From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by ozlabs.org (Postfix) with ESMTP id 00C062C019C for ; Tue, 8 Oct 2013 05:37:20 +1100 (EST) Date: Mon, 7 Oct 2013 20:38:45 +0200 From: Alexander Gordeev To: Jon Mason Subject: Re: [PATCH RFC 54/77] ntb: Ensure number of MSIs on SNB is enough for the link interrupt Message-ID: <20131007183845.GA1834@dhcp-26-207.brq.redhat.com> References: <5d9c5b2d3bbc444ff32bddeece7a239d046bd79c.1380703263.git.agordeev@redhat.com> <20131003004805.GL6768@jonmason-lab> <20131005214303.GA21589@dhcp-26-207.brq.redhat.com> <20131007165056.GA24536@jonmason-lab> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20131007165056.GA24536@jonmason-lab> Cc: linux-mips@linux-mips.org, "VMware, Inc." , linux-nvme@lists.infradead.org, linux-ide@vger.kernel.org, stable@vger.kernel.org, linux-s390@vger.kernel.org, Andy King , linux-scsi@vger.kernel.org, linux-rdma@vger.kernel.org, x86@kernel.org, Ingo Molnar , linux-pci@vger.kernel.org, iss_storagedev@hp.com, linux-driver@qlogic.com, Tejun Heo , Bjorn Helgaas , Dan Williams , Solarflare linux maintainers , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Ralf Baechle , e1000-devel@lists.sourceforge.net, Martin Schwidefsky , linux390@de.ibm.com, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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) { 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. 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. rc = -EIO; goto err1; } [...] } -- Regards, Alexander Gordeev agordeev@redhat.com