Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756319Ab3JGUcH (ORCPT ); Mon, 7 Oct 2013 16:32:07 -0400 Received: from mga14.intel.com ([143.182.124.37]:2898 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755681Ab3JGUcC (ORCPT ); Mon, 7 Oct 2013 16:32:02 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,1051,1371106800"; d="scan'208";a="406823011" Date: Mon, 7 Oct 2013 13:31:18 -0700 From: Jon Mason To: Alexander Gordeev Cc: linux-kernel@vger.kernel.org, Bjorn Helgaas , Ralf Baechle , Michael Ellerman , Benjamin Herrenschmidt , Martin Schwidefsky , Ingo Molnar , Tejun Heo , Dan Williams , Andy King , Matt Porter , stable@vger.kernel.org, linux-pci@vger.kernel.org, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux390@de.ibm.com, linux-s390@vger.kernel.org, x86@kernel.org, linux-ide@vger.kernel.org, iss_storagedev@hp.com, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, netdev@vger.kernel.org, e1000-devel@lists.sourceforge.net, linux-driver@qlogic.com, Solarflare linux maintainers , "VMware, Inc." , linux-scsi@vger.kernel.org Subject: Re: [PATCH RFC 54/77] ntb: Ensure number of MSIs on SNB is enough for the link interrupt Message-ID: <20131007203114.GD24536@jonmason-lab> References: <5d9c5b2d3bbc444ff32bddeece7a239d046bd79c.1380703263.git.agordeev@redhat.com> <20131003004805.GL6768@jonmason-lab> <20131005214303.GA21589@dhcp-26-207.brq.redhat.com> <20131007165056.GA24536@jonmason-lab> <20131007183845.GA1834@dhcp-26-207.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131007183845.GA1834@dhcp-26-207.brq.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3314 Lines: 96 On Mon, Oct 07, 2013 at 08:38:45PM +0200, Alexander Gordeev wrote: > On Mon, Oct 07, 2013 at 09:50:57AM -0700, Jon Mason wrote: > > On Sat, Oct 05, 2013 at 11:43:04PM +0200, Alexander Gordeev wrote: > > > On Wed, Oct 02, 2013 at 05:48:05PM -0700, Jon Mason wrote: > > > > On Wed, Oct 02, 2013 at 12:49:10PM +0200, Alexander Gordeev wrote: > > > > > Signed-off-by: Alexander Gordeev > > > > > --- > > > > > drivers/ntb/ntb_hw.c | 2 +- > > > > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > > > > > > > diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c > > > > > index de2062c..eccd5e5 100644 > > > > > --- a/drivers/ntb/ntb_hw.c > > > > > +++ b/drivers/ntb/ntb_hw.c > > > > > @@ -1066,7 +1066,7 @@ static int ntb_setup_msix(struct ntb_device *ndev) > > > > > /* On SNB, the link interrupt is always tied to 4th vector. If > > > > > * we can't get all 4, then we can't use MSI-X. > > > > > */ > > > > > - if (ndev->hw_type != BWD_HW) { > > > > > + if ((rc < SNB_MSIX_CNT) && (ndev->hw_type != BWD_HW)) { > > > > > > > > Nack, this check is unnecessary. > > > > > > If SNB can do more than SNB_MSIX_CNT MSI-Xs then this check is needed > > > to enable less than maximum MSI-Xs in case the maximum was not allocated. > > > Otherwise SNB will fallback to single MSI instead of multiple MSI-Xs. > > > > Per the comment in the code snippet above, "If we can't get all 4, > > then we can't use MSI-X". There is already a check to see if more > > than 4 were acquired. So it's not possible to hit this. Even if it > > was, don't use SNB_MSIX_CNT here (limits.msix_cnt is the preferred > > variable). Also, the "()" are unnecessary. > > The changelog is definitely bogus. I meant here an improvement to the > existing scheme, not a conversion to the new one: > > msix_entries = msix_table_size(val); > > Getting i.e. 16 vectors here. > > if (msix_entries > ndev->limits.msix_cnt) { On SNB HW, limits.msix_cnt is set to SNB_MSIX_CNT (4) http://lxr.free-electrons.com/source/drivers/ntb/ntb_hw.c#L558 > rc = -EINVAL; > goto err; > } > > Upper limit check i.e. succeeds. > > [...] > > rc = pci_enable_msix(pdev, ndev->msix_entries, msix_entries); > > pci_enable_msix() does not success and returns i.e. 8 here, should retry. Per the above, since our upper bound is 4. We will either have this return 0 for all 4 or a number between 1 and 3 (or an error, but that's not relevant to this discussion). > if (rc < 0) > goto err1; > if (rc > 0) { > /* On SNB, the link interrupt is always tied to 4th vector. If > * we can't get all 4, then we can't use MSI-X. > */ > if (ndev->hw_type != BWD_HW) { > > On SNB bail out here, although could have continue with 8 vectors. > Can only use SNB_MSIX_CNT here, since limits.msix_cnt is the upper limit. Since we can guarantee that rc is between 1 and 3 at this point (on SNB HW), we should error out. Thanks, Jon > > rc = -EIO; > goto err1; > } > > [...] > } > > -- > Regards, > Alexander Gordeev > agordeev@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/