Re: [Xen-devel] [PATCH v2 03/10] xen: extend XEN_DOMCTL_memory_mapping to handle memory policy

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 18 Jun 2019, Stefano Stabellini wrote:
> On Tue, 18 Jun 2019, Jan Beulich wrote:
> > >>> On 17.06.19 at 23:28, <sstabellini@xxxxxxxxxx> wrote:
> > > On Thu, 2 May 2019, Jan Beulich wrote:
> > >> >>> On 30.04.19 at 23:02, <sstabellini@xxxxxxxxxx> wrote:
> > >> > --- a/xen/include/public/domctl.h
> > >> > +++ b/xen/include/public/domctl.h
> > >> > @@ -571,12 +571,24 @@ struct xen_domctl_bind_pt_irq {
> > >> >  */
> > >> >  #define DPCI_ADD_MAPPING         1
> > >> >  #define DPCI_REMOVE_MAPPING      0
> > >> > +/*
> > >> > + * Default memory policy. Corresponds to:
> > >> > + * Arm: MEMORY_POLICY_ARM_DEV_nGRE
> > >> > + * x86: MEMORY_POLICY_X86_UC
> > >> > + */
> > >> > +#define MEMORY_POLICY_DEFAULT    0
> > >> > +/* x86 only. Memory type UNCACHABLE */
> > >> > +#define MEMORY_POLICY_X86_UC     0
> > >> 
> > >> I'm afraid this may end up misleading, as on NPT and in
> > >> shadow mode we use UC- instead of UC afaics. Andrew,
> > >> do you have an opinion either way what exactly should
> > >> be stated here?
> > > 
> > > Ping?
> > 
> > To me? I've stated my opinion.
> 
> I cannot name the macro "MEMORY_POLICY_X86_UC-" because it cannot end
> with a "-". Instead, I can name it MEMORY_POLICY_X86_UC_MINUS that seems
> to be what Linux does. I'll rename the optional xl parameter too from
> "x86_uc" to "x86_uc_minus".

I chatted with Andrew on IRC and he suggested to get rid of the option
entirely -- there is just one on x86 and doesn't necessarily need to be
explicitly visible. We could only have MEMORY_POLICY_DEFAULT, and also
remove the x86_uc setting from libxl/xl.

I am OK with this. However, given that I have already made all the
changes to have MEMORY_POLICY_X86_UC_MINUS and x86_uc_minus everywhere,
I'll send an update of the series with them.

Then you can decide whether you want to keep things like that or get rid
of it. Of course removing code is easy -- I am always happy to do it if
that's what you want.

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