Re: [Qemu-devel] [Qemu-ppc] [PATCH v2 1/3] VFIO: Clear stale MSIx table during EEH reset

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

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On Thu, Mar 26, 2015 at 11:53:48AM +1100, Gavin Shan wrote:
> On Tue, Mar 24, 2015 at 06:53:29AM -0600, Alex Williamson wrote:
> >On Tue, 2015-03-24 at 17:54 +1100, David Gibson wrote:
> >> On Tue, Mar 24, 2015 at 05:24:55PM +1100, Gavin Shan wrote:
> >> > On Tue, Mar 24, 2015 at 04:41:21PM +1100, David Gibson wrote:
> >> > >On Mon, Mar 23, 2015 at 04:25:10PM +1100, Gavin Shan wrote:
> >> > >> On Mon, Mar 23, 2015 at 04:06:56PM +1100, David Gibson wrote:
> >> > >> >On Fri, Mar 20, 2015 at 05:27:29PM +1100, Gavin Shan wrote:
> >> > >> >> On Fri, Mar 20, 2015 at 05:04:01PM +1100, David Gibson wrote:
> >> > >> >> >On Tue, Mar 17, 2015 at 03:31:24AM +1100, Gavin Shan wrote:
> >> > >> >> >> The PCI device MSIx table is cleaned out in hardware after EEH PE
> >> > >> >> >> reset. However, we still hold the stale MSIx entries in QEMU, which
> >> > >> >> >> should be cleared accordingly. Otherwise, we will run into another
> >> > >> >> >> (recursive) EEH error and the PCI devices contained in the PE have
> >> > >> >> >> to be offlined exceptionally.
> >> > >> >> >> 
> >> > >> >> >> The patch clears stale MSIx table before EEH PE reset so that MSIx
> >> > >> >> >> table could be restored properly after EEH PE reset.
> >> > >> >> >> 
> >> > >> >> >> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
> >> > >> >> >> ---
> >> > >> >> >> v2: vfio_container_eeh_event() stub for !CONFIG_PCI and separate
> >> > >> >> >>     error message for this function. Dropped vfio_put_group()
> >> > >> >> >>     on NULL group
> >> > >> >> >> ---
> >> > >> >> >>  hw/vfio/Makefile.objs  |  6 +++++-
> >> > >> >> >>  hw/vfio/common.c       |  7 +++++++
> >> > >> >> >>  hw/vfio/pci-stub.c     | 17 +++++++++++++++++
> >> > >> >> >>  hw/vfio/pci.c          | 38 ++++++++++++++++++++++++++++++++++++++
> >> > >> >> >>  include/hw/vfio/vfio.h |  2 ++
> >> > >> >> >>  5 files changed, 69 insertions(+), 1 deletion(-)
> >> > >> >> >>  create mode 100644 hw/vfio/pci-stub.c
> >> > >> >> >> 
> >> > >> >> >> diff --git a/hw/vfio/Makefile.objs b/hw/vfio/Makefile.objs
> >> > >> >> >> index e31f30e..1b8a065 100644
> >> > >> >> >> --- a/hw/vfio/Makefile.objs
> >> > >> >> >> +++ b/hw/vfio/Makefile.objs
> >> > >> >> >> @@ -1,4 +1,8 @@
> >> > >> >> >>  ifeq ($(CONFIG_LINUX), y)
> >> > >> >> >>  obj-$(CONFIG_SOFTMMU) += common.o
> >> > >> >> >> -obj-$(CONFIG_PCI) += pci.o
> >> > >> >> >> +ifeq ($(CONFIG_PCI), y)
> >> > >> >> >> +obj-y += pci.o
> >> > >> >> >> +else
> >> > >> >> >> +obj-y += pci-stub.o
> >> > >> >> >> +endif
> >> > >> >> >>  endif
> >> > >> >> >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >> > >> >> >> index 148eb53..ed07814 100644
> >> > >> >> >> --- a/hw/vfio/common.c
> >> > >> >> >> +++ b/hw/vfio/common.c
> >> > >> >> >> @@ -949,7 +949,14 @@ int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
> >> > >> >> >>      switch (req) {
> >> > >> >> >>      case VFIO_CHECK_EXTENSION:
> >> > >> >> >>      case VFIO_IOMMU_SPAPR_TCE_GET_INFO:
> >> > >> >> >> +        break;
> >> > >> >> >>      case VFIO_EEH_PE_OP:
> >> > >> >> >> +        if (vfio_container_eeh_event(as, groupid, param) != 0) {
> >> > >> >> >
> >> > >> >> >I really dislike the idea of having an arbitrarily complex side effect
> >> > >> >> >from a function whose name suggest's it's just a trivial wrapper
> >> > >> >> >around the ioctl().
> >> > >> >> >
> >> > >> >> 
> >> > >> >> Ok. I guess you would like putting the complex in the callers of
> >> > >> >> vfio_container_ioctl().
> >> > >> >
> >> > >> >Well.. maybe.  I'd also be happy if helper functions were implemeneted
> >> > >> >which both called the ioctl() and did the other necessary pieces.
> >> > >> >They should just be called something that indicates their full
> >> > >> >function, not a name which suggests they're just an ioctl wrapper.
> >> > >> >
> >> > >> 
> >> > >> Indeed, vfio_container_ioctl() isn't indicating what the function is doing.
> >> > >> How about renaming it to vfio_container_event_and_ioctl()? I'm always bad
> >> > >> at giving a good function name :)
> >> > >
> >> > >Well, I don't think your wrapper should be multiplexed.  The multiplex
> >> > >works for the simple ioctl() wrapper, because there really is nothing
> >> > >that varies apart from the exact ioctl number called.
> >> > >
> >> > >But now that you have different operations here, I think you want
> >> > >wrappers for each one - each one will call the ioctl(), then do the
> >> > >specific extra steps necessary for that operation.  So
> >> > >vfio_container_event() will go away as well, split into various other
> >> > >functions.
> >> > >
> >> > 
> >> > It wouldn't a good idea if I understand your proposal correctly. Currnetly,
> >> > the global function vfio_container_ioctl() can be called from sPAPR platform
> >> > for any ioctl commands handled in kernel source file vfio_iommu_spapr_tce.c,
> >> > which means the function isn't called for EEH only. Other sPAPR TCE container
> >> > ioctl commands are also routed by this function. There will be lots if having
> >> > one global function for each ioctl commands, which just improve the cost to
> >> > maintain the code.
> >> 
> >> I don't really follow your objection.  I'm only suggesting separate
> >> wrappers for things which require extra actions currently implemented
> >> in vfio_container_event().  Things which only ned the plain ioctl()
> >> can still use the simple vfio_container_ioctl() wrapper.
> >
> >vfio_container_ioctl() also filters to a limited set of ioctls, it
> >clearly does not allow any ioctl.
> >
> 
> Ok. I think your guys expect something like follows. Note that the following
> vfio_container_eeh_ioctl() will accept a limited set of EEH operations, similar
> to what's doing in vfio_contain_ioctl() to the ioctl commands:
> 
> If you agree to have the changes, I'll put another patch on top of this one
> to replace vfio_container_ioctl() in spapr_pci_vfio.c with vfio_container_eeh_ioctl()
> for EEH cases.
> 
> int vfio_container_eeh_ioctl(AddressSpace *as, int32_t groupid,
>                              struct vfio_eeh_pe_op *op)
> {
>     switch (op->op) {
>     case VFIO_EEH_PE_RESET_HOT:
>     case VFIO_EEH_PE_RESET_FUNDAMENTAL: {
>         VFIOGroup *group;
>         VFIODevice *vbasedev;
>         VFIOPCIDevice *vdev;
> 
>         /*
>          * The MSIx table will be cleaned out by reset. We need
>          * disable it so that it can be reenabled properly. Also,
>          * the cached MSIx table should be cleared as it's not
>          * reflecting the contents in hardware.
>          */
>         group = vfio_get_group(groupid, as);
>         if (!group) {
>             error_report("vfio: group %d not found\n", groupid);
>             return -1;
>         }
> 
>         QLIST_FOREACH(vbasedev, &group->device_list, next) {
>             vdev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
>             if (msix_enabled(&vdev->pdev)) {
>                 vfio_disable_msix(vdev);
>             }
> 
>             msix_reset(&vdev->pdev);
>         }
> 
>         vfio_put_group(group);
> 
>         break;
>     }
>     case VFIO_EEH_PE_DISABLE:
>     case VFIO_EEH_PE_ENABLE:
>     case VFIO_EEH_PE_UNFREEZE_IO:
>     case VFIO_EEH_PE_UNFREEZE_DMA:
>     case VFIO_EEH_PE_GET_STATE:
>     case VFIO_EEH_PE_RESET_DEACTIVATE:
>     case VFIO_EEH_PE_CONFIGURE:
>         break;
>     default:
>         error_report("vfio: unsupported EEH operation %X\n", op->op);
>         return -1;
>     }
> 
>     return vfio_container_ioctl(as, groupid, VFIO_EEH_PE_OP, op);
> }


