Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754787AbaFLUkd (ORCPT ); Thu, 12 Jun 2014 16:40:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41583 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754109AbaFLUjJ (ORCPT ); Thu, 12 Jun 2014 16:39:09 -0400 From: Bandan Das To: Alex Williamson Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH] vfio/pci: Add extra test for extended capabilities References: <20140612164349.9739.53824.stgit@bling.home> <1402604942.3707.17.camel@ul30vt.home> Date: Thu, 12 Jun 2014 16:39:08 -0400 In-Reply-To: <1402604942.3707.17.camel@ul30vt.home> (Alex Williamson's message of "Thu, 12 Jun 2014 14:29:02 -0600") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alex Williamson writes: > On Thu, 2014-06-12 at 16:12 -0400, Bandan Das wrote: >> Alex Williamson writes: >> >> > If the PCI core set cfg_size isn't large enough for extended >> > capabilities, then they're not there. Extended config space may be >> > inaccessible due to a PCI bridge, in which case cfg_size may be cut >> > short. >> >> Just curious, is this part of the spec or just a convention ? I mean >> could there be devices with quirks ? > > The PCIe bridge spec indicates that PCIe-to-PCI bridges should handle > extended config accesses as an unsupported request. But as in 78916b00, > we've seen that's not always the case. This just makes us trust > PCI-core before the capabilities we find on the device. The current > quirk in the referenced commit is for a relatively uncommon topology, > but never rule out that we couldn't have a device quirked to avoid > touching extended config space too. Thanks, Ok, Understood, Thanks! > Alex > >> > Signed-off-by: Alex Williamson >> > --- >> > drivers/vfio/pci/vfio_pci_config.c | 13 +++++++++---- >> > 1 file changed, 9 insertions(+), 4 deletions(-) >> > >> > diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c >> > index 83cd157..4a62a37 100644 >> > --- a/drivers/vfio/pci/vfio_pci_config.c >> > +++ b/drivers/vfio/pci/vfio_pci_config.c >> > @@ -1027,8 +1027,11 @@ static int vfio_cap_len(struct vfio_pci_device *vdev, u8 cap, u8 pos) >> > >> > if (PCI_X_CMD_VERSION(word)) { >> > /* Test for extended capabilities */ >> > - pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword); >> > - vdev->extended_caps = (dword != 0); >> > + if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) { >> > + pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, >> > + &dword); >> > + vdev->extended_caps = (dword != 0); >> > + } >> > return PCI_CAP_PCIX_SIZEOF_V2; >> > } else >> > return PCI_CAP_PCIX_SIZEOF_V0; >> > @@ -1041,8 +1044,10 @@ static int vfio_cap_len(struct vfio_pci_device *vdev, u8 cap, u8 pos) >> > return byte; >> > case PCI_CAP_ID_EXP: >> > /* Test for extended capabilities */ >> > - pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword); >> > - vdev->extended_caps = (dword != 0); >> > + if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) { >> > + pci_read_config_dword(pdev, PCI_CFG_SPACE_SIZE, &dword); >> > + vdev->extended_caps = (dword != 0); >> > + } >> > >> > /* length based on version */ >> > if ((pcie_caps_reg(pdev) & PCI_EXP_FLAGS_VERS) == 1) >> > >> > -- >> > To unsubscribe from this list: send the line "unsubscribe kvm" in >> > the body of a message to majordomo@vger.kernel.org >> > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/