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

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

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
> 
> 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>
> ---
>  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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