Re: [Xen-devel] [PATCH v2 09/12] x86/altp2m: add remaining support routines.

[Ed White <edmund.h.white@xxxxxxxxx>]

On 06/29/2015 06:03 AM, Andrew Cooper wrote:
> On 26/06/15 17:30, Ed White wrote:
>> On 06/24/2015 11:19 AM, Andrew Cooper wrote:
>>> On 24/06/15 18:47, Ed White wrote:
>>>>>> This looks like some hoop jumping around the assertions in
>>>>>> domain_pause() and vcpu_pause().
>>>>>>
>>>>>> We should probably have some new helpers where the domain needs to be
>>>>>> paused, possibly while in context.  The current domain/vcpu_pause() are
>>>>>> almost always used where it is definitely not safe to pause in context,
>>>>>> hence the assertions.
>>>>>>
>>>> It is. I'd be happy to use new helpers, I don't feel qualified to
>>>> write them.
>>>>
>>>> Ed
>>> Something like this?  Only compile tested.  In the meantime, I have an
>>> optimisation in mind for domain_pause() on domains with large numbers of
>>> vcpus, but that will have to wait a while.
>>>
>>> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> Date: Wed, 24 Jun 2015 19:06:14 +0100
>>> Subject: [PATCH] common/domain: Helpers to pause a domain while in context
>>>
>>> For use on codepaths which would need to use domain_pause() but might be in
>>> the target domain's context.  In the case that the target domain is in
>>> context,
>>> all other vcpus are paused.
>>>
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> ---
>>>  xen/common/domain.c     |   28 ++++++++++++++++++++++++++++
>>>  xen/include/xen/sched.h |    5 +++++
>>>  2 files changed, 33 insertions(+)
>>>
>>> diff --git a/xen/common/domain.c b/xen/common/domain.c
>>> index 3bc52e6..a1d27e3 100644
>>> --- a/xen/common/domain.c
>>> +++ b/xen/common/domain.c
>>> @@ -1010,6 +1010,34 @@ int domain_unpause_by_systemcontroller(struct
>>> domain *d)
>>>      return 0;
>>>  }
>>>  
>>> +void domain_pause_except_self(struct domain *d)
>>> +{
>>> +    struct vcpu *v, *curr = current;
>>> +
>>> +    if ( curr->domain == d )
>>> +    {
>>> +        for_each_vcpu( d, v )
>>> +            if ( likely(v != curr) )
>>> +                vcpu_pause(v);
>>> +    }
>>> +    else
>>> +        domain_pause(d);
>>> +}
>>> +
>>> +void domain_unpause_except_self(struct domain *d)
>>> +{
>>> +    struct vcpu *v, *curr = current;
>>> +
>>> +    if ( curr->domain == d )
>>> +    {
>>> +        for_each_vcpu( d, v )
>>> +            if ( likely(v != curr) )
>>> +                vcpu_unpause(v);
>>> +    }
>>> +    else
>>> +        domain_unpause(d);
>>> +}
>>> +
>>>  int vcpu_reset(struct vcpu *v)
>>>  {
>>>      struct domain *d = v->domain;
>>> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
>>> index b29d9e7..8e1345a 100644
>>> --- a/xen/include/xen/sched.h
>>> +++ b/xen/include/xen/sched.h
>>> @@ -804,6 +804,11 @@ static inline int
>>> domain_pause_by_systemcontroller_nosync(struct domain *d)
>>>  {
>>>      return __domain_pause_by_systemcontroller(d, domain_pause_nosync);
>>>  }
>>> +
>>> +/* domain_pause() but safe against trying to pause current. */
>>> +void domain_pause_except_self(struct domain *d);
>>> +void domain_unpause_except_self(struct domain *d);
>>> +
>>>  void cpu_init(void);
>>>  
>>>  struct scheduler;
>>>
>>>
>> Did you commit this to staging?
> 
> I am not a committer, so couldn't even if I wished to.
> 
>> IOW, can I apply it to my branch
>> and assume it will already be in-tree when our patches are applied?
> 
> You will be the first user of the patch, and as noted, I have only
> compile tested.  Please take it and put it at the start of your series.
> 

Will do. I thought you were all-powerful.

Ed

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