When a KVM guest is migrated to another LPAR while a stress-ng workload is running, lockups are seen when the guest resumes on the destination LPAR. This root cause is that if there was a pending interrupt for a cpu on the source machine but it was not presented yet when the migration started, the interrupt is not retriggered on the destination LPAR. This is evident when running 'info pic' on the destination LPAR:
$ virsh qemu-monitor-command --hmp migrate 'info pic' | grep -e OS -e MSI CPU[0000]: OS 00 ff 00 ff ff 00 ff ff 80000400 CPU[0001]: OS 00 ff 00 ff ff 00 ff ff 80000401 CPU[0002]: OS 00 ff 00 ff ff 00 ff ff 80000402 CPU[0003]: OS 00 ff 00 ff ff 00 ff ff 80000403 CPU[0004]: OS 00 ff 00 ff ff 00 ff ff 80000404 CPU[0005]: OS 00 ff 00 ff ff 00 ff ff 80000405 CPU[0006]: OS 80 ff 02 ff ff 00 ff 06 80000406 CPU[0007]: OS 00 ff 00 ff ff 00 ff ff 80000407 00000000 MSI -- 00000010 0/6 3071/16384 @3710000 ^1 [ 80000010 80000010 80000010 80000010 80000010 ^00000000 ] 00000001 MSI -- 00000010 1/6 1852/16384 @3980000 ^1 [ 80000010 80000033 80000033 80000033 80000033 ^00000000 ] 00000002 MSI -- 00000010 2/6 4424/16384 @40c0000 ^1 [ 80000020 80000020 80000020 80000010 80000010 ^00000000 ] 00000003 MSI -- 00000010 3/6 1913/16384 @4220000 ^1 [ 80000010 80000032 80000010 80000010 80000010 ^00000000 ] 00000004 MSI -- 00000010 4/6 2946/16384 @4360000 ^1 [ 80000010 80000010 80000010 80000010 80000010 ^00000000 ] 00000005 MSI -- 00000010 5/6 2313/16384 @44a0000 ^1 [ 80000010 80000010 80000010 80000010 80000010 ^00000000 ] 00000006 MSI P- 00000010 6/6 5825/16384 @45f0000 ^1 [ 80000024 80000024 80000024 80000010 80000016 ^00000000 ] 00000007 MSI -- 00000010 7/6 2346/16384 @4760000 ^1 [ 80000032 80000032 80000010 80000032 80000032 ^00000000 ] Fix this by calling xive_tctx_pipr_set() in vmstate_xive_tctx_post_load(), which ends up calling qemu_irq_raise() to present the interrupt. Signed-off-by: Gautam Menghani <[email protected]> --- hw/intc/xive.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/hw/intc/xive.c b/hw/intc/xive.c index f473e6ac77..712498d4af 100644 --- a/hw/intc/xive.c +++ b/hw/intc/xive.c @@ -1080,6 +1080,9 @@ static int vmstate_xive_tctx_post_load(void *opaque, int version_id) error_report_err(local_err); return ret; } + } else { + uint8_t pipr = tctx->regs[TM_QW1_OS + TM_PIPR]; + xive_tctx_pipr_set(tctx, TM_QW1_OS, pipr, 0); } return 0; -- 2.53.0
