Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755693AbcJTVOz (ORCPT ); Thu, 20 Oct 2016 17:14:55 -0400 Received: from hqemgate14.nvidia.com ([216.228.121.143]:10671 "EHLO hqemgate14.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751741AbcJTVOx (ORCPT ); Thu, 20 Oct 2016 17:14:53 -0400 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Thu, 20 Oct 2016 14:07:39 -0700 Subject: Re: [PATCH v9 10/12] vfio: Add function to get device_api string from vfio_device_info.flags To: Alex Williamson References: <1476739332-4911-1-git-send-email-kwankhede@nvidia.com> <1476739332-4911-11-git-send-email-kwankhede@nvidia.com> <20161020133403.08828f47@t450s.home> <20161020150501.39f28c7e@t450s.home> CC: , , , , , , , , X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: <6687c068-33f0-c437-3106-bbd1d22f4d81@nvidia.com> Date: Fri, 21 Oct 2016 02:44:37 +0530 MIME-Version: 1.0 In-Reply-To: <20161020150501.39f28c7e@t450s.home> X-Originating-IP: [10.24.71.144] X-ClientProxiedBy: BGMAIL102.nvidia.com (10.25.59.11) To bgmail102.nvidia.com (10.25.59.11) Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3880 Lines: 109 On 10/21/2016 2:35 AM, Alex Williamson wrote: > On Fri, 21 Oct 2016 01:59:55 +0530 > Kirti Wankhede wrote: > >> On 10/21/2016 1:04 AM, Alex Williamson wrote: >>> On Tue, 18 Oct 2016 02:52:10 +0530 >>> Kirti Wankhede wrote: >>> >>>> Function vfio_device_api_string() returns string based on flag set in >>>> vfio_device_info's flag. This should be used by vendor driver to get string >>>> based on flag for device_api attribute. >>>> >>>> Signed-off-by: Kirti Wankhede >>>> Signed-off-by: Neo Jia >>>> Change-Id: I42d29f475f02a7132ce13297fbf2b48f1da10995 >>>> --- >>>> drivers/vfio/vfio.c | 15 +++++++++++++++ >>>> include/linux/vfio.h | 2 ++ >>>> 2 files changed, 17 insertions(+) >>>> >>>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c >>>> index 10ef1c5fa762..aec470454a13 100644 >>>> --- a/drivers/vfio/vfio.c >>>> +++ b/drivers/vfio/vfio.c >>>> @@ -1917,6 +1917,21 @@ int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr, int num_irqs, >>>> } >>>> EXPORT_SYMBOL(vfio_set_irqs_validate_and_prepare); >>>> >>>> +const char *vfio_device_api_string(u32 flags) >>>> +{ >>>> + if (flags & VFIO_DEVICE_FLAGS_PCI) >>>> + return "vfio-pci"; >>>> + >>>> + if (flags & VFIO_DEVICE_FLAGS_PLATFORM) >>>> + return "vfio-platform"; >>>> + >>>> + if (flags & VFIO_DEVICE_FLAGS_AMBA) >>>> + return "vfio-amba"; >>>> + >>>> + return ""; >>>> +} >>>> +EXPORT_SYMBOL(vfio_device_api_string); >>>> + >>>> /* >>>> * Pin a set of guest PFNs and return their associated host PFNs for local >>>> * domain only. >>>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h >>>> index 31d059f1649b..fca2bf23c4f1 100644 >>>> --- a/include/linux/vfio.h >>>> +++ b/include/linux/vfio.h >>>> @@ -116,6 +116,8 @@ extern int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr, >>>> int num_irqs, int max_irq_type, >>>> size_t *data_size); >>>> >>>> +extern const char *vfio_device_api_string(u32 flags); >>>> + >>>> struct pci_dev; >>>> #ifdef CONFIG_EEH >>>> extern void vfio_spapr_pci_eeh_open(struct pci_dev *pdev); >>> >>> Couldn't this simply be a #define in the uapi header? >>> >>> #define VFIO_DEVICE_PCI_API_STRING "vfio-pci" >>> >>> I don't really see why we need a lookup function. >>> >> >> String is tightly coupled with the FLAG, right? >> Instead user need to take care of making sure to return proper string, >> and don't mis-match the string, I think having function is easier. > > That's exactly why I proposed putting the #define string in the uapi, > by that I mean the vfio uapi header. That keeps the tight coupling to > the flag, they're both defined in the same place, plus it gives > userspace a reference so they're not just inventing a string to compare > against. IOW, the vendor driver simply does an sprintf of > VFIO_DEVICE_PCI_API_STRING and userspace (ie. libvirt) can do a strcmp > with VFIO_DEVICE_PCI_API_STRING from the same header and everybody > arrives at the same result. > >> Vendor driver should decide the type of device they want to expose and >> set the flag, using this function vendor driver would return string >> which is based on flag they set. > > Being a function adds no intrinsic value and being in a uapi header does > add value to userspace. Thanks, > Ok. The strings should be in uapi, but having function (like below) to return proper string based on flag would be good to have for vendor driver. +const char *vfio_device_api_string(u32 flags) +{ + if (flags & VFIO_DEVICE_FLAGS_PCI) + return VFIO_DEVICE_API_PCI_STRING; + + if (flags & VFIO_DEVICE_FLAGS_PLATFORM) + return VFIO_DEVICE_API_PLATFORM_STRING; + + if (flags & VFIO_DEVICE_FLAGS_AMBA) + return VFIO_DEVICE_API_AMBA_STRING; + + return ""; +} +EXPORT_SYMBOL(vfio_device_api_string); Kirti