Re: [Xen-devel] [PATCH v2 1/6] public/xen.h: add flags field to vcpu_time_info

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.03.16 at 15:44, <joao.m.martins@xxxxxxxxxx> wrote:
> This field has two possible flags (as of latest pvclock ABI
> shared with KVM).
> 
> 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@xxxxxxxxxx>

With one further adjustment (which could be done while committing)
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -614,10 +614,14 @@ struct vcpu_time_info {
>       */
>      uint32_t tsc_to_system_mul;
>      int8_t   tsc_shift;
> -    int8_t   pad1[3];
> +    uint8_t  flags;
> +    uint8_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)

No new identifiers not properly prefixed by XEN_ (or, elsewhere,
xen_) in the canonical public headers please (whether
downstream consumers like Linux elect to strip such prefixes is
an independent aspect).

Jan


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