Re: [Xen-devel] [PATCH] x86/HVM: correct an inverted check in hvm_load()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.08.18 at 18:08, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 01/08/18 16:36, Jan Beulich wrote:
>> Clearly we want to put a vCPU to sleep if it is _not_ already down.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> ---
>> TBD: Since the flaw apparently never mattered, I imply that the function
>>      is never called with any vCPU up. Hence an alternative might be to
>>      simply return an error if a vCPU doesn't have VPF_down set.
> 
> With Remus/COLO, we should hit this path with an up vCPU on every
> iteration after the first.  Given this bug, I'm struggling to see how it
> works at all.

Well, that would rule out the alternative suggestion, but since
this is neither an ack nor a nak - what do you suggest we do?

Jan

>> --- a/xen/arch/x86/hvm/save.c
>> +++ b/xen/arch/x86/hvm/save.c
>> @@ -268,7 +268,7 @@ int hvm_load(struct domain *d, hvm_domai
>>  
>>      /* Down all the vcpus: we only re-enable the ones that had state saved. 
>> */
>>      for_each_vcpu(d, v)
>> -        if ( test_and_set_bit(_VPF_down, &v->pause_flags) )
>> +        if ( !test_and_set_bit(_VPF_down, &v->pause_flags) )
>>              vcpu_sleep_nosync(v);
>>  
>>      for ( ; ; )
>>
>>





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