From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) (using TLSv1 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3E6071A058F for ; Thu, 29 May 2014 09:38:51 +1000 (EST) Message-ID: <53867386.9060403@suse.de> Date: Thu, 29 May 2014 01:38:46 +0200 From: Alexander Graf MIME-Version: 1.0 To: Gavin Shan Subject: Re: [PATCH v7 3/3] drivers/vfio: EEH support for VFIO PCI device 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> <1401293853.2412.36.camel@ul30vt.home> <538665DA.8090000@suse.de> <20140528233753.GA8150@shangw> In-Reply-To: <20140528233753.GA8150@shangw> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: aik@ozlabs.ru, kvm-ppc@vger.kernel.org, Alex Williamson , 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 29.05.14 01:37, Gavin Shan wrote: > On Thu, May 29, 2014 at 12:40:26AM +0200, Alexander Graf wrote: >> On 28.05.14 18:17, Alex Williamson wrote: >>> 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, >> Yup, that looks well to me as well :) >> > s/VFIO_EEH_PE_GET_MODE/VFIO_EEH_PE_GET_STATE. > > I'll include this in next revision. Thanks, Alex. Yup, no need for CMD anymore then either :) Alex