Subject: [PATCH] ARM/ARM64: arch-timer: fix arch_timer_probed logic

From: [email-masked] (Daniel Lezcano)
Date: Tue, 21 Oct 2014 13:12:34 +0200

On 10/21/2014 01:07 PM, Mark Rutland wrote:
> Hi Daniel,
>
> On Tue, Oct 21, 2014 at 11:58:29AM +0100, Daniel Lezcano wrote:
>> On 10/15/2014 05:06 PM, Marc Zyngier wrote:
>>> Commit c387f07e6205 (clocksource: arm_arch_timer: Discard unavailable
>>> timers correctly) changed the way the driver makes sure both the memory
>>> and system-register timers have been probed before finalizing the probing.
>>>
>>> There is a interesting flaw in this logic that leads to this final step
>>> never to be executed. Things seems to work pretty well until something
>>> actually needs the data that is produced during this final stage.
>>>
>>> For example, KVM explodes on the first run of a guest when executed on
>>> a platform that has both memory and sysreg nodes (Juno, for example).
>>>
>>> Just fix the damned logic, and enjoy booting VMs again.
>>>
>>> Tested on a Juno system.
>>>
>>> Cc: Sudeep Holla <[email-masked]>
>>> Cc: Stephen Boyd <[email-masked]>
>>> Cc: Mark Rutland <[email-masked]>
>>> Cc: Daniel Lezcano <[email-masked]>
>>> Cc: Christoffer Dall <[email-masked]>
>>> Reported-by: Riku Voipio <[email-masked]>
>>> Signed-off-by: Marc Zyngier <[email-masked]>
>>> ---
>>
>> Applied to my tree. Also for -next.
>
> Is this going to hit -rc2? This was a regression introduced in -rc1.
>
> Without this fix we've also lost our high precision sched_clock on arm64
> platforms.
>

Sure.

Thomas or Ingo,

is it possible to update the tip/urgent branch, so I can send the fixes 
against 3.18-rc1 ?

Thanks in advance

   -- Daniel

>>>    drivers/clocksource/arm_arch_timer.c | 6 +++---
>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
>>> index 2133f9d..43005d4 100644
>>> --- a/drivers/clocksource/arm_arch_timer.c
>>> +++ b/drivers/clocksource/arm_arch_timer.c
>>> @@ -660,11 +660,11 @@ static bool __init
>>>    arch_timer_probed(int type, const struct of_device_id *matches)
>>>    {
>>>    	struct device_node *dn;
>>> -	bool probed = false;
>>> +	bool probed = true;
>>>
>>>    	dn = of_find_matching_node(NULL, matches);
>>> -	if (dn && of_device_is_available(dn) && (arch_timers_present & type))
>>> -		probed = true;
>>> +	if (dn && of_device_is_available(dn) && !(arch_timers_present & type))
>>> +		probed = false;
>>>    	of_node_put(dn);
>>>
>>>    	return probed;
>>>
>>
>>
>> --
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>>

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