RE: [PATCH 03/10] viridian: introduce a per-cpu hypercall_vpmask and accessor functions...

["Durrant, Paul" <pdurrant@amazon.co.uk>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: 19 November 2020 16:41
> To: paul@xen.org
> Cc: Durrant, Paul <pdurrant@amazon.co.uk>; 'Wei Liu' <wl@xen.org>; 'Andrew Cooper'
> <andrew.cooper3@citrix.com>; 'Roger Pau Monné' <roger.pau@citrix.com>; xen-devel@lists.xenproject.org
> Subject: RE: [EXTERNAL] [PATCH 03/10] viridian: introduce a per-cpu hypercall_vpmask and accessor
> functions...
> 
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> 
> On 19.11.2020 17:02, Paul Durrant wrote:
> >> From: Jan Beulich <jbeulich@suse.com
> >> Sent: 12 November 2020 08:46
> >>
> >> On 11.11.2020 21:07, Paul Durrant wrote:
> >>> --- a/xen/arch/x86/hvm/viridian/viridian.c
> >>> +++ b/xen/arch/x86/hvm/viridian/viridian.c
> >>> @@ -507,15 +507,41 @@ void viridian_domain_deinit(struct domain *d)
> >>>      XFREE(d->arch.hvm.viridian);
> >>>  }
> >>>
> >>> +struct hypercall_vpmask {
> >>> +    DECLARE_BITMAP(mask, HVM_MAX_VCPUS);
> >>> +};
> >>> +
> >>> +static DEFINE_PER_CPU(struct hypercall_vpmask, hypercall_vpmask);
> >>> +
> >>> +static void vpmask_empty(struct hypercall_vpmask *vpmask)
> >>
> >> const?
> >
> > Yes, I suppose that's ook for all these since the outer struct is
> > not changing... It's a bit misleading though.
> 
> I'd be curious to learn about that "misleading" aspect.
> 

Because the function is modifying (zero-ing) the bitmap... so implying the mask is const is measleading.

  Paul

> Jan