On 05/12/2017 03:12 AM, David Gibson wrote:
On Fri, May 05, 2017 at 05:47:44PM -0300, Daniel Henrique Barboza wrote:
To allow for a DIMM unplug event to resume its work if a migration
occurs in the middle of it, this patch migrates the non-empty
pending_dimm_unplugs QTAILQ that stores the DIMM information
that the spapr_lmb_release() callback uses.
It was considered an apprach where the DIMM states would be restored
on the post-_load after a migration. The problem is that there is
no way of knowing, from the sPAPRMachineState, if a given DIMM is going
through an unplug process and the callback needs the updated DIMM State.
We could migrate a flag indicating that there is an unplug event going
on for a certain DIMM, fetching this information from the start of the
spapr_del_lmbs call. But this would also require a scan on post_load to
figure out how many nr_lmbs are left. At this point we can just
migrate the nr_lmbs information as well, given that it is being calculated
at spapr_del_lmbs already, and spare a scanning/discovery in the
post-load. All that we need is inside the sPAPRDIMMState structure
that is added to the pending_dimm_unplugs queue at the start of the
spapr_del_lmbs, so it's convenient to just migrated this queue it if it's
not empty.
Signed-off-by: Daniel Henrique Barboza <danie...@linux.vnet.ibm.com>
NACK.
As I believe I suggested previously, you can reconstruct this state on
the receiving side by doing a full scan of the DIMM and LMB DRC states.
Just had an idea that I think it's in the line of what you're
suggesting. Given
that the information we need is only created in the spapr_del_lmbs
(as per patch 1), we can use the absence of this information in the
release callback as a sort of a flag, an indication that a migration got
in the way and we need to reconstruct the nr_lmbs states again, using
the same scanning function I've used in v8.
The flow would be like this (considering the changes in the
previous 3 patches so far):
------------
/* Callback to be called during DRC release. */
void spapr_lmb_release(DeviceState *dev)
{
HotplugHandler *hotplug_ctrl;
uint64_t addr = spapr_dimm_get_address(PC_DIMM(dev));
sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
sPAPRDIMMState *ds = spapr_pending_dimm_unplugs_find(spapr, addr);
// no DIMM state found in spapr - re-create it to find out how may
LMBs are left
if (ds == NULL) {
uint32 nr_lmbs = ***call_scanning_LMB_DRCs_function(dev)***
// recreate the sPAPRDIMMState element and add it back to spapr
}
( resume callback as usual )
-----------
Is this approach be adequate? Another alternative would be to use another
way of detecting if an LMB unplug is happening and, if positive, do the same
process in the post_load(). In this case I'll need to take a look in the
code and
see how we can detect an ongoing unplug besides what I've said above.
Thanks,
Daniel
---
hw/ppc/spapr.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e190eb9..30f0b7b 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1437,6 +1437,36 @@ static bool version_before_3(void *opaque, int
version_id)
return version_id < 3;
}
+static bool spapr_pending_dimm_unplugs_needed(void *opaque)
+{
+ sPAPRMachineState *spapr = (sPAPRMachineState *)opaque;
+ return !QTAILQ_EMPTY(&spapr->pending_dimm_unplugs);
+}
+
+static const VMStateDescription vmstate_spapr_dimmstate = {
+ .name = "spapr_dimm_state",
+ .version_id = 1,
+ .minimum_version_id = 1,
+ .fields = (VMStateField[]) {
+ VMSTATE_UINT64(addr, sPAPRDIMMState),
+ VMSTATE_UINT32(nr_lmbs, sPAPRDIMMState),
+ VMSTATE_END_OF_LIST()
+ },
+};
+
+static const VMStateDescription vmstate_spapr_pending_dimm_unplugs = {
+ .name = "spapr_pending_dimm_unplugs",
+ .version_id = 1,
+ .minimum_version_id = 1,
+ .needed = spapr_pending_dimm_unplugs_needed,
+ .fields = (VMStateField[]) {
+ VMSTATE_QTAILQ_V(pending_dimm_unplugs, sPAPRMachineState, 1,
+ vmstate_spapr_dimmstate, sPAPRDIMMState,
+ next),
+ VMSTATE_END_OF_LIST()
+ },
+};
+
static bool spapr_ov5_cas_needed(void *opaque)
{
sPAPRMachineState *spapr = opaque;
@@ -1535,6 +1565,7 @@ static const VMStateDescription vmstate_spapr = {
.subsections = (const VMStateDescription*[]) {
&vmstate_spapr_ov5_cas,
&vmstate_spapr_patb_entry,
+ &vmstate_spapr_pending_dimm_unplugs,
NULL
}
};
