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

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

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);
}

Thanks,
Gavin

>> > Alternatively, we might expose another function vfio_container_eeh_ioctl(),
>> > which calls vfio_container_ioctl() after doing what we did in vfio_container_event()
>> > if necessary.
>> > 
>> > Thanks,
>> > Gavin
>> > 
>> > 
>> > 
>> 
>
>
>