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 lists.ozlabs.org (Postfix) with ESMTP id E0AB11A024F for ; Thu, 29 May 2014 02:17:47 +1000 (EST) Message-ID: <1401293853.2412.36.camel@ul30vt.home> Subject: Re: [PATCH v7 3/3] drivers/vfio: EEH support for VFIO PCI device From: Alex Williamson To: Alexander Graf Date: Wed, 28 May 2014 10:17:33 -0600 In-Reply-To: <5385CA86.3010700@suse.de> References: <1401180052-6060-1-git-send-email-gwshan@linux.vnet.ibm.com> <1401180052-6060-4-git-send-email-gwshan@linux.vnet.ibm.com> <1401214527.3289.611.camel@ul30vt.home> <5385166A.5060404@suse.de> <1401237575.3289.676.camel@ul30vt.home> <53853155.60809@suse.de> <1401238674.3289.679.camel@ul30vt.home> <5385CA86.3010700@suse.de> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: aik@ozlabs.ru, Gavin Shan , kvm-ppc@vger.kernel.org, qiudayu@linux.vnet.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 Wed, 2014-05-28 at 13:37 +0200, Alexander Graf wrote: > On 28.05.14 02:57, Alex Williamson wrote: > > On Wed, 2014-05-28 at 02:44 +0200, Alexander Graf wrote: > >> On 28.05.14 02:39, Alex Williamson wrote: > >>> On Wed, 2014-05-28 at 00:49 +0200, Alexander Graf wrote: > >>>> On 27.05.14 20:15, Alex Williamson wrote: > >>>>> On Tue, 2014-05-27 at 18:40 +1000, Gavin Shan wrote: > >>>>>> The patch adds new IOCTL commands for sPAPR VFIO container device > >>>>>> to support EEH functionality for PCI devices, which have been passed > >>>>>> through from host to somebody else via VFIO. > >>>>>> > >>>>>> Signed-off-by: Gavin Shan > >>>>>> --- > >>>>>> Documentation/vfio.txt | 92 ++++++++++++++++++++++++++++++++++++- > >>>>>> drivers/vfio/pci/Makefile | 1 + > >>>>>> drivers/vfio/pci/vfio_pci.c | 20 +++++--- > >>>>>> drivers/vfio/pci/vfio_pci_eeh.c | 46 +++++++++++++++++++ > >>>>>> drivers/vfio/pci/vfio_pci_private.h | 5 ++ > >>>>>> drivers/vfio/vfio_iommu_spapr_tce.c | 85 ++++++++++++++++++++++++++++++++++ > >>>>>> include/uapi/linux/vfio.h | 66 ++++++++++++++++++++++++++ > >>>>>> 7 files changed, 308 insertions(+), 7 deletions(-) > >>>>>> create mode 100644 drivers/vfio/pci/vfio_pci_eeh.c > >>>> [...] > >>>> > >>>>>> + > >>>>>> + return ret; > >>>>>> +} > >>>>>> + > >>>>>> static long tce_iommu_ioctl(void *iommu_data, > >>>>>> unsigned int cmd, unsigned long arg) > >>>>>> { > >>>>>> @@ -283,6 +363,11 @@ static long tce_iommu_ioctl(void *iommu_data, > >>>>>> tce_iommu_disable(container); > >>>>>> mutex_unlock(&container->lock); > >>>>>> return 0; > >>>>>> + case VFIO_EEH_PE_SET_OPTION: > >>>>>> + case VFIO_EEH_PE_GET_STATE: > >>>>>> + case VFIO_EEH_PE_RESET: > >>>>>> + case VFIO_EEH_PE_CONFIGURE: > >>>>>> + return tce_iommu_eeh_ioctl(iommu_data, cmd, arg); > >>>>> This is where it would have really made sense to have a single > >>>>> VFIO_EEH_OP ioctl with a data structure passed to indicate the sub-op. > >>>>> AlexG, are you really attached to splitting these out into separate > >>>>> ioctls? > >>>> I don't see the problem. We need to forward 4 ioctls to a separate piece > >>>> of code, so we forward 4 ioctls to a separate piece of code :). Putting > >>>> them into one ioctl just moves the switch() into another function. > >>> And uses an extra 3 ioctl numbers and gives us extra things to update if > >>> we ever need to add more ioctls, etc. ioctl numbers are an address > >>> space, how much address space do we really want to give to EEH? It's > >>> not a big difference, but I don't think it's completely even either. > >>> Thanks, > >> Yes, that's the point. I by far prefer to have you push back on anyone > >> who introduces useless ioctls rather than have a separate EEH number > >> space that people can just throw anything in they like ;). > > Well, I appreciate that, but having them as separate ioctls doesn't > > really prevent that either. Any one of these 4 could be set to take a > > sub-option to extend and contort the EEH interface. The only way to > > prevent that would be to avoid the argsz+flags hack that make the ioctl > > extendable. Thanks, > > Sure, that's what patch review is about. I'm really more concerned about > whose court the number space is in - you or Gavin. If we're talking > about top level ioctls you will care a lot more. > > But I'm not religious about this. You're the VFIO maintainer, so it's > your call. I just personally cringe when I see an ioctl that gets an > "opcode" and a "parameter" argument where the "parameter" argument is a > union with one struct for each opcode. Well, what would it look like... struct vfio_eeh_pe_op { __u32 argsz; __u32 flags; __u32 op; }; Couldn't every single one of these be a separate "op"? Are there any cases where we can't use the ioctl return value? VFIO_EEH_PE_DISABLE VFIO_EEH_PE_ENABLE VFIO_EEH_PE_UNFREEZE_IO VFIO_EEH_PE_UNFREEZE_DMA VFIO_EEH_PE_GET_MODE VFIO_EEH_PE_RESET_DEACTIVATE VFIO_EEH_PE_RESET_HOT VFIO_EEH_PE_RESET_FUNDAMENTAL VFIO_EEH_PE_CONFIGURE It doesn't look that bad to me, what am I missing? Thanks, Alex