectors available. Driver should use the returned value to + * re-send its request. **/ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec) { @@ -704,7 +704,7 @@ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec) nr_entries = pci_msix_table_size(dev); if (nvec > nr_entries) - return -EINVAL; + return nr_entries; /* Check for any invalid entries */ for (i = 0; i < nvec; i++) {