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.
