From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50046) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YQNT6-0005G5-2l for qemu-devel@nongnu.org; Tue, 24 Feb 2015 16:56:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YQNSu-0000cT-Mq for qemu-devel@nongnu.org; Tue, 24 Feb 2015 16:56:39 -0500 Received: from e7.ny.us.ibm.com ([32.97.182.137]:52722) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YQNSu-0000c8-JX for qemu-devel@nongnu.org; Tue, 24 Feb 2015 16:56:28 -0500 Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 24 Feb 2015 16:56:28 -0500 From: Michael Roth Date: Tue, 24 Feb 2015 15:48:18 -0600 Message-Id: <1424814498-6993-44-git-send-email-mdroth@linux.vnet.ibm.com> In-Reply-To: <1424814498-6993-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1424814498-6993-1-git-send-email-mdroth@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 43/43] exec: change default exception_index value for migration to -1 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , qemu-stable@nongnu.org, Peter Maydell From: Paolo Bonzini In QEMU 2.2 the exception_index value was added to the migration stream through a subsection. The default was set to 0, which is wrong and should have been -1. However, 2.2 does not have commit e511b4d (cpu-exec: reset exception_index correctly, 2014-11-26), hence in 2.2 the exception_index is never used and is set to -1 on the next call to cpu_exec. So we can change the migration stream to make the default -1. The effects are: - 2.2.1 -> 2.2.0: cpu->exception_index set incorrectly to 0 if it were -1 on the source; then reset to -1 in cpu_exec. This is TCG only; KVM does not use exception_index. - 2.2.0 -> 2.2.1: cpu->exception_index set incorrectly to -1 if it were 0 on the source; but it would be reset to -1 in cpu_exec anyway. This is TCG only; KVM does not use exception_index. - 2.2.1 -> 2.1: two bugs fixed: 1) can migrate backwards if cpu->exception_index is set to -1; 2) should not migrate backwards (but 2.2.0 allows it) if cpu->exception_index is set to 0 - 2.2.0 -> 2.3.0: 2.2.0 will send the subsection unnecessarily if exception_index is -1, but that is not a problem. 2.3.0 will set cpu->exception_index to -1 if it is 0 on the source, but this would be anyway a problem for 2.2.0 -> 2.2.x migration (due to lack of commit e511b4d in 2.2.x) so we can ignore it - 2.2.1 -> 2.3.0: everything works. In addition, play it safe and never send the subsection unless TCG is in use. KVM does not use exception_index (PPC KVM stores values in it for use in the subsequent call to ppc_cpu_do_interrupt, but does not need it as soon as kvm_handle_debug returns). Xen and qtest do not run any code for the CPU at all. Reported-by: Igor Mammedov Tested-by: Laurent Desnogues Tested-by: Eduardo Habkost Signed-off-by: Paolo Bonzini Message-id: 1418989994-17244-3-git-send-email-pbonzini@redhat.com Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini Signed-off-by: Peter Maydell (cherry picked from commit adee64249ee37e822d578e65a765750e7f2081f6) Signed-off-by: Michael Roth --- exec.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/exec.c b/exec.c index 71ac104..46fe70e 100644 --- a/exec.c +++ b/exec.c @@ -434,7 +434,7 @@ static int cpu_common_pre_load(void *opaque) { CPUState *cpu = opaque; - cpu->exception_index = 0; + cpu->exception_index = -1; return 0; } @@ -443,7 +443,7 @@ static bool cpu_common_exception_index_needed(void *opaque) { CPUState *cpu = opaque; - return cpu->exception_index != 0; + return tcg_enabled() && cpu->exception_index != -1; } static const VMStateDescription vmstate_cpu_common_exception_index = { -- 1.9.1