Re: [Xen-devel] [PATCH 08/14] xen: balloon: allow PVMMU interfaces to be compiled out

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-10-05 at 14:19 +0100, Stefano Stabellini wrote:
> On Thu, 4 Oct 2012, Ian Campbell wrote:
> > The ARM platform has no concept of PVMMU and therefor no
> > HYPERVISOR_update_va_mapping et al. Allow this code to be compiled out
> > when not required.
> > 
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> 
> I am unsure whether it is worth a new symbol and two ifdef's

ARM doesn't compile without it, since HYPERVISOR_update_va_mapping
doesn't exist. Do you have a preferable alternative?

I'm not sure how much more of this sort of thing there will be as we
enable more features on the ARM port.

> 
> 
> >  arch/x86/xen/Kconfig  |    1 +
> >  drivers/xen/Kconfig   |    3 +++
> >  drivers/xen/balloon.c |    4 ++++
> >  3 files changed, 8 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
> > index fdce49c..c31ee77 100644
> > --- a/arch/x86/xen/Kconfig
> > +++ b/arch/x86/xen/Kconfig
> > @@ -6,6 +6,7 @@ config XEN
> >     bool "Xen guest support"
> >     select PARAVIRT
> >     select PARAVIRT_CLOCK
> > +   select XEN_HAVE_PVMMU
> >     depends on X86_64 || (X86_32 && X86_PAE && !X86_VISWS)
> >     depends on X86_CMPXCHG && X86_TSC
> >     help
> > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> > index d4dffcd..9c00652 100644
> > --- a/drivers/xen/Kconfig
> > +++ b/drivers/xen/Kconfig
> > @@ -204,4 +204,7 @@ config XEN_MCE_LOG
> >       Allow kernel fetching MCE error from Xen platform and
> >       converting it into Linux mcelog format for mcelog tools
> >  
> > +config XEN_HAVE_PVMMU
> > +       bool
> > +
> >  endmenu
> > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> > index 1b56ae0..cfe47dae 100644
> > --- a/drivers/xen/balloon.c
> > +++ b/drivers/xen/balloon.c
> > @@ -360,6 +360,7 @@ static enum bp_state increase_reservation(unsigned long 
> > nr_pages)
> >             if (!xen_feature(XENFEAT_auto_translated_physmap))
> >                     set_phys_to_machine(pfn, frame_list[i]);
> >  
> > +#ifdef CONFIG_XEN_HAVE_PVMMU
> >             /* Link back into the page tables if not highmem. */
> >             if (xen_pv_domain() && !PageHighMem(page) && 
> >                 !xen_feature(XENFEAT_auto_translated_physmap)) {
> > @@ -371,6 +372,7 @@ static enum bp_state increase_reservation(unsigned long 
> > nr_pages)
> >                             0);
> >                     BUG_ON(ret);
> >             }
> > +#endif
> >  
> >             /* Relinquish the page back to the allocator. */
> >             ClearPageReserved(page);
> > @@ -419,6 +421,7 @@ static enum bp_state decrease_reservation(unsigned long 
> > nr_pages, gfp_t gfp)
> >  
> >             scrub_page(page);
> >  
> > +#ifdef CONFIG_XEN_HAVE_PVMMU
> >             if (xen_pv_domain() && !PageHