On Wed, Sep 30, 2015 at 10:28:07AM -0700, Stephen Hemminger wrote: > On Wed, 30 Sep 2015 13:37:22 +0300 > Vlad Zolotarov <vladz at cloudius-systems.com> wrote: > > > > > > > On 09/30/15 00:49, Michael S. Tsirkin wrote: > > > On Tue, Sep 29, 2015 at 02:46:16PM -0700, Stephen Hemminger wrote: > > >> On Tue, 29 Sep 2015 23:54:54 +0300 > > >> "Michael S. Tsirkin" <mst at redhat.com> wrote: > > >> > > >>> On Tue, Sep 29, 2015 at 07:41:09PM +0300, Vlad Zolotarov wrote: > > >>>> The security breach motivation u brought in "[RFC PATCH] uio: > > >>>> uio_pci_generic: Add support for MSI interrupts" thread seems a bit > > >>>> weak > > >>>> since one u let the userland access to the bar it may do any funny > > >>>> thing > > >>>> using the DMA engine of the device. This kind of stuff should be > > >>>> prevented > > >>>> using the iommu and if it's enabled then any funny tricks using > > >>>> MSI/MSI-X > > >>>> configuration will be prevented too. > > >>>> > > >>>> I'm about to send the patch to main Linux mailing list. Let's continue > > >>>> this > > >>>> discussion there. > > >>>> > > >>> Basically UIO shouldn't be used with devices capable of DMA. > > >>> Use VFIO for that (yes, this implies an emulated or PV IOMMU). > > > > If there is an IOMMU in the picture there shouldn't be any problem to > > use UIO with DMA capable devices. > > > > >>> I don't think this can change. > > >> Given there is no PV IOMMU and even if there was it would be too slow > > >> for DPDK > > >> use, I can't accept that. > > > QEMU does allow emulating an iommu. > > > > Amazon's EC2 xen HV doesn't. At least today. Therefore VFIO is not an > > option there. And again, it's a general issue not DPDK specific. > > Today one has to develop some proprietary modules (like igb_uio) to > > workaround the issue and this is lame. IMHO uio_pci_generic should > > be fixed to be able to properly work within any virtualized environment > > and not only with KVM. > > > > Also VMware (bigger problem) has no IOMMU emulation. > Other environments as well (Windriver, GCE) have noe IOMMU.
Because the use-case of userspace drivers is not important enough? Without an IOMMU, there's no way to have secure userspace drivers. -- MST
