Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Wed, Jan 25, 2023 at 10:46:58AM -0800, Paul E. McKenney wrote:
> > Ofc. Paul might have an opinion on this glorious bodge ;-)
>
> For some definition of the word "glorious", to be sure. ;-)
>
> Am I correct that you have two things happening here? (1) Preventing
> trace recursion and (2) forcing RCU to pay attention when needed.
Mostly just (1), we're in an error situation, I'm not too worried about
(2).
> I cannot resist pointing out that you have re-invented RCU_NONIDLE(),
> though avoiding much of the overhead when not needed. ;-)
Yeah, this was the absolute minimal bodge I could come up with that
shuts up the rcu_derefence warning thing.
> I would have objections if this ever leaks out onto a non-error code path.
Agreed.
> There are things that need doing when RCU starts and stops watching,
> and this approach omits those things. Which again is OK in this case,
> where this code is only ever executed when something is already broken,
> but definitely *not* OK when things are not already broken.
And agreed.
Current version of the bodge looks like so (will repost the whole series
a little later today).
I managed to tickle the recursion so that it was a test-case for the
stack guard...
With this on, it prints just the one WARN and lives.
---
Subject: bug: Disable rcu_is_watching() during WARN/BUG
From: Peter Zijlstra
Date: Wed Jan 25 13:57:49 CET 2023
In order to avoid WARN/BUG from generating nested or even recursive
warnings, force rcu_is_watching() true during
WARN/lockdep_rcu_suspicious().
Notably things like unwinding the stack can trigger rcu_dereference()
warnings, which then triggers more unwinding which then triggers more
warnings etc..
Signed-off-by: Peter Zijlstra (Intel)
---
include/linux/context_tracking.h | 27 +++
kernel/locking/lockdep.c |3 +++
kernel/panic.c |5 +
lib/bug.c| 15 ++-
4 files changed, 49 insertions(+), 1 deletion(-)
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -130,9 +130,36 @@ static __always_inline unsigned long ct_
return arch_atomic_add_return(incby,
this_cpu_ptr(&context_tracking.state));
}
+static __always_inline bool warn_rcu_enter(void)
+{
+ bool ret = false;
+
+ /*
+* Horrible hack to shut up recursive RCU isn't watching fail since
+* lots of the actual reporting also relies on RCU.
+*/
+ preempt_disable_notrace();
+ if (rcu_dynticks_curr_cpu_in_eqs()) {
+ ret = true;
+ ct_state_inc(RCU_DYNTICKS_IDX);
+ }
+
+ return ret;
+}
+
+static __always_inline void warn_rcu_exit(bool rcu)
+{
+ if (rcu)
+ ct_state_inc(RCU_DYNTICKS_IDX);
+ preempt_enable_notrace();
+}
+
#else
static inline void ct_idle_enter(void) { }
static inline void ct_idle_exit(void) { }
+
+static __always_inline bool warn_rcu_enter(void) { return false; }
+static __always_inline void warn_rcu_exit(bool rcu) { }
#endif /* !CONFIG_CONTEXT_TRACKING_IDLE */
#endif
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -55,6 +55,7 @@
#include
#include
#include
+#include
#include
@@ -6555,6 +6556,7 @@ void lockdep_rcu_suspicious(const char *
{
struct task_struct *curr = current;
int dl = READ_ONCE(debug_locks);
+ bool rcu = warn_rcu_enter();
/* Note: the following can be executed concurrently, so be careful. */
pr_warn("\n");
@@ -6595,5 +6597,6 @@ void lockdep_rcu_suspicious(const char *
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
+ warn_rcu_exit(rcu);
}
EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -34,6 +34,7 @@
#include
#include
#include
+#include
#include
#include
@@ -679,6 +680,7 @@ void __warn(const char *file, int line,
void warn_slowpath_fmt(const char *file, int line, unsigned taint,
const char *fmt, ...)
{
+ bool rcu = warn_rcu_enter();
struct warn_args args;
pr_warn(CUT_HERE);
@@ -693,11 +695,13 @@ void warn_slowpath_fmt(const char *file,
va_start(args.args, fmt);
__warn(file, line, __builtin_return_address(0), taint, NULL, &args);
va_end(args.args);
+ warn_rcu_exit(rcu);
}
EXPORT_SYMBOL(warn_slowpath_fmt);
#else
void __warn_printk(const char *fmt, ...)
