From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: [RFC PATCH v2 3/3] vfio-pci: Allow to mmap MSI-X table if EEH is supported Date: Mon, 04 Jan 2016 14:07:35 -0700 Message-ID: <1451941655.6585.8.camel@redhat.com> References: <1451551844-11732-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1451551844-11732-4-git-send-email-xyjxie@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE 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 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 Return-path: In-Reply-To: <1451551844-11732-4-git-send-email-xyjxie@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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. >=20 > 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. >=20 > 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. >=20 > So this patch adds a Kconfig option, VFIO_PCI_MMAP_MSIX, > to support for mmapping MSI-X table. >=20 > Signed-off-by: Yongji Xie > --- > =C2=A0drivers/vfio/pci/Kconfig=C2=A0=C2=A0=C2=A0=C2=A0|=C2=A0=C2=A0=C2= =A0=C2=A04 ++++ > =C2=A0drivers/vfio/pci/vfio_pci.c |=C2=A0=C2=A0=C2=A0=C2=A06 ++++-- > =C2=A02 files changed, 8 insertions(+), 2 deletions(-) >=20 > 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 > =C2=A0 depends on VFIO_PCI > =C2=A0 def_bool y if !S390 > =C2=A0 > +config VFIO_PCI_MMAP_MSIX > + depends on VFIO_PCI_MMAP > + def_bool y if EEH Does CONFIG_EEH necessarily mean the EEH is enabled? =C2=A0Could the sy= stem not support EEH or could EEH be disabled via kernel commandline options? > + > =C2=A0config VFIO_PCI_INTX > =C2=A0 depends on VFIO_PCI > =C2=A0 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, > =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0IORESOURCE_MEM && (info.size >=3D > PAGE_SIZE || > =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0pci_resource_page_aligned)) { > =C2=A0 info.flags |=3D > VFIO_REGION_INFO_FLAG_MMAP; > - if (info.index =3D=3D vdev->msix_bar) { > + if > (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP_MSIX) && > + =C2=A0=C2=A0=C2=A0=C2=A0info.index =3D=3D vdev->msix_bar) { > =C2=A0 ret =3D > msix_sparse_mmap_cap(vdev, &caps); > =C2=A0 if (ret) > =C2=A0 return ret; > @@ -967,7 +968,8 @@ static int vfio_pci_mmap(void *device_data, > struct vm_area_struct *vma) > =C2=A0 if (phys_len < PAGE_SIZE || req_start + req_len > phys_len) > =C2=A0 return -EINVAL; > =C2=A0 > - if (index =3D=3D vdev->msix_bar) { > + if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP_MSIX) && > + =C2=A0=C2=A0=C2=A0=C2=A0index =3D=3D vdev->msix_bar) { > =C2=A0 /* > =C2=A0 =C2=A0* Disallow mmaps overlapping the MSI-X table; users > don't > =C2=A0 =C2=A0* get to touch this directly.=C2=A0=C2=A0We could find > somewhere