QEMU will hang when fed the following command-line
qemu-system-mips -kernel vmlinux-2.6.32-5-4kc-malta -append "console=ttyS0" -nographic -net none
The -net none is important otherwise it seems some events are generated
causing the things to work. When it doesn't work, the guest hangs when
measuring the CPU frequency, after the following line:
[ 0.000000] NR_IRQS:256
Pressing a key on the serial port unblocks it, hinting that the problem
is due to the recent elimination of the 1 second timeout in the main
loop.
The problem is that because init_timer_alarm sets the timer's pending
flag to true, the alarm timer is never armed until after the first time
through the main loop. Thus the bug started when QEMU started testing
the pending flag in qemu_mod_timer (commit 1828be3, more alarm timer
cleanup, 2010-03-10).
But actually, it isn't true at all that a timer is pending when the
alarm timer is created, and the real bug has been latent forever: the
fix is to remove the bogus setting of pending flag.
Reported-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>
Tested-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
qemu_rearm_alarm_timer partially duplicates the code in
qemu_next_alarm_deadline to figure out if it needs to rearm the timer.
If it calls qemu_next_alarm_deadline, it always rearms the timer even if
the next deadline is INT64_MAX.
This patch simplifies the behavior of qemu_rearm_alarm_timer and removes
the duplicated code, always calling qemu_next_alarm_deadline and only
rearming the timer if the deadline is less than INT64_MAX.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Tested-by: Andreas Färber <andreas.faerber@web.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
For command line options which permit '?' meaning 'please list the
permitted values', add support for 'help' as a synonym, by abstracting
the check out into a helper function.
This change means that in some cases where we were being lazy in
our string parsing, "?junk" will now be rejected as an invalid option
rather than being (undocumentedly) treated the same way as "?".
Update the documentation to use 'help' rather than '?', since '?'
is a shell metacharacter and thus prone to fail confusingly if there
is a single character filename in the current working directory and
the '?' has not been escaped. It's therefore better to steer users
towards 'help', though '?' is retained for backwards compatibility.
We do not, however, update the output of the system emulator's -help
(or any documentation autogenerated from the qemu-options.hx which
is the source of the -help text) because libvirt parses our -help
output and will break. At a later date when QEMU provides a better
interface so libvirt can avoid having to do this, we can update the
-help text too.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Function timeSetEvent returns 0 when it fails, but it does not set
an error code which can be retrieved by GetLastError.
Therefore calling GetLastError is useless.
Signed-off-by: Stefan Weil <sw@weilnetz.de>
sys/param.h is needed for __FreeBSD_version.
Pointed out by Juergen, thanks.
Signed-off-by: Andreas Faerber <andreas.faerber@web.de>
Cc: Juergen Lock <nox@jelal.kn-bremen.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
timeSetEvent only accepts delays in the range which is returned by
timeGetDevCaps.
The lower limit is typically 1 (= 1 ms), so the constant value of 1
in the old code usually worked.
The upper limit can be as low as 10000 ms, so the latest changes in
QEMU's timer handling which introduced timeout values above that limit
could result in failures of timeSetEvent when the timer was re-armed.
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Remove all holes which were found by pahole on Linux x86_64
(and replace "struct QEMUTimer" by "QEMUTimer").
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Some time ago, the last time which did not have dynticks was removed,
so now all timers have dynticks.
I also removed a misleading error message for the dynticks timer.
If timer_create fails, there is already an error message, and
QEMU will use the unix timer which also provides dynamic ticks,
therefore dynamic ticks are not disabled.
v2:
Remove two if statements because they were always true
(thanks to Paolo Bonzini for this correction).
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
This avoids conversions between int and bool / char.
It also makes the code more readable.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
The last user of this function was removed by commit
12d4536f7d.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
qemu-timer.h includes qemu-common.h which already includes time.h,
sys/time.h, windows.h, unistd.h, fcntl.h, errno.h and signal.h.
Therefore those include statements are redundant and can be removed.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
- remove qemu_calculate_timeout;
- explicitly size timeout to uint32_t;
- introduce slirp_update_timeout;
- pass NULL as timeout argument to select in case timeout is the maximum
value;
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Paul Brook <paul@codesourcery.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Also delta in qemu_next_alarm_deadline is a 64 bit value so set the
default to INT64_MAX instead of INT32_MAX.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Fix win32_rearm_timer and mm_rearm_timer: they should be able to handle
INT64_MAX as a delta parameter without overflowing.
Also, the next deadline in ms should be calculated rounding down rather
than up (see unix_rearm_timer and dynticks_rearm_timer).
Finally ChangeTimerQueueTimer takes an unsigned long and timeSetEvent
takes an unsigned int as delta, so cast the ms delta to the appropriate
unsigned integer.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Basically, the main wait loop calls qemu_run_all_timers() unconditionally. The
first thing this routine used to do is to see if a timer had been serviced,
and then reset the loop timeout to the next deadline.
However, the new deadlines had not been calculated at that point, as
qemu_run_timers() had not been called yet for each of the clocks. So
qemu_rearm_alarm_timer() would end up with a negative or zero deadline, and
default to setting a 250us timeout for the loop.
As qemu_run_timers() is called for each clock, the real deadlines would be put
in place, but because a loop timeout was already set, the loop timeout would
not be changed.
Once that 250us timeout fired, the real deadline would be used for the
subsequent timeout.
For idle VMs, this effectively doubles the number of times through the loop,
doubling the number of select() system calls, timer calls, etc. putting added
scheduling pressure on the kernel. And under cgroups, this really causes a big
problem because the cgroup code does not scale well.
By simply running the timers before trying to rearm the timer, we always rearm
with a non-zero deadline, effectively halving the number of system calls.
Signed-off-by: Peter Portante <pportant@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This patch combines qtest and -icount together to turn the vm_clock
into a source that can be fully managed by the client. To this end new
commands clock_step and clock_set are added. Hooking them with libqtest
is left as an exercise to the reader.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Notifiers do not need to access both ends of the list, and using
a QLIST also simplifies the API.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
The non-dynticks timer variations are broken, so they can be
removed.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
These will be used when moving icount accounting to cpus.c.
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Today, when notifying a VM state change with vm_state_notify(),
we pass a VMSTOP macro as the 'reason' argument. This is not ideal
because the VMSTOP macros tell why qemu stopped and not exactly
what the current VM state is.
One example to demonstrate this problem is that vm_start() calls
vm_state_notify() with reason=0, which turns out to be VMSTOP_USER.
This commit fixes that by replacing the VMSTOP macros with a proper
state type called RunState.
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Enabling the I/O thread by default seems like an important part of declaring
1.0. Besides allowing true SMP support with KVM, the I/O thread means that the
TCG VCPU doesn't have to multiplex itself with the I/O dispatch routines which
currently requires a (racey) signal based alarm system.
I know there have been concerns about performance. I think so far the ones that
have come up (virtio-net) are most likely due to secondary reasons like
decreased batching.
I think we ought to force enabling I/O thread early in 1.0 development and
commit to resolving any lingering issues.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Derived from kvm-tool patch
http://thread.gmane.org/gmane.comp.emulators.kvm.devel/74309
Ingo Molnar pointed out that sending the timer signal to the whole
process, just blocking it everywhere, is suboptimal with an increasing
number of threads. QEMU is also using this pattern so far.
Linux provides a (non-portable) way to restrict the signal to a single
thread: We can use SIGEV_THREAD_ID unless we are forced to emulate
signalfd via an additional thread. That case could theoretically be
optimized as well, but it doesn't look worth bothering.
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
QEMU_CLOCK_HOST is based on the system time which may jump backward in
case the admin or NTP adjusts it. RTC emulations and other device models
can suffer in this case as timers will stall for the period the clock
was tuned back.
This adds a detection mechanism that checks on every host clock readout
if the new time is before the last result. If that is the case a
notifier list is informed. Device models interested in this event can
register a notifier with the clock.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
A timer that wakes up every millisecond puts a lot of stress on the
iothread. The large amount of IPIs causes very high context switch
activity, making emulation slow and the UI unusable. This is by the
way the same reason why the Windows timers were switched to dynticks.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
dynticks will provide equally good timer granularity on all modern Linux
systems. This is more or less dead code these days.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Commit 68c23e5520 removed the
multimedia timer, but this timer is needed for certain
Linux kernels. Otherwise Linux boot stops with this error:
MP-BIOS bug: 8254 timer not connected to IO-APIC
So the multimedia timer is added again here.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
The type casts are no longer needed after some small changes
in struct qemu_alarm_timer. This also improves readability
of the code.
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
It is purely for icount-based virtual timers. And now that we got the
code right, rename the function to clarify the intended scope.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
This reverts commits 225d02cd and c9f7383c. While some parts of
the latter could be saved, I preferred a smooth, complete revert.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
The previous patch however is not enough, because if the virtual CPU
goes to sleep waiting for a future timer interrupt to wake it up, qemu
deadlocks. The timer interrupt never comes because time is driven by
icount, but the vCPU doesn't run any insns.
You could say that VCPUs should never go to sleep in icount
mode if there is a pending vm_clock timer; rather time should
just warp to the next vm_clock event with no sleep ever taking place.
Even better, you can sleep for some time related to the
time left until the next event, to avoid that the warps are too visible
externally; for example, you could be sending network packets continously
instead of every 100ms.
This is what this patch implements. qemu_clock_warp is called: 1)
whenever a vm_clock timer is adjusted, to ensure the warp_timer is
synchronized; 2) at strategic points in the CPU thread, to make sure
the insn counter is synchronized before the CPU starts running.
In any case, the warp_timer is disabled while the CPU is running,
because the insn counter will then be making progress on its own.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
These patches are already not doing a great service to out-of-tree
modifications to QEMU. However, at least we can warn them by getting
rid of the old confusing functions, or otherwise causing compilation
errors. This patch removes qemu_get_clock; the previous one changed
qemu_new_timer's signature.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This enables rt_clock timers to use nanosecond resolution, just by
using the _ns functions; there is really no reason to forbid that.
Migrated timers are all using vm_clock (of course; but I checked that
anyway) so the timers in the savevm files are already in nanosecond
resolution. So this patch makes no change to the migration format.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This was done with:
sed -i 's/qemu_get_clock\>/qemu_get_clock_ns/' \
$(git grep -l 'qemu_get_clock\>' )
sed -i 's/qemu_new_timer\>/qemu_new_timer_ns/' \
$(git grep -l 'qemu_new_timer\>' )
after checking that get_clock and new_timer never occur twice
on the same line. There were no missed occurrences; however, even
if there had been, they would have been caught by the compiler.
There was exactly one false positive in qemu_run_timers:
- current_time = qemu_get_clock (clock);
+ current_time = qemu_get_clock_ns (clock);
which is of course not in this patch.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This was done with:
sed -i '/get_clock\>.*rt_clock/s/get_clock\>/get_clock_ms/' \
$(git grep -l 'get_clock\>.*rt_clock' )
sed -i '/new_timer\>.*rt_clock/s/new_timer\>/new_timer_ms/' \
$(git grep -l 'new_timer\>.*rt_clock' )
after checking that get_clock and new_timer never occur twice
on the same line. There were no missed occurrences; however, even
if there had been, they would have been caught by the compiler.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Multimedia timers are only useful for compatibility with Windows NT 4.0
and earlier. Plus, the implementation in Wine is extremely heavyweight.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
The !use_icount code is the same for iothread and non-iothread,
except that the timeout is different. Since the timeout might as
well be infinite and is only masking bugs, use the higher value.
With this change the !use_icount code is handled equivalently
in qemu_icount_delta and qemu_calculate_timeout, and we rip it
out of the former.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@petalogix.com>
qemu_next_alarm_deadline() is needed by MinGW, too.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This patch shows how using the correct formula for
qemu_next_deadline_dyntick can simplify the code of
host_alarm_handler and eliminate useless duplication.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Paolo Bonzini
Stefano Stabellini
Peter Maydell
Stefan Weil
Andreas Faerber
Peter Portante
Luiz Capitulino
Anthony Liguori
Jan Kiszka
Stefan Weil