Re: [Xen-devel] [PATCH v3 4/5] x86/PV: allow PV guests to have an emulated PIT

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.01.16 at 12:57, <roger.pau@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -542,8 +542,11 @@ int arch_domain_create(struct domain *d, unsigned int 
> domcr_flags,
>                     d->domain_id, config->emulation_flags);
>              return -EINVAL;
>          }
> -        if ( config->emulation_flags != 0 &&
> -             (!is_hvm_domain(d) || config->emulation_flags != 
> XEN_X86_EMU_ALL) )
> +        if ( is_hardware_domain(d) )
> +            config->emulation_flags |= XEN_X86_EMU_PIT;
> +        if ( !is_hvm_domain(d) ? (config->emulation_flags != 
> XEN_X86_EMU_PIT) :
> +                                 (config->emulation_flags != XEN_X86_EMU_ALL 
> &&
> +                                  config->emulation_flags != 0))
>          {
>              printk(XENLOG_G_ERR "d%d: Xen does not allow %s domain creation "
>                     "with the current selection of emulators: %#x\n",

While you mentioned in the cover letter that this needs to be
committed together with patch 5, having them as separate
commits would still break bisectabaility afaict. Would it really
be so unreasonable to allow PV(H) DomU-s to not have an
emulated PIT, depending on (a future) tool stack gathered
per-domain setting? Converting the check above accordingly
would - afaict - at once break that dependency on patch 5.

Jan


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