Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030720AbcCQMsr (ORCPT ); Thu, 17 Mar 2016 08:48:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46636 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752669AbcCQMso (ORCPT ); Thu, 17 Mar 2016 08:48:44 -0400 Date: Thu, 17 Mar 2016 06:48:42 -0600 From: Alex Williamson To: Yongji Xie Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, bhelgaas@google.com, corbet@lwn.net, aik@ozlabs.ru, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, warrier@linux.vnet.ibm.com, zhong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com Subject: Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add IOMMU_CAP_INTR_REMAP for IODA host bridge Message-ID: <20160317064842.764d8f22@ul30vt.home> In-Reply-To: <56EA9735.2010401@linux.vnet.ibm.com> References: <1457336918-3893-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1457336918-3893-8-git-send-email-xyjxie@linux.vnet.ibm.com> <20160316103207.6fffb9b5@t450s.home> <56EA9735.2010401@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 17 Mar 2016 12:48:44 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2630 Lines: 71 On Thu, 17 Mar 2016 19:38:29 +0800 Yongji Xie wrote: > On 2016/3/17 0:32, Alex Williamson wrote: > > On Mon, 7 Mar 2016 15:48:38 +0800 > > Yongji Xie wrote: > > > >> This patch adds IOMMU_CAP_INTR_REMAP for IODA host bridge so that > >> we can mmap MSI-X table in vfio driver. > >> > >> Signed-off-by: Yongji Xie > >> --- > >> arch/powerpc/platforms/powernv/pci-ioda.c | 17 +++++++++++++++++ > >> 1 file changed, 17 insertions(+) > >> > >> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c > >> index f90dc04..f01b9ab 100644 > >> --- a/arch/powerpc/platforms/powernv/pci-ioda.c > >> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c > >> @@ -1955,6 +1955,20 @@ static struct iommu_table_ops pnv_ioda2_iommu_ops = { > >> .free = pnv_ioda2_table_free, > >> }; > >> > >> +static bool pnv_ioda_iommu_capable(enum iommu_cap cap) > >> +{ > >> + switch (cap) { > >> + case IOMMU_CAP_INTR_REMAP: > >> + return true; > >> + default: > >> + return false; > >> + } > >> +} > >> + > >> +static struct iommu_ops pnv_ioda_iommu_ops = { > >> + .capable = pnv_ioda_iommu_capable, > >> +}; > >> + > >> static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb, > >> struct pnv_ioda_pe *pe, unsigned int base, > >> unsigned int segs) > >> @@ -3078,6 +3092,9 @@ static void pnv_pci_ioda_fixup(void) > >> > >> /* Link NPU IODA tables to their PCI devices. */ > >> pnv_npu_ioda_fixup(); > >> + > >> + /* Add IOMMU_CAP_INTR_REMAP */ > >> + bus_set_iommu(&pci_bus_type, &pnv_ioda_iommu_ops); > >> } > >> > >> /* > > > > Doesn't this set you up for a world of hurt? bus_set_iommu() calls > > iommu_bus_init() which sets up notifiers, which maybe you don't care > > about, but it also means that iommu_domain_alloc(&pci_bus_type) will > > segfault because you're not providing a domain_alloc callback here. > > It seems to be hard to add IOMMU_CAP_INTR_REMAP on > PPC64 platform. > > And can we add a new ioctl in vfio_iommu_driver to check > if interrupt remapping is supported so that we can use our > own way to determine that on PPC64 platform? I'd prefer not. At the vfio user API level, the question is whether the user can mmap over the msix table, testing a property/ioctl on the iommu driver seems like an odd way to discover that. We should be determining whether that's safe in the kernel and exporting that info on the vfio device itself, where it seems like we have various ways we could do this within the existing ioctls. Thanks, Alex