Re: [patch v2] virtio: console: cleanup an error message
Dan Carpenter dan.carpen...@oracle.com writes:
The PTR_ERR(NULL) here is not useful.
Signed-off-by: Dan Carpenter dan.carpen...@oracle.com
---
v2: completely different
Applied.
Thanks,
Rusty.
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 1b456fe..4cf46d8 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -2215,10 +2215,8 @@ static int __init init(void)
}
pdrvdata.debugfs_dir = debugfs_create_dir(virtio-ports, NULL);
- if (!pdrvdata.debugfs_dir) {
- pr_warning(Error %ld creating debugfs dir for virtio-ports\n,
-PTR_ERR(pdrvdata.debugfs_dir));
- }
+ if (!pdrvdata.debugfs_dir)
+ pr_warning(Error creating debugfs dir for virtio-ports\n);
INIT_LIST_HEAD(pdrvdata.consoles);
INIT_LIST_HEAD(pdrvdata.portdevs);
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Re: [PATCH v3 1/9] virtio: console: fix race with port unplug and open/close
On (Mon) 29 Jul 2013 [14:18:52], Rusty Russell wrote: Amit Shah amit.s...@redhat.com writes: There's a window between find_port_by_devt() returning a port and us taking a kref on the port, where the port could get unplugged. Fix it by taking the reference in find_port_by_devt() itself. Problem reported and analyzed by Mateusz Guzik. This fix is clearly correct, but what about the other find_port_by_* functions? They don't need a kref -- the kref is only to be bumped when: 1. Initialising / Plugging in the port (add_port) 2. Opening the port (this fix) Both these cases are now covered. As part of the locking rework, the other find_port_by_* functions may be reworked to set some state, like port_in_use, instead of abusing guest_connected today. Amit ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH] kexec/kdump implementation for Xen PV domU
On Mon, Jul 29, 2013 at 02:44:19PM -0700, Matt Wilson wrote: On Mon, Jul 29, 2013 at 07:15:43PM +0200, Daniel Kiper wrote: Hi all, Here I am sending as attachments patches enabling kexec/kdump support in Xen PV domU. Only x84_64 architecture is supported. There is no support for i386 but some code could be easily reused. Here is a description of patches: [...] - kexec-kernel-only_20121203.patch: this patch fixes timer issue on Amazon EC2 machines. Hi Daniel, Do you know the cause of this issue? Does it have something to do with singleshot timer migration when offlining/onlining SMP CPUs? Sadly, no. I was not able to replicate this on my machines (I did test on Xen 4.1). However, as I saw this issue appears on Xen 3.4 and 4.0 (IIRC version numbers used on your machines). Additionally, it does not depend on CPU models. And it appears quite often but not always. Maybe it is linked with singleshot timer migration. Daniel ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH RFC V11 15/18] kvm : Paravirtual ticketlocks support for linux guests running on KVM hypervisor
On 07/25/2013 03:08 PM, Raghavendra K T wrote:
On 07/25/2013 02:45 PM, Gleb Natapov wrote:
On Thu, Jul 25, 2013 at 02:47:37PM +0530, Raghavendra K T wrote:
On 07/24/2013 06:06 PM, Raghavendra K T wrote:
On 07/24/2013 05:36 PM, Gleb Natapov wrote:
On Wed, Jul 24, 2013 at 05:30:20PM +0530, Raghavendra K T wrote:
On 07/24/2013 04:09 PM, Gleb Natapov wrote:
On Wed, Jul 24, 2013 at 03:15:50PM +0530, Raghavendra K T wrote:
On 07/23/2013 08:37 PM, Gleb Natapov wrote:
On Mon, Jul 22, 2013 at 11:50:16AM +0530, Raghavendra K T wrote:
+static void kvm_lock_spinning(struct arch_spinlock *lock,
__ticket_t want)
[...]
+
+/*
+ * halt until it's our turn and kicked. Note that we do safe
halt
+ * for irq enabled case to avoid hang when lock info is
overwritten
+ * in irq spinlock slowpath and no spurious interrupt occur
to save us.
+ */
+if (arch_irqs_disabled_flags(flags))
+halt();
+else
+safe_halt();
+
+out:
So here now interrupts can be either disabled or enabled. Previous
version disabled interrupts here, so are we sure it is safe to
have them
enabled at this point? I do not see any problem yet, will keep
thinking.
If we enable interrupt here, then
+cpumask_clear_cpu(cpu, waiting_cpus);
and if we start serving lock for an interrupt that came here,
cpumask clear and w-lock=null may not happen atomically.
if irq spinlock does not take slow path we would have non null
value
for lock, but with no information in waitingcpu.
I am still thinking what would be problem with that.
Exactly, for kicker waiting_cpus and w-lock updates are
non atomic anyway.