{
+ bool rcu = warn_rcu_enter();
va_list args;
pr_warn(CUT_HERE);
@@ -705,6 +709,7 @@ void __warn_printk(const char *fmt, ...)
va_start(args, fmt);
vprintk(fmt, args);
va_end(args);
+ warn_rcu_exit(rcu);
}
EXPORT_SYMBOL(__warn_printk);
#endif
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -47,6 +47,7 @@
#include
#include
#include
+#include
extern struct bug_entry __start___bug_table[], __stop___bug_table[];
@@ -153,7 +154,7 @@ struct bu
Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Wed, Jan 25, 2023 at 11:47:44AM +0100, Peter Zijlstra wrote:
> On Tue, Jan 24, 2023 at 05:12:14PM +, Mark Rutland wrote:
> > On Tue, Jan 24, 2023 at 03:44:35PM +0100, Peter Zijlstra wrote:
> > > On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote:
> > >
> > > > Actually, perhaps we can just add this, and all you need to do is create
> > > > and set CONFIG_NO_RCU_TRACING (or some other name).
> > >
> > > Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this.
> >
> > Yes please; if we use CONFIG_ARCH_WANTS_NO_INSTR then arm64 will get this
> > "for
> > free" once we add the missing checks (which I assume we need) in our
> > ftrace_prepare_return().
> >
> > > Anyway, I took it for a spin and it doesn't seems to do the job.
> > >
> > > With my patch the first splat is
> > >
> > > "RCU not on for: cpuidle_poll_time+0x0/0x70"
> > >
> > > While with yours I seems to get the endless:
> > >
> > > "WARNING: suspicious RCU usage"
> > >
> > > thing. Let me see if I can figure out where it goes side-ways.
> >
> > Hmmm... for WARN_ONCE() don't we need to wake RCU first also? I thought we
> > needed that at least for the printk machinery?
>
> OK, the below seems to work nice for me -- although I'm still on a
> hacked up printk, but the recursive RCU not watching fail seems to be
> tamed.
FWIW, I gave that a spin on arm64 with the ftrace selftests, and I see no
splats, so it looks good on that front.
Currently arm64's BUG/WARN exception handling does the usual
lockdep/rcu/whatever stuff before getting to report_bug(), so that bit should
be redundant (and any WARN() or BUG() early in the entry code is likely to lead
to a stack overflow and kill the kernel), but it shouldn't be harmful.
> Ofc. Paul might have an opinion on this glorious bodge ;-)
I'll leave that to Paul. ;)
Thanks,
Mark.
>
> ---
>
> diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
> index c303f7a114e9..d48cd92d2364 100644
> --- a/include/linux/trace_recursion.h
> +++ b/include/linux/trace_recursion.h
> @@ -135,6 +135,21 @@ extern void ftrace_record_recursion(unsigned long ip,
> unsigned long parent_ip);
> # define do_ftrace_record_recursion(ip, pip) do { } while (0)
> #endif
>
> +#ifdef CONFIG_ARCH_WANTS_NO_INSTR
> +# define trace_warn_on_no_rcu(ip)\
> + ({ \
> + bool __ret = !rcu_is_watching();\
> + if (__ret && !trace_recursion_test(TRACE_RECORD_RECURSION_BIT))
> { \
> + trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \
> + WARN_ONCE(true, "RCU not on for: %pS\n", (void *)ip); \
> + trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \
> + } \
> + __ret; \
> + })
> +#else
> +# define trace_warn_on_no_rcu(ip)false
> +#endif
> +
> /*
> * Preemption is promised to be disabled when return bit >= 0.
