Re: [PATCH RFC 1/6] public/xen.h: add flags field to vcpu_time_info

[Joao Martins <joao.m.martins@oracle.com>]

On 01/25/2016 08:11 PM, Konrad Rzeszutek Wilk wrote:
> On Mon, Dec 28, 2015 at 04:59:40PM +0000, Joao Martins wrote:
>> This field has two possible flags (as of latest pvclock ABI
>> shared with KVM).
> 
> <sigh>
> 
> Wish they had CC-ed xen-devel instead of just doing their
> change
Indeed, Andrew was suggesting that an entry could perhaps be added to the
maintainers file with xen-devel, to avoid situations like this.


>>
>> flags: bits in this field indicate extended capabilities
>> coordinated between the guest and the hypervisor.  Specifically
>> on KVM, availability of specific flags has to be checked in
>> 0x40000001 cpuid leaf. On Xen, we don't have that but we can
>> still check some of the flags after registering the time info
>> page since a force_update_vcpu_system_time is performed.
>>
>> Current flags are:
>>
>>  flag bit   | cpuid bit    | meaning
>> -------------------------------------------------------------
>>             |              | time measures taken across
>>      0      |      24      | multiple cpus are guaranteed to
>>             |              | be monotonic
>> -------------------------------------------------------------
>>             |              | guest vcpu has been paused by
>>      1      |     N/A      | the host
>>             |              |
>> -------------------------------------------------------------
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> 
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Thanks!

>> ---
>>  xen/include/public/xen.h | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
>> index ff5547e..1223686 100644
>> --- a/xen/include/public/xen.h
>> +++ b/xen/include/public/xen.h
>> @@ -601,10 +601,14 @@ struct vcpu_time_info {
>>       */
>>      uint32_t tsc_to_system_mul;
>>      int8_t   tsc_shift;
>> -    int8_t   pad1[3];
>> +    int8_t   flags;
>> +    int8_t   pad1[2];
>>  }; /* 32 bytes */
>>  typedef struct vcpu_time_info vcpu_time_info_t;
>>  
>> +#define PVCLOCK_TSC_STABLE_BIT	(1 << 0)
>> +#define PVCLOCK_GUEST_STOPPED	(1 << 1)
>> +
>>  struct vcpu_info {
>>      /*
>>       * 'evtchn_upcall_pending' is written non-zero by Xen to indicate
>> -- 
>> 2.1.4
>>
>>
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