Author: avg
Date: Thu Nov 7 21:14:59 2019
New Revision: 354482
URL: https://svnweb.freebsd.org/changeset/base/354482
Log:
IPI_TRACE is not really supported on xen
x86 stack_save_td_running() can work safely only if IPI_TRACE is a
non-maskable interrupt. But at the moment FreeBSD/Xen does not provide
support for the NMI delivery mode. So, mark the functionality as
unsupported similarly to other platforms without NMI.
Maybe there is a way to provide a Xen-specific working
stack_save_td_running(), but I couldn't figure it out.
MFC after: 3 weeks
Sponsored by: Panzura
Modified:
head/sys/x86/x86/stack_machdep.c
Modified: head/sys/x86/x86/stack_machdep.c
==============================================================================
--- head/sys/x86/x86/stack_machdep.c Thu Nov 7 21:08:49 2019
(r354481)
+++ head/sys/x86/x86/stack_machdep.c Thu Nov 7 21:14:59 2019
(r354482)
@@ -135,6 +135,13 @@ int
stack_save_td_running(struct stack *st, struct thread *td)
{
+#ifdef XENHVM
+ /*
+ * There is no NMI support on Xen, so this code can lead to
+ * an inter-processor deadlock.
+ */
+ return (EOPNOTSUPP);
+#endif /* XENHVM */
#ifdef STACK
THREAD_LOCK_ASSERT(td, MA_OWNED);
MPASS(TD_IS_RUNNING(td));
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