> */
> @@ -144,6 +159,9 @@ static __always_inline int
> trace_test_and_set_recursion(unsigned long ip, unsign
> unsigned int val = READ_ONCE(current->trace_recursion);
> int bit;
>
> + if (trace_warn_on_no_rcu(ip))
> + return -1;
> +
> bit = trace_get_context_bit() + start;
> if (unlikely(val & (1 << bit))) {
> /*
> diff --git a/lib/bug.c b/lib/bug.c
> index c223a2575b72..0a10643ea168 100644
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -47,6 +47,7 @@
> #include
> #include
> #include
> +#include
>
> extern struct bug_entry __start___bug_table[], __stop___bug_table[];
>
> @@ -153,7 +154,7 @@ struct bug_entry *find_bug(unsigned long bugaddr)
> return module_find_bug(bugaddr);
> }
>
> -enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
> +static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_regs
> *regs)
> {
> struct bug_entry *bug;
> const char *file;
> @@ -209,6 +210,30 @@ enum bug_trap_type report_bug(unsigned long bugaddr,
> struct pt_regs *regs)
> return BUG_TRAP_TYPE_BUG;
> }
>
> +enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
> +{
> + enum bug_trap_type ret;
> + bool rcu = false;
> +
> +#ifdef CONFIG_CONTEXT_TRACKING_IDLE
> + /*
> + * Horrible hack to shut up recursive RCU isn't watching fail since
> + * lots of the actual reporting also relies on RCU.
> + */
> + if (!rcu_is_watching()) {
> + rcu = true;
> + ct_state_inc(RCU_DYNTICKS_IDX);
> + }
> +#endif
> +
> + ret = __report_bug(bugaddr, regs);
> +
> + if (rcu)
> + ct_state_inc(RCU_DYNTICKS_IDX);
> +
> + return ret;
> +}
> +
> static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
> {
> struct bug_entry *b
Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Tue, Jan 24, 2023 at 05:12:14PM +, Mark Rutland wrote:
> On Tue, Jan 24, 2023 at 03:44:35PM +0100, Peter Zijlstra wrote:
> > On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote:
> >
> > > Actually, perhaps we can just add this, and all you need to do is create
> > > and set CONFIG_NO_RCU_TRACING (or some other name).
> >
> > Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this.
>
> Yes please; if we use CONFIG_ARCH_WANTS_NO_INSTR then arm64 will get this "for
> free" once we add the missing checks (which I assume we need) in our
> ftrace_prepare_return().
>
> > Anyway, I took it for a spin and it doesn't seems to do the job.
> >
> > With my patch the first splat is
> >
> > "RCU not on for: cpuidle_poll_time+0x0/0x70"
> >
> > While with yours I seems to get the endless:
> >
> > "WARNING: suspicious RCU usage"
> >
> > thing. Let me see if I can figure out where it goes side-ways.
>
> Hmmm... for WARN_ONCE() don't we need to wake RCU first also? I thought we
> needed that at least for the printk machinery?
OK, the below seems to work nice for me -- although I'm still on a
hacked up printk, but the recursive RCU not watching fail seems to be
tamed.
Ofc. Paul might have an opinion on this glorious bodge ;-)
---
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index c303f7a114e9..d48cd92d2364 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -135,6 +135,21 @@ extern void ftrace_record_recursion(unsigned long ip,
unsigned long parent_ip);
# define do_ftrace_record_recursion(ip, pip) do { } while (0)
#endif
+#ifdef CONFIG_ARCH_WANTS_NO_INSTR
+# define trace_warn_on_no_rcu(ip) \
+ ({ \
+ bool __ret = !rcu_is_watching();\
+ if (__ret && !trace_recursion_test(TRACE_RECORD_RECURSION_BIT))
{ \
+ trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \
+ WARN_ONCE(true, "RCU not on for: %pS\n", (void *)ip); \
+ trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \
+ } \
+ __ret; \
+ })
+#else
+# define trace_warn_on_no_rcu(ip) false
+#endif
+
/*
* Preemption is promised to be disabled when return bit >= 0.
