From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37762) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZWbU-0007Au-2O for qemu-devel@nongnu.org; Wed, 09 Sep 2015 00:03:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZWbQ-0000kU-KD for qemu-devel@nongnu.org; Wed, 09 Sep 2015 00:03:24 -0400 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:35045) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZWbP-0000gh-Tf for qemu-devel@nongnu.org; Wed, 09 Sep 2015 00:03:20 -0400 Received: from /spool/local by e28smtp08.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 9 Sep 2015 09:33:16 +0530 Date: Wed, 9 Sep 2015 09:32:32 +0530 From: Bharata B Rao Message-ID: <20150909040232.GB17433@in.ibm.com> References: <1441606024-1238-1-git-send-email-bharata@linux.vnet.ibm.com> <20150908012250.GG6537@voom.redhat.com> <20150908210356.10296.36458@loki> <20150908220325.10296.24993@loki> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20150908220325.10296.24993@loki> Subject: Re: [Qemu-devel] [FIX PATCH] spapr_drc: Return correct state for logical DR in entity_sense() Reply-To: bharata@linux.vnet.ibm.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Roth Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, David Gibson On Tue, Sep 08, 2015 at 05:03:25PM -0500, Michael Roth wrote: > 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. Yes, please revert this patch in favour of Michael's. > > Bharata, can you give it a spin with CPU hotplug and see if it fixes the > issue you hit? Yes it does, thanks. Regards, Bharata.