No, extra operation specific logic inside the ioctl wrapper is exactly
what I want to avoid.  Instead I want to see
vfio_container_eeh_ioctl() remain as it is now - doing nothing but
verifying the ioctl() number, then passing the arguments on to
ioctl().

What I'm expecting is then to add a new functions, along the lines of:

int vfio_eeh_pe_reset(...)
{
    VFIOGroup *group;
    VFIODevice *vbasedev;
    VFIOPCIDevice *vdev;

    /*
     * The MSIx table will be cleaned out by reset. We need
     * disable it so that it can be reenabled properly. Also,
     * the cached MSIx table should be cleared as it's not
     * reflecting the contents in hardware.
     */
    group = vfio_get_group(groupid, as);
    if (!group) {
        error_report("vfio: group %d not found\n", groupid);
        return -1;
    }

    QLIST_FOREACH(vbasedev, &group->device_list, next) {
        vdev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
        if (msix_enabled(&vdev->pdev)) {
            vfio_disable_msix(vdev);
        }

        msix_reset(&vdev->pdev);
    }

    vfio_put_group(group);

    return vfio_eeh_container_ioctl(as, groupid,
                                    VFIO_EEH_PE_RESET_FUNDAMENTAL, op);
}

I this function can build the op structure itself from sensible
arguments, then that's even better.

-- 
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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