Re: [PATCH] x86: kvmclock: Do not setup kvmclock vsyscall in the absence of that clock

[Jan Kiszka <jan.kiszka@web.de>]

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On 2013-02-27 12:19, Gleb Natapov wrote:
> On Sat, Feb 23, 2013 at 05:05:29PM +0100, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> This fixes boot lockups with "no-kvmclock", when the host is not
>> exposing this particular feature (QEMU: -cpu ...,-kvmclock) or when
>> the kvmclock initialization failed for whatever reason.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> Applied, thanks.

Just noticed that this fix isn't in Linus tree yet, thus also not yet in
3.8.y. Which route does it take?

Jan

> 
>> ---
>>
>> Should go to 3.8 as well, I presume.
>>
>>  arch/x86/kernel/kvmclock.c |    9 ++++++++-
>>  1 files changed, 8 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
>> index 5bedbdd..b730efa 100644
>> --- a/arch/x86/kernel/kvmclock.c
>> +++ b/arch/x86/kernel/kvmclock.c
>> @@ -160,8 +160,12 @@ int kvm_register_clock(char *txt)
>>  {
>>  	int cpu = smp_processor_id();
>>  	int low, high, ret;
>> -	struct pvclock_vcpu_time_info *src = &hv_clock[cpu].pvti;
>> +	struct pvclock_vcpu_time_info *src;
>> +
>> +	if (!hv_clock)
>> +		return 0;
>>  
>> +	src = &hv_clock[cpu].pvti;
>>  	low = (int)__pa(src) | 1;
>>  	high = ((u64)__pa(src) >> 32);
>>  	ret = native_write_msr_safe(msr_kvm_system_time, low, high);
>> @@ -276,6 +280,9 @@ int __init kvm_setup_vsyscall_timeinfo(void)
>>  	struct pvclock_vcpu_time_info *vcpu_time;
>>  	unsigned int size;
>>  
>> +	if (!hv_clock)
>> +		return 0;
>> +
>>  	size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
>>  
>>  	preempt_disable();
>> -- 
>> 1.7.3.4
>>


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