Re: [Qemu-devel] [PATCHv3 1/7] vfio: Start improving VFIO/EEH interface

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Mar 08, 2016 at 11:33:45AM -0700, Alex Williamson wrote:
> On Tue,  8 Mar 2016 13:10:23 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > At present the code handling IBM's Enhanced Error Handling (EEH) interface
> > on VFIO devices operates by bypassing the usual VFIO logic with
> > vfio_container_ioctl().  That's a poorly designed interface with unclear
> > semantics about exactly what can be operated on.
> > 
> > In particular it operates on a single vfio container internally (hence the
> > name), but takes an address space and group id, from which it deduces the
> > container in a rather roundabout way.  groupids are something that code
> > outside vfio shouldn't even be aware of.
> > 
> > This patch creates new interfaces for EEH operations.  Internally we
> > have vfio_eeh_container_op() which takes a VFIOContainer object
> > directly.  For external use we have vfio_eeh_as_ok() which determines
> > if an AddressSpace is usable for EEH (at present this means it has a
> > single container with exactly one group attached), and vfio_eeh_as_op()
> > which will perform an operation on an AddressSpace in the unambiguous case,
> > and otherwise returns an error.
> > 
> > This interface still isn't great, but it's enough of an improvement to
> > allow a number of cleanups in other places.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > ---
> 
> I'll let you push this through your tree:
> 
> Acked-by: Alex Williamson <alex.williamson@redhat.com>

Thanks.  Any guess at when your vGPU series will be pushed?  Mine will
conflict until that is merged upstream.

> 
> >  hw/vfio/common.c       | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/hw/vfio/vfio.h |  2 ++
> >  2 files changed, 97 insertions(+)
> > 
> > diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> > index 96ccb79..0636bb1 100644
> > --- a/hw/vfio/common.c
> > +++ b/hw/vfio/common.c
> > @@ -1137,3 +1137,98 @@ int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
> >  
> >      return vfio_container_do_ioctl(as, groupid, req, param);
> >  }
> > +
> > +/*
> > + * Interfaces for IBM EEH (Enhanced Error Handling)
> > + */
> > +static bool vfio_eeh_container_ok(VFIOContainer *container)
> > +{
> > +    /*
> > +     * As of 2016-03-04 (linux-4.5) the host kernel EEH/VFIO
> > +     * implementation is broken if there are multiple groups in a
> > +     * container.  The hardware works in units of Partitionable
> > +     * Endpoints (== IOMMU groups) and the EEH operations naively
> > +     * iterate across all groups in the container, without any logic
> > +     * to make sure the groups have their state synchronized.  For
> > +     * certain operations (ENABLE) that might be ok, until an error
> > +     * occurs, but for others (GET_STATE) it's clearly broken.
> > +     */
> > +
> > +    /*
> > +     * XXX Once fixed kernels exist, test for them here
> > +     */
> > +
> > +    if (QLIST_EMPTY(&container->group_list)) {
> > +        return false;
> > +    }
> > +
> > +    if (QLIST_NEXT(QLIST_FIRST(&container->group_list), container_next)) {
> > +        return false;
> > +    }
> > +
> > +    return true;
> > +}
> > +
> > +static int vfio_eeh_container_op(VFIOContainer *container, uint32_t op)
> > +{
> > +    struct vfio_eeh_pe_op pe_op = {
> > +        .argsz = sizeof(pe_op),
> > +        .op = op,
> > +    };
> > +    int ret;
> > +
> > +    if (!vfio_eeh_container_ok(container)) {
> > +        error_report("vfio/eeh: EEH_PE_OP 0x%x: "
> > +                     "kernel requires a container with exactly one group", op);
> > +        return -EPERM;
> > +    }
> > +
> > +    ret = ioctl(container->fd, VFIO_EEH_PE_OP, &pe_op);
> > +    if (ret < 0) {
> > +        error_report("vfio/eeh: EEH_PE_OP 0x%x failed: %m", op);
> > +        return -errno;
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> > +static VFIOContainer *vfio_eeh_as_container(AddressSpace *as)
> > +{
> > +    VFIOAddressSpace *space = vfio_get_address_space(as);
> > +    VFIOContainer *container = NULL;
> > +
> > +    if (QLIST_EMPTY(&space->containers)) {
> > +        /* No containers to act on */
> > +        goto out;
> > +    }
> > +
> > +    container = QLIST_FIRST(&space->containers);
> > +
> > +    if (QLIST_NEXT(container, next)) {
> > +        /* We don't yet have logic to synchronize EEH state across
> > +         * multiple containers */
> > +        container = NULL;
> > +        goto out;
> > +    }
> > +
> > +out:
> > +    vfio_put_address_space(space);
> > +    return container;
> > +}
> > +
> > +bool vfio_eeh_as_ok(AddressSpace *as)
> > +{
> > +    VFIOContainer *container = vfio_eeh_as_container(as);
> > +
> > +    return (container != NULL) && vfio_eeh_container_ok(container);
> > +}
> > +
> > +int vfio_eeh_as_op(AddressSpace *as, uint32_t op)
> > +{
> > +    VFIOContainer *container = vfio_eeh_as_container(as);
> > +
> > +    if (!container) {
> > +        return -ENODEV;
> > +    }
> > +    return vfio_eeh_container_op(container, op);
> > +}
> > diff --git a/include/hw/vfio/vfio.h b/include/hw/vfio/vfio.h
> > index 0b26cd8..fd3933b 100644
> > --- a/include/hw/vfio/vfio.h
> > +++ b/include/hw/vfio/vfio.h
> > @@ -5,5 +5,7 @@
> >  
> >  extern int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
> >                                  int req, void *param);
> > +bool vfio_eeh_as_ok(AddressSpace *as);
> > +int vfio_eeh_as_op(AddressSpace *as, uint32_t op);
> >  
> >  #endif
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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