*/
@@ -144,6 +159,9 @@ static __always_inline int
trace_test_and_set_recursion(unsigned long ip, unsign
unsigned int val = READ_ONCE(current->trace_recursion);
int bit;
+ if (trace_warn_on_no_rcu(ip))
+ return -1;
+
bit = trace_get_context_bit() + start;
if (unlikely(val & (1 << bit))) {
/*
diff --git a/lib/bug.c b/lib/bug.c
index c223a2575b72..0a10643ea168 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -47,6 +47,7 @@
#include
#include
#include
+#include
extern struct bug_entry __start___bug_table[], __stop___bug_table[];
@@ -153,7 +154,7 @@ struct bug_entry *find_bug(unsigned long bugaddr)
return module_find_bug(bugaddr);
}
-enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
+static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_regs
*regs)
{
struct bug_entry *bug;
const char *file;
@@ -209,6 +210,30 @@ enum bug_trap_type report_bug(unsigned long bugaddr,
struct pt_regs *regs)
return BUG_TRAP_TYPE_BUG;
}
+enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
+{
+ enum bug_trap_type ret;
+ bool rcu = false;
+
+#ifdef CONFIG_CONTEXT_TRACKING_IDLE
+ /*
+* Horrible hack to shut up recursive RCU isn't watching fail since
+* lots of the actual reporting also relies on RCU.
+*/
+ if (!rcu_is_watching()) {
+ rcu = true;
+ ct_state_inc(RCU_DYNTICKS_IDX);
+ }
+#endif
+
+ ret = __report_bug(bugaddr, regs);
+
+ if (rcu)
+ ct_state_inc(RCU_DYNTICKS_IDX);
+
+ return ret;
+}
+
static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
{
struct bug_entry *bug;
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Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Tue, Jan 24, 2023 at 05:12:14PM +, Mark Rutland wrote: > On Tue, Jan 24, 2023 at 03:44:35PM +0100, Peter Zijlstra wrote: > > On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote: > > > > > Actually, perhaps we can just add this, and all you need to do is create > > > and set CONFIG_NO_RCU_TRACING (or some other name). > > > > Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this. > > Yes please; if we use CONFIG_ARCH_WANTS_NO_INSTR then arm64 will get this "for > free" once we add the missing checks (which I assume we need) in our > ftrace_prepare_return(). Aye. > > Anyway, I took it for a spin and it doesn't seems to do the job. > > > > With my patch the first splat is > > > > "RCU not on for: cpuidle_poll_time+0x0/0x70" > > > > While with yours I seems to get the endless: > > > > "WARNING: suspicious RCU usage" > > > > thing. Let me see if I can figure out where it goes side-ways. > > Hmmm... for WARN_ONCE() don't we need to wake RCU first also? I thought we > needed that at least for the printk machinery? Yeah, I'm currently running with a hacked up printk that redirects everything into early_printk() but it still trips up lots. I was just about to go stick on RCU magic into WARN itself, this isn't going to be the only site triggering this fail-cascade. ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Tue, Jan 24, 2023 at 03:44:35PM +0100, Peter Zijlstra wrote: > On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote: > > > Actually, perhaps we can just add this, and all you need to do is create > > and set CONFIG_NO_RCU_TRACING (or some other name). > > Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this. Yes please; if we use CONFIG_ARCH_WANTS_NO_INSTR then arm64 will get this "for free" once we add the missing checks (which I assume we need) in our ftrace_prepare_return(). > Anyway, I took it for a spin and it doesn't seems to do the job. > > With my patch the first splat is > > "RCU not on for: cpuidle_poll_time+0x0/0x70" > > While with yours I seems to get the endless: > > "WARNING: suspicious RCU usage" > > thing. Let me see if I can figure out where it goes side-ways. Hmmm... for WARN_ONCE() don't we need to wake RCU first also? I thought we needed that at least for the printk machinery? Thanks, Mark. ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote: > Actually, perhaps we can just add this, and all you need to do is create > and set CONFIG_NO_RCU_TRACING (or some other name). Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this. Anyway, I took it for a spin and it doesn't seems to do the job. With my patch the first splat is "RCU not on for: cpuidle_poll_time+0x0/0x70" While with yours I seems to get the endless: "WARNING: suspicious RCU usage" thing. Let me see if I can figure out where it goes side-ways. ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Mon, 23 Jan 2023 16:53:04 -0500
Steven Rostedt wrote:
> On Mon, 23 Jan 2023 21:50:12 +0100
> Peter Zijlstra wrote:
>
> > All RCU disabled code should be noinstr and hence we should never get
> > here -- when we do, WARN about it and make sure to not actually do
> > tracing.
