From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com ([134.134.136.20]:30793 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190AbbJGUVi (ORCPT ); Wed, 7 Oct 2015 16:21:38 -0400 Date: Wed, 7 Oct 2015 15:21:36 -0500 From: Ben Shelton To: Bjorn Helgaas Cc: bhelgaas@google.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PCI: IOV: reread SRIOV_NUM_VF after enabling ARI Message-ID: <20151007202136.GA19836@bhshelto-vm> References: <1442008500-3570-1-git-send-email-benjamin.h.shelton@intel.com> <20151007192940.GE27633@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20151007192940.GE27633@localhost> Sender: linux-pci-owner@vger.kernel.org List-ID: Hi Bjorn, On Wed, Oct 07, 2015 at 02:29:40PM -0500, Bjorn Helgaas wrote: > Hi Ben, > > On Fri, Sep 11, 2015 at 04:55:00PM -0500, Ben Shelton wrote: > > For some SR-IOV devices, the number of available virtual functions > > increases after enabling ARI. Currently, SRIOV_NUM_VF is read and saved > > off before the ARI control bit is enabled. This causes an issue when VFs > > are enabled. > > > > At device init, SRIOV_INITIAL_VF and SRIOV_NUM_VF are specified to contain > > the number of available VFs for the device. sriov_enable() does a sanity > > check that PCI_SRIOV_INITIAL_VF is not greater than iov->total_VFs, the > > saved-off value of SRIOV_NUM_VF. Since the value of both SRIOV_INITIAL_VF > > and SRIOV_NUM_VF has increased after enabling the ARI bit, the check fails, > > and the VFs cannot be enabled. > > > > To fix the issue, after ARI is enabled for a device, reread SRIOV_NUM_VF. > > > > Signed-off-by: Ben Shelton > > --- > > drivers/pci/iov.c | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c > > index ee0ebff..88b1959 100644 > > --- a/drivers/pci/iov.c > > +++ b/drivers/pci/iov.c > > @@ -388,6 +388,7 @@ static int sriov_init(struct pci_dev *dev, int pos) > > struct pci_sriov *iov; > > struct resource *res; > > struct pci_dev *pdev; > > + bool total_needs_reread = false; > > > > if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_END && > > pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT) > > @@ -409,12 +410,18 @@ static int sriov_init(struct pci_dev *dev, int pos) > > goto found; > > > > pdev = NULL; > > - if (pci_ari_enabled(dev->bus)) > > + if (pci_ari_enabled(dev->bus)) { > > ctrl |= PCI_SRIOV_CTRL_ARI; > > + total_needs_reread = true; > > + } > > > > found: > > pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, ctrl); > > pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, 0); > > + > > + if (total_needs_reread) > > + pci_read_config_word(dev, pos + PCI_SRIOV_TOTAL_VF, &total); > > Can we just *move* the PCI_SRIOV_TOTAL_VF read from its original > location and do it unconditionally here? I don't think we use "total" > for anything in the interim, and it'd be nice if we could do this > without the "total_needs_reread" flag. The only thing we do with 'total' is return early if it's read as 0 (i.e. for a device that does not support any VFs). If we just move the read to here, a PCI device with no VFs would have its PCI_SRIOV_CTRL config word written before PCI_SRIOV_TOTAL_VF is read as 0 and sriov_init() returns. The reread preserves the original behavior. If the change in behavior is OK, I'll make the change and submit a v2. Thanks, Ben > > > pci_read_config_word(dev, pos + PCI_SRIOV_VF_OFFSET, &offset); > > pci_read_config_word(dev, pos + PCI_SRIOV_VF_STRIDE, &stride); > > if (!offset || (total > 1 && !stride)) > > -- > > 1.9.5 > > > > -- > > 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/