Re: [Xen-devel] [PATCH v4 06/10] hvm/hpet: In hpet_save, call hpet_get_comparator.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.05.14 at 22:18, <dslutz@xxxxxxxxxxx> wrote:
> This changes save data to consistent/expected values.  It is not
> technically required because hpet_get_comparator() will adjust from
> any value to the correct value. And hpet_get_comparator() is
> effectivly called in hpet_load via hpet_set_timer.
> 
> However it does look strange to people that the output from
> xen-hvmctx for the comparator values do not change when the master
> clock does.
> 
> The software-developers-hpet-spec-1-0a.pdf says that the comparator
> will allways be greater than master clock for a periodic timer.
> 
> Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

> ---
> v4:
>   Correctly set guest_time.
>   Fix formatting of comments.
> 
>  xen/arch/x86/hvm/hpet.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/hpet.c b/xen/arch/x86/hvm/hpet.c
> index 0789947..b611304 100644
> --- a/xen/arch/x86/hvm/hpet.c
> +++ b/xen/arch/x86/hvm/hpet.c
> @@ -495,12 +495,14 @@ static int hpet_save(struct domain *d, 
> hvm_domain_context_t *h)
>  {
>      HPETState *hp = domain_vhpet(d);
>      int rc;
> +    uint64_t guest_time;
>  
>      spin_lock(&hp->lock);
> +    guest_time = guest_time_hpet(hp);
>  
>      /* Write the proper value into the main counter */
>      if ( hpet_enabled(hp) )
> -        hp->hpet.mc64 = hp->mc_offset + guest_time_hpet(hp);
> +        hp->hpet.mc64 = hp->mc_offset + guest_time;
>  
>      /* Save the HPET registers */
>      rc = _hvm_init_entry(h, HVM_SAVE_CODE(HPET), 0, HVM_SAVE_LENGTH(HPET));
> @@ -524,8 +526,18 @@ static int hpet_save(struct domain *d, 
> hvm_domain_context_t *h)
>          C(period[1]);
>          C(period[2]);
>  #undef C
> -        /* save the 64 bit comparator in the 64 bit timer[n].cmp field
> -         * regardless of whether or not the timer is in 32 bit mode. */
> +        /*
> +         * read the comparator to get it updated so hpet_save will
> +         * return the expected value.
> +         */
> +        hpet_get_comparator(hp, 0, guest_time);
> +        hpet_get_comparator(hp, 1, guest_time);
> +        hpet_get_comparator(hp, 2, guest_time);
> +        /*
> +         * save the 64 bit comparator in the 64 bit timer[n].cmp
> +         * field regardless of whether or not the timer is in 32 bit
> +         * mode.
> +         */
>          rec->timers[0].cmp = hp->hpet.comparator64[0];
>          rec->timers[1].cmp = hp->hpet.comparator64[1];
>          rec->timers[2].cmp = hp->hpet.comparator64[2];
> -- 
> 1.8.4




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