> >
> > Signed-off-by: Peter Zijlstra (Intel)
> > ---
> > arch/x86/kernel/ftrace.c |3 +++
> > 1 file changed, 3 insertions(+)
> >
> > --- a/arch/x86/kernel/ftrace.c
> > +++ b/arch/x86/kernel/ftrace.c
> > @@ -646,6 +646,9 @@ void prepare_ftrace_return(unsigned long
> > if (unlikely(atomic_read(¤t->tracing_graph_pause)))
> > return;
> >
> > + if (WARN_ONCE(!rcu_is_watching(), "RCU not on for: %pS\n", (void *)ip))
> > + return;
> > +
>
> Please add this to after recursion trylock below. Although WARN_ONCE()
> should not not have recursion issues, as function tracing can do weird
> things, I rather be safe than sorry, and not have the system triple boot
> due to some path that might get added in the future.
>
> If rcu_is_watching() is false, it will still get by the below recursion
> check and warn. That is, the below check should be done before this
> function calls any other function.
>
> > bit = ftrace_test_recursion_trylock(ip, *parent);
> > if (bit < 0)
> > return;
> >
>
Actually, perhaps we can just add this, and all you need to do is create
and set CONFIG_NO_RCU_TRACING (or some other name).
This should cover all ftrace locations. (Uncompiled).
-- Steve
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index c303f7a114e9..10ee3fbb9113 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -135,6 +135,22 @@ extern void ftrace_record_recursion(unsigned long ip,
unsigned long parent_ip);
# define do_ftrace_record_recursion(ip, pip) do { } while (0)
#endif
+#ifdef CONFIG_NO_RCU_TRACING
+# define trace_warn_on_no_rcu(ip) \
+ ({ \
+ bool __ret = false; \
+ if (!trace_recursion_test(TRACE_RECORD_RECURSION_BIT)) { \
+ trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \
+ __ret = WARN_ONCE(!rcu_is_watching(), \
+ "RCU not on for: %pS\n", (void *)ip);
\
+ trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \
+ } \
+ __ret; \
+ })
+#else
+# define trace_warn_on_no_rcu(ip) false
+#endif
+
/*
* Preemption is promised to be disabled when return bit >= 0.
*/
@@ -144,6 +160,9 @@ static __always_inline int
trace_test_and_set_recursion(unsigned long ip, unsign
unsigned int val = READ_ONCE(current->trace_recursion);
int bit;
+ if (trace_warn_on_no_rcu(ip))
+ return -1;
+
bit = trace_get_context_bit() + start;
if (unlikely(val & (1 << bit))) {
/*
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Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
On Mon, 23 Jan 2023 21:50:12 +0100 Peter Zijlstra wrote: > All RCU disabled code should be noinstr and hence we should never get > here -- when we do, WARN about it and make sure to not actually do > tracing. > > Signed-off-by: Peter Zijlstra (Intel) > --- > arch/x86/kernel/ftrace.c |3 +++ > 1 file changed, 3 insertions(+) > > --- a/arch/x86/kernel/ftrace.c > +++ b/arch/x86/kernel/ftrace.c > @@ -646,6 +646,9 @@ void prepare_ftrace_return(unsigned long > if (unlikely(atomic_read(¤t->tracing_graph_pause))) > return; > > + if (WARN_ONCE(!rcu_is_watching(), "RCU not on for: %pS\n", (void *)ip)) > + return; > + Please add this to after recursion trylock below. Although WARN_ONCE() should not not have recursion issues, as function tracing can do weird things, I rather be safe than sorry, and not have the system triple boot due to some path that might get added in the future. If rcu_is_watching() is false, it will still get by the below recursion check and warn. That is, the below check should be done before this function calls any other function. > bit = ftrace_test_recursion_trylock(ip, *parent); > if (bit < 0) > return; > -- Steve ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
[PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
All RCU disabled code should be noinstr and hence we should never get here -- when we do, WARN about it and make sure to not actually do tracing. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/ftrace.c |3 +++ 1 file changed, 3 insertions(+) --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -646,6 +646,9 @@ void prepare_ftrace_return(unsigned long if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; + if (WARN_ONCE(!rcu_is_watching(), "RCU not on for: %pS\n", (void *)ip)) + return; + bit = ftrace_test_recursion_trylock(ip, *parent); if (bit < 0) return; ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
