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hw/intc/s390_flic: Fix interrupt controller migration on s390x with TCG

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Migration of a s390x guest with TCG was long known to be very unstable,
so the tests in tests/qtest/migration-test.c are disabled if running
with TCG instead of KVM.

Nicholas Piggin did a great analysis of the problem:

"The flic pending state is not migrated, so if the machine is migrated
 while an interrupt is pending, it can be lost. This shows up in
 qtest migration test, an extint is pending (due to console writes?)
 and the CPU waits via s390_cpu_set_psw and expects the interrupt to
 wake it. However when the flic pending state is lost, s390_cpu_has_int
 returns false, so s390_cpu_exec_interrupt falls through to halting
 again."

Thus let's finally migrate the pending state, and to be on the safe
side, also the other state variables of the QEMUS390FLICState structure.

Message-ID: <20240619144421.261342-1-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This commit is contained in:
Thomas Huth 2024-06-19 16:44:21 +02:00
parent c80a339587
commit c1991c0984
3 changed files with 78 additions and 3 deletions
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1
include/hw/s390x/s390_flic.h
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@ -116,6 +116,7 @@ struct QEMUS390FLICState {
uint8_t simm;
uint8_t nimm;
QLIST_HEAD(, QEMUS390FlicIO) io[8];
bool migrate_all_state;
};
uint32_t qemu_s390_flic_dequeue_service(QEMUS390FLICState *flic);