Re: [Xen-devel] [PATCH 3/9] x86: enclose hypercall page initialisation code in CONFIG_{HVM, PV}

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.08.18 at 18:08, <wei.liu2@xxxxxxxxxx> wrote:
> On Tue, Aug 07, 2018 at 04:44:13AM -0600, Jan Beulich wrote:
>> >>> On 07.08.18 at 12:00, <wei.liu2@xxxxxxxxxx> wrote:
>> > --- a/xen/arch/x86/x86_64/traps.c
>> > +++ b/xen/arch/x86/x86_64/traps.c
>> > @@ -352,12 +352,19 @@ void subarch_percpu_traps_init(void)
>> >  void hypercall_page_initialise(struct domain *d, void *hypercall_page)
>> >  {
>> >      memset(hypercall_page, 0xCC, PAGE_SIZE);
>> > +#if CONFIG_HVM
>> >      if ( is_hvm_domain(d) )
>> >          hvm_hypercall_page_initialise(d, hypercall_page);
>> > -    else if ( !is_pv_32bit_domain(d) )
>> > -        hypercall_page_initialise_ring3_kernel(hypercall_page);
>> > -    else
>> > -        hypercall_page_initialise_ring1_kernel(hypercall_page);
>> > +#endif
>> > +#if CONFIG_PV
>> > +    if ( is_pv_domain(d) )
>> > +    {
>> > +        if ( !is_pv_32bit_domain(d) )
>> > +            hypercall_page_initialise_ring3_kernel(hypercall_page);
>> > +        else
>> > +            hypercall_page_initialise_ring1_kernel(hypercall_page);
>> > +    }
>> > +#endif
>> >  }
>> 
>> I'm not convinced: This is uglier to read, and things like is_hvm_domain()
>> should evaluate to constant false anyway without the respective
>> CONFIG_* setting enabled.
> 
> I take it you are against adding CONFIG_* here?
> 
> The addition of is_pv_domain branch is still needed because both sets
> might get compiled out.

But that can be done by making the sequence

        if ( is_hvm_... )
        else if ( is_pv_32bit_... )
        else if ( is_pv_... )

I.e. in particular without any changes to the nesting.

Jan



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