From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 449141A117B for ; Tue, 5 Jan 2016 08:07:38 +1100 (AEDT) Message-ID: <1451941655.6585.8.camel@redhat.com> Subject: Re: [RFC PATCH v2 3/3] vfio-pci: Allow to mmap MSI-X table if EEH is supported From: Alex Williamson To: Yongji Xie , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org Cc: 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 Date: Mon, 04 Jan 2016 14:07:35 -0700 In-Reply-To: <1451551844-11732-4-git-send-email-xyjxie@linux.vnet.ibm.com> References: <1451551844-11732-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1451551844-11732-4-git-send-email-xyjxie@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2015-12-31 at 16:50 +0800, Yongji Xie wrote: > Current vfio-pci implementation disallows to mmap MSI-X > table in case that user get to touch this directly. > > However, EEH mechanism can ensure that a given pci device > can only shoot the MSIs assigned for its PE. So we think > it's safe to expose the MSI-X table to userspace because > the exposed MSI-X table can't be used to do harm to other > memory space. > > And with MSI-X table mmapped, some performance issues which > are caused when PCI adapters have critical registers in the > same page as the MSI-X table also can be resolved. > > So this patch adds a Kconfig option, VFIO_PCI_MMAP_MSIX, > to support for mmapping MSI-X table. > > Signed-off-by: Yongji Xie > --- >  drivers/vfio/pci/Kconfig    |    4 ++++ >  drivers/vfio/pci/vfio_pci.c |    6 ++++-- >  2 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig > index 02912f1..67b0a2c 100644 > --- a/drivers/vfio/pci/Kconfig > +++ b/drivers/vfio/pci/Kconfig > @@ -23,6 +23,10 @@ config VFIO_PCI_MMAP >   depends on VFIO_PCI >   def_bool y if !S390 >   > +config VFIO_PCI_MMAP_MSIX > + depends on VFIO_PCI_MMAP > + def_bool y if EEH Does CONFIG_EEH necessarily mean the EEH is enabled?  Could the system not support EEH or could EEH be disabled via kernel commandline options? > + >  config VFIO_PCI_INTX >   depends on VFIO_PCI >   def_bool y if !S390 > diff --git a/drivers/vfio/pci/vfio_pci.c > b/drivers/vfio/pci/vfio_pci.c > index 09b3805..d536985 100644 > --- a/drivers/vfio/pci/vfio_pci.c > +++ b/drivers/vfio/pci/vfio_pci.c > @@ -555,7 +555,8 @@ static long vfio_pci_ioctl(void *device_data, >       IORESOURCE_MEM && (info.size >= > PAGE_SIZE || >       pci_resource_page_aligned)) { >   info.flags |= > VFIO_REGION_INFO_FLAG_MMAP; > - if (info.index == vdev->msix_bar) { > + if > (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP_MSIX) && > +     info.index == vdev->msix_bar) { >   ret = > msix_sparse_mmap_cap(vdev, &caps); >   if (ret) >   return ret; > @@ -967,7 +968,8 @@ static int vfio_pci_mmap(void *device_data, > struct vm_area_struct *vma) >   if (phys_len < PAGE_SIZE || req_start + req_len > phys_len) >   return -EINVAL; >   > - if (index == vdev->msix_bar) { > + if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP_MSIX) && > +     index == vdev->msix_bar) { >   /* >    * Disallow mmaps overlapping the MSI-X table; users > don't >    * get to touch this directly.  We could find > somewhere