[PATCH] usertools: add check for IOMMU support in dpdk-devbind

[Fidaullah Noonari]

I agree with your suggestion. I would add new flag for noiommu and
submit v2 for the patch.


On Tue, Mar 8, 2022 at 5:57 PM Bruce Richardson
<bruce.richardson at intel.com> wrote:
>
> On Tue, Mar 08, 2022 at 05:49:01PM +0500, Fidaullah Noonari wrote:
> > binding with vfio driver, when IOMMU is disabled, causes program to crash.
> > this patch checks for IOMMU support, if it is disabled, changes vfio
> > into unsafe noiommu mode and prints a warning message.
> >
> > Signed-off-by: Fidaullah Noonari <fidaullah.noonari at gmai.com>
> > ---
> >  usertools/dpdk-devbind.py | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/usertools/dpdk-devbind.py b/usertools/dpdk-devbind.py
> > index ace4627218..f42eead0c4 100755
> > --- a/usertools/dpdk-devbind.py
> > +++ b/usertools/dpdk-devbind.py
> > @@ -466,6 +466,26 @@ def unbind_all(dev_list, force=False):
> >          unbind_one(d, force)
> >
> >
> > +def check_iommu():
> > +    """Check if IOMMU is enabled on system"""
> > +    if len(os.listdir("/sys/class/iommu")) != 0:
> > +        return True
> > +    print("Warning: IOMMU support disabled")
> > +    return False
> > +
> > +
> > +def enable_noiommu_mode():
> > +    """Enables the noiommu mode for vfio drivers"""
> > +    filename = "/sys/module/vfio/parameters/enable_unsafe_noiommu_mode"
> > +    try:
> > +        f = open(filename, "w")
> > +    except:
> > +        sys.exit("Error: unable to enable noiommu mode, could not open '%s'" % filename)
> > +    f.write("1")
> > +    f.close()
> > +    print("Warning: enabling unsafe no IOMMU mode for vfio drivers")
> > +
> > +
> >  def bind_all(dev_list, driver, force=False):
> >      """Bind method, takes a list of device locations"""
> >      global devices
> > @@ -492,6 +512,11 @@ def bind_all(dev_list, driver, force=False):
> >      except ValueError as ex:
> >          sys.exit(ex)
> >
> > +    # check for IOMMU support
> > +    if not check_iommu():
> > +        if driver == "vfio-pci":
> > +            enable_noiommu_mode()
> > +
> >      for d in dev_list:
> >          bind_one(d, driver, force)
> >
> I like the idea of doing this from the script, but I would rather it not
> happen by default, since no-iommu reduces the security of the system. In
> the normal case, I think it would be best if the script printed an error
> message asking the user to enable iommu. We can also then add a flag to
> allow the user to explicitly ask for no-iommu mode and take the risk.
>
> /Bruce