Quoting Michael Roth (2015-09-08 16:03:56) > Quoting David Gibson (2015-09-07 20:22:50) > > On Mon, Sep 07, 2015 at 11:37:04AM +0530, Bharata B Rao wrote: > > > When drmgr is run in the guest to add a device for which device_add > > > hasn't been issued in QEMU, configure-connector call fails. > > > When configure-connector call fails, the guest would release (*) > > > the previously acquired DRC by setting back the DRC isolation state > > > to ISOLATED and allocation state to UNUSABLE. These calls will be issued > > > only if get-sensor-state call returns PRESENT state. However currently for > > > a logical DR, entity_sense() would unconditinally return UNUSABLE > > > state only. This prevents any subsequent hotplug of the device with > > > that DRC. > > This seems a little odd. I think we default to ALLOCATION_STATE_UNUSABLE > for logical DR, and it's up the guest to transition to USABLE, which > probably happens prior to the configure-connector calls. So I think the > net effect of this fix is that guest will see these unallocated/unattached > resources the same way they would a resource that was actually attached > via device_add, and all we're really doing is working around the > eventual configuration failure that that will lead to by pretending a > resource was actually there. > > According to PAPR+ 2.7: > > 13.7.3.1 Acquire Logical Resource from Resource Pool: > > If the state is “unusable” the OS issues set-indicator (allocation-state, > usable) to attempt to allocate the re- > source. Similarly, if the state is “available for exchange” the OS issues > set-indicator (allocation-state, ex- > change) to attempt to allocate the resource, and if the state is “available > for recovery” the OS issues > set-indicator (allocation-state, recover) to attempt to allocate the > resource. > > and > > 13.7 Logical Resource Dynamic Reconfiguration (LRDR): > > The OS may use the get-sensor-state RTAS call with the dr-entity-sense > token to deter- > mine if a given drc-index refers to a connector that is currently usable for > DR operations. If the connector is not > currently usable the return state is “DR entity unusable” (2). A > set-indicator (isolation state) RTAS call to an unusable > connector or (dr-indicator) to any logical resource connector results in a > “No such indicator implemented” return sta- > tus. > > So I think maybe the proper fix is to make sure that > drc->set_indicator_state() fails with an error that indicates to RTAS to > return NO_SENSOR (-3) for cases where we haven't attached a resource > to the DRC via device_add.
Patch incoming: spapr_drc: don't allow 'empty' DRCs to be unisolated applies to spapr-next but requires revert of this patch. Bharata, can you give it a spin with CPU hotplug and see if it fixes the issue you hit? > > Which also kind of re-opens the discussion of whether or not > drc->set_indicator_state() should return RTAS errors directly. I'd > still stray away from that for now but maybe if we get more cases > like this it'll start becoming more practical. I'm starting to second-guess myself on this. I'm trying to maintain separation between RTAS/DRC but result is a bit pathological. Feel free to comment in the above patch. Just FYI: original author names appear to have gotten lost in recent spapr-next rebase. > > > > > > > Fix this by returning the right state in entity_sense() by checking > > > the allocation_state of DRC. > > > > > > (*) > > > https://lists.ozlabs.org/pipermail/linuxppc-dev/2015-September/133430.html > > > > > > Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com> > > > Cc: Michael Roth <mdr...@linux.vnet.ibm.com> > > > > Reviewed-by: David Gibson <da...@gibson.dropbear.id.au> > > > > and applied to my tree. > > > > > --- > > > hw/ppc/spapr_drc.c | 6 +++++- > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c > > > index 9ce844a..2586065 100644 > > > --- a/hw/ppc/spapr_drc.c > > > +++ b/hw/ppc/spapr_drc.c > > > @@ -186,7 +186,11 @@ static sPAPRDREntitySense > > > entity_sense(sPAPRDRConnector *drc) > > > */ > > > state = SPAPR_DR_ENTITY_SENSE_EMPTY; > > > } else { > > > - state = SPAPR_DR_ENTITY_SENSE_UNUSABLE; > > > + if (drc->allocation_state == > > > SPAPR_DR_ALLOCATION_STATE_UNUSABLE) { > > > + state = SPAPR_DR_ENTITY_SENSE_UNUSABLE; > > > + } else { > > > + state = SPAPR_DR_ENTITY_SENSE_PRESENT; > > > + } > > > } > > > } > > > > > > > -- > > 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 > >
