Re: [Qemu-ppc] [Qemu-devel] [RFC PATCH 11/14] spapr_pci: Allow EEH on spapr-pci-host-bridge

[David Gibson]

On Wed, Sep 23, 2015 at 11:28:01AM -0600, Alex Williamson wrote:
> On Sat, 2015-09-19 at 17:18 +1000, David Gibson wrote:
> > The pseries machine type has two variants of the PCI Host Bridge device:
> > spapr-pci-host-bridge and spapr-pci-vfio-host-bridge.  Originally, only the
> > latter could support VFIO devices, but we've now extended the VFIO code so
> > that they both can.
> > 
> > However, it's still only spapr-pci-vfio-host-bridge which supports the PAPR
> > Enhanced Error Handling (EEH) interfaces.  The reason is that we don't yet
> > have a way to determine the correct VFIOGroup for EEH operations on the
> > "plain" host bridge.
> > 
> > Handling this in general is problematic due to some limitations in the
> > current code, and some bugs in the kernel EEH interfaces.  However, it's
> > easy enough to do for the unambiguous case: where there is only one VFIO
> > group used on the whole host bridge i.e. one Partitionable Endpoint (PE).
> > 
> > This re-implements spapr_phb_check_vfio_group() in terms of the host
> > bridge's Partitionable Endpoints, allowing EEH on any host bridge in the
> > unambiguous case.  This is enough to make spapr-pci-host-bridge support
> > EEH as well as spapr-pci-vfio-host-bridge, since the latter only supported
> > devices from one IOMMU group anyway (although it didn't properly
> > enforce that).
> > 
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> >  hw/ppc/spapr_pci.c          | 36 ++++++++++++++++++++++++++++++++++++
> >  hw/ppc/spapr_pci_vfio.c     | 18 ------------------
> >  include/hw/pci-host/spapr.h |  1 -
> >  3 files changed, 36 insertions(+), 19 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index 81ad3ae..5614b45 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -41,6 +41,8 @@
> >  #include "hw/ppc/spapr_drc.h"
> >  #include "sysemu/device_tree.h"
> >  
> > +#include "hw/vfio/vfio-common.h"
> > +
> >  /* Copied from the kernel arch/powerpc/platforms/pseries/msi.c */
> >  #define RTAS_QUERY_FN           0
> >  #define RTAS_CHANGE_FN          1
> > @@ -446,6 +448,40 @@ static sPAPRPHBGuestPE 
> > *spapr_phb_pe_by_device(sPAPRPHBState *phb,
> >      return pe;
> >  }
> >  
> > +static int spapr_phb_check_vfio_group(sPAPRPHBState *phb, VFIOGroup **gpp)
> > +{
> > +    sPAPRPHBGuestPE *pe;
> > +
> > +    if (QLIST_EMPTY(&phb->pe_list)) {
> > +        /* No EEH capable devices on this PHB */
> > +        return RTAS_OUT_PARAM_ERROR;
> > +    }
> > +
> > +    /* Limitations in both qemu and the kernel mean that, for now, EEH
> > +     * won't work if there are devices from more than one PE
> > +     * (i.e. IOMMU group) on the same PHB */
> > +    pe = QLIST_FIRST(&phb->pe_list);
> > +    if (QLIST_NEXT(pe, list)) {
> > +        error_report("spapr-pci-host-bridge: EEH attempted on PHB with 
> > multiple"
> > +                     " IOMMU groups");
> 
> Don't wrap lines with search-able strings

Noted.

> > +        return RTAS_OUT_HW_ERROR;
> > +    }
> > +
> > +    if (!object_dynamic_cast(OBJECT(phb), "spapr-pci-vfio-host-bridge")) {
> > +        sPAPRPHBVFIOState *svphb = SPAPR_PCI_VFIO_HOST_BRIDGE(phb);
> > +        /* FIXME: this is an abstraction violation */
> > +        if (pe->group->groupid != svphb->iommugroupid) {
> > +            error_report("spapr-pci-vfio-host-bridge: Bad IOMMU group");
> > +            return RTAS_OUT_HW_ERROR;
> > +        }
> > +    }
> > +
> > +    if (gpp) {
> > +        *gpp = pe->group;
> > +    }
> > +    return RTAS_OUT_SUCCESS;
> 
> 
> The structure of this function finally makes some sense once we get
> here.

Yeah, I started off with something more like what you suggested in
earlier comments, but I changed to this rather awkward structure to
avoid churning the callers as this moves towards its final form

> I'm still not sure whether RTAS error codes make sense though,
> but it's just a nit.

Well, (nearly) all the callers are in RTAS, and translating the error
codes there seems pretty ugly too.

> I'd still prefer the function was renamed, "check"
> indicates a verification, not a return.  The primary purpose of calling
> this function is to get a group, not simply to check the validity.

Yeah, it's a crap name.  How about spapr_phb_find_vfio_group().

Fwiw, I plan to make this function go away to as I rework things to
remove the one-group-per-PHB restriction.

> > +}
> > +
> >  static void rtas_ibm_set_eeh_option(PowerPCCPU *cpu,
> >                                      sPAPRMachineState *spapr,
> >                                      uint32_t token, uint32_t nargs,
> > diff --git a/hw/ppc/spapr_pci_vfio.c b/hw/ppc/spapr_pci_vfio.c
> > index b61923c..a08292a 100644
> > --- a/hw/ppc/spapr_pci_vfio.c
> > +++ b/hw/ppc/spapr_pci_vfio.c
> > @@ -24,29 +24,11 @@
> >  #include "hw/vfio/vfio.h"
> >  #include "hw/vfio/vfio-eeh.h"
> >  
> > -#include "hw/vfio/vfio-common.h"
> > -
> >  static Property spapr_phb_vfio_properties[] = {
> >      DEFINE_PROP_INT32("iommu", sPAPRPHBVFIOState, iommugroupid, -1),
> >      DEFINE_PROP_END_OF_LIST(),
> >  };
> >  
> > -int spapr_phb_check_vfio_group(sPAPRPHBState *phb, VFIOGroup **gpp)
> > -{
> > -    VFIOGroup *group;
> > -
> > -    if (!object_dynamic_cast(OBJECT(phb), "spapr-pci-vfio-host-bridge")) {
> > -        return RTAS_OUT_PARAM_ERROR;
> > -    }
> > -
> > -    /* FIXME: this is an abstraction violation */
> > -    group = vfio_get_group(SPAPR_PCI_VFIO_HOST_BRIDGE(phb)->iommugroupid,
> > -                           &phb->iommu_as);
> > -    if (gpp)
> > -        *gpp = group;
> > -    return RTAS_OUT_SUCCESS;
> > -}
> > -
> >  static void spapr_phb_vfio_finish_realize(sPAPRPHBState *sphb, Error 
> > **errp)
> >  {
> >      sPAPRPHBVFIOState *svphb = SPAPR_PCI_VFIO_HOST_BRIDGE(sphb);
> > diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
> > index 535e5ef..8c8d187 100644
> > --- a/include/hw/pci-host/spapr.h
> > +++ b/include/hw/pci-host/spapr.h
> > @@ -138,7 +138,6 @@ void spapr_pci_msi_init(sPAPRMachineState *spapr, 
> > hwaddr addr);
> >  
> >  void spapr_pci_rtas_init(void);
> >  
> > -int spapr_phb_check_vfio_group(sPAPRPHBState *phb, VFIOGroup **gpp);
> >  sPAPRPHBState *spapr_pci_find_phb(sPAPRMachineState *spapr, uint64_t buid);
> >  PCIDevice *spapr_pci_find_dev(sPAPRMachineState *spapr, uint64_t buid,
> >                                uint32_t config_addr);
> 
> 
> 

-- 
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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