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From 43f0b133d1312d042fb31bf7f63bb31a642eef26 Mon Sep 17 00:00:00 2001
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From: Laurent Vivier <lvivier@redhat.com>
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Date: Thu, 23 Nov 2017 16:14:21 +0100
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Subject: [PATCH 3/7] ppc: fix VTB migration
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RH-Author: Laurent Vivier <lvivier@redhat.com>
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Message-id: <20171123161421.30320-1-lvivier@redhat.com>
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Patchwork-id: 77796
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O-Subject: [RHV7.5 qemu-kvm-rhev PATCH] ppc: fix VTB migration
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Bugzilla: 1506882
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RH-Acked-by: Serhii Popovych <spopovyc@redhat.com>
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RH-Acked-by: David Gibson <dgibson@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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Migration of a system under stress (for example, with
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"stress-ng --numa 2") triggers on the destination
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some kernel watchdog messages like:
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NMI watchdog: BUG: soft lockup - CPU#0 stuck for 3489660870s!
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NMI watchdog: BUG: soft lockup - CPU#1 stuck for 3489660884s!
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This problem appears with the changes introduced by
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42043e4 spapr: clock should count only if vm is running
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I think this commit only triggers the problem.
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Kernel computes the soft lockup duration using the
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Virtual Timebase register (VTB), not using the Timebase
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Register (TBR, the one 42043e4 stops).
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It appears VTB is not migrated, so this patch adds it in
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the list of the SPRs to migrate, and fixes the problem.
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For the migration, I've tested a migration from qemu-2.8.0 and
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pseries-2.8.0 to a patched master (qemu-2.11.0-rc1). The received
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VTB is 0 (as is it not initialized by qemu-2.8.0), but the value
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seems to be ignored by KVM and a non zero VTB is used by the kernel.
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I have no explanation for that, but as the original problem appears
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only with SMP system under stress I suspect some problems in KVM
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(I think because VTB is shared by all threads of a core).
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Signed-off-by: Laurent Vivier <lvivier@redhat.com>
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Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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(cherry picked from commit 6dd836f5d32b989e18c6dda655a26f4d73a52f6a)
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Signed-off-by: Laurent Vivier <lvivier@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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target/ppc/translate_init.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
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index 371bbae..9d38882 100644
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--- a/target/ppc/translate_init.c
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+++ b/target/ppc/translate_init.c
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@@ -8168,10 +8168,10 @@ static void gen_spr_power8_ebb(CPUPPCState *env)
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/* Virtual Time Base */
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static void gen_spr_vtb(CPUPPCState *env)
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{
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- spr_register(env, SPR_VTB, "VTB",
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+ spr_register_kvm(env, SPR_VTB, "VTB",
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SPR_NOACCESS, SPR_NOACCESS,
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&spr_read_tbl, SPR_NOACCESS,
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- 0x00000000);
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+ KVM_REG_PPC_VTB, 0x00000000);
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}
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static void gen_spr_power8_fscr(CPUPPCState *env)
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--
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1.8.3.1
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