+w-lock = NULL;
+local_irq_restore(flags);
+spin_time_accum_blocked(start);
+}
+PV_CALLEE_SAVE_REGS_THUNK(kvm_lock_spinning);
+
+/* Kick vcpu waiting on @lock-head to reach value @ticket */
+static void kvm_unlock_kick(struct arch_spinlock *lock,
__ticket_t ticket)
+{
+int cpu;
+
+add_stats(RELEASED_SLOW, 1);
+for_each_cpu(cpu, waiting_cpus) {
+const struct kvm_lock_waiting *w =
per_cpu(lock_waiting, cpu);
+if (ACCESS_ONCE(w-lock) == lock
+ACCESS_ONCE(w-want) == ticket) {
+add_stats(RELEASED_SLOW_KICKED, 1);
+kvm_kick_cpu(cpu);
What about using NMI to wake sleepers? I think it was
discussed, but
forgot why it was dismissed.
I think I have missed that discussion. 'll go back and check. so
what is the idea here? we can easily wake up the halted vcpus that
have interrupt disabled?
We can of course. IIRC the objection was that NMI handling path
is very
fragile and handling NMI on each wakeup will be more expensive then
waking up a guest without injecting an event, but it is still
interesting
to see the numbers.
Haam, now I remember, We had tried request based mechanism. (new
request like REQ_UNHALT) and process that. It had worked, but had
some
complex hacks in vcpu_enter_guest to avoid guest hang in case of
request cleared. So had left it there..
https://lkml.org/lkml/2012/4/30/67
But I do not remember performance impact though.
No, this is something different. Wakeup with NMI does not need KVM
changes at
all. Instead of kvm_kick_cpu(cpu) in kvm_unlock_kick you send NMI IPI.
True. It was not NMI.
just to confirm, are you talking about something like this to be
tried ?
apic-send_IPI_mask(cpumask_of(cpu), APIC_DM_NMI);
When I started benchmark, I started seeing
Dazed and confused, but trying to continue from unknown nmi error
handling.
Did I miss anything (because we did not register any NMI handler)? or
is it that spurious NMIs are trouble because we could get spurious NMIs
if next waiter already acquired the lock.
There is a default NMI handler that tries to detect the reason why NMI
happened (which is no so easy on x86) and prints this message if it
fails. You need to add logic to detect spinlock slow path there. Check
bit in waiting_cpus for instance.
aha.. Okay. will check that.
yes. Thanks.. that did the trick.
I did like below in unknown_nmi_error():
if (cpumask_test_cpu(smp_processor_id(), waiting_cpus))
return;
But I believe you asked NMI method only for experimental purpose to
check the upperbound. because as I doubted above, for spurious NMI
(i.e. when unlocker kicks when waiter already got the lock), we would
still hit unknown NMI error.
I had hit spurious NMI over 1656 times over entire benchmark run.
along with
INFO: NMI handler (arch_trigger_all_cpu_backtrace_handler) took too long
to run: 24.886 msecs etc...
(and we cannot get away with that too because it means we bypass the
unknown NMI error even in genuine cases too)
Here was the result for the my dbench test( 32 core machine with 32
vcpu guest HT off)
-- % improvement --
pvspinlock pvspin_ipi pvpsin_nmi
dbench_1x 0.9016 0.7442 0.7522
dbench_2x 14.7513 18.0164 15.9421
dbench_3x 14.7571 17.0793 13.3572
Re: Linux Plumbers ACPI/PM, PCI Microconference
On Wednesday, July 17, 2013 08:31:55 AM Shuah Khan wrote: Myron, On Tue, Jul 16, 2013 at 8:21 PM, Myron Stowe myron.st...@gmail.com wrote: Shuah - You brought up the idea about Converting drivers from Legacy PM ops to dev_pm_ops; would you like to present what you have done/encountered so far? Awesome. Yes, I would like to present what I have done so far and I do have a couple of things that could benefit from a face to face discussion which would help me make progress on the rest of the work that needs to get done. Care to sumbit a formal proposal through the LPC web page? Rafael ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: Linux Plumbers ACPI/PM, PCI Microconference
On Wed, 2013-07-31 at 00:02 +, Shuah Khan wrote: On 07/30/2013 05:38 PM, Rafael J. Wysocki wrote: On Wednesday, July 17, 2013 08:31:55 AM Shuah Khan wrote: Myron, On Tue, Jul 16, 2013 at 8:21 PM, Myron Stowe myron.st...@gmail.com wrote: Shuah - You brought up the idea about Converting drivers from Legacy PM ops to dev_pm_ops; would you like to present what you have done/encountered so far? Awesome. Yes, I would like to present what I have done so far and I do have a couple of things that could benefit from a face to face discussion which would help me make progress on the rest of the work that needs to get done. Care to sumbit a formal proposal through the LPC web page? Rafael Rafael, I did submit a formal talk proposal to LinuxCon/LPC and it was rejected. Submission is closed now as far as I know. Microconference topics should be submitted here: http://www.linuxplumbersconf.org/2013/ocw/events/LPC2013/proposals/new ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
