Avi Kivity wrote:
On 07/27/2010 03:21 PM, Andre Przywara wrote:
Avi Kivity wrote:
On 07/27/2010 02:49 PM, Andre Przywara wrote:
What is the guest executing when it hangs?
Both VCPUs are halted, the monitor and System.map tell me it's in
native_safe_halt().
The code sequence confirms this, it is an intentional sti;hlt
condition.
Using -smp 16 also shows that all 16 VCPUs are stuck.
Well, strange. The intent of that patch was to make the clock never
go backwards. Perhaps the change made it go forwards by a large
amount, and the guest is not hung, just waiting for some timer that
is far in the future.
Can you do something like
- if (ret < last)
+ if (ret < last) {
+ static u64 max_delta;
+ if (last - ret > max_delta) {
+ max_delta = last - ret;
+ printk("advancing kvmclock by: %llx\n", max_delta);
+ }
return last;
+ }
to see if this is happening?
No change, it still hangs. I also don't see the printk.
The output with smp=1 is like this:
[ 1.186549] ACPI: Power Button [PWRF]
[ 1.189204] XENFS: not registering filesystem on non-xen platform
[ 1.195001] Non-volatile memory driver v1.3
[ 1.196358] Linux agpgart interface v0.103
[ 1.197687] [drm] Initialized drm 1.1.0 20060810
[ 1.198926] [drm:i915_init] *ERROR* drm/i915 can't work without
intel_agp module!
[ 1.201213] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
ÿ[ 1.460714] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[ 1.463243] 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[ 1.467153] brd: module loaded
[ 1.469245] loop: module loaded
With smp=2 the output stops just before the strange "y" character (I
guess it's ASCII 255), which I assume is an artifact of the serial
console.
As you can see at the timestamps, it takes some time between the last
shown line (1.201213) and the first missing one (1.460714).
Wierd. Maybe the clock goes crazy.
Let's see if it jumps forward alot:
} while (unlikely(last != ret));
+
+ {
+ static u64 last_report;
+ if (ret > last_report + 10000) {
+ last_report = ret;
+ printk("kvmclock: %llx\n", ret);
+ }
+
+ }
return ret;
}
Worth updating the 'return last' to update ret and goto the new code, so
we don't miss that path.
Did that. There is _a lot_ of output (about 350 lines per second via the
115k serial console), both with smp=1 and smp=2.
The majority is differing about 2,000,000 (ticks?), but a handful of
them are in the range of 20 million. No difference between smp=2 and smp=1.
I also get some "BUG: recent printk recursion!" and I don't see any
kernel boot progress beyond outputting the BogoMIPS value.
BTW: I found two message from your earlier debug statement:
[ 0.000000] kvm-clock: cpu 0, msr 0:1ac0401, boot clock
[ 0.000000] kvm-clock: cpu 0, msr 0:1e15401, primary cpu clock
Regards,
Andre.
--
Andre Przywara
AMD-OSRC (Dresden)
Tel: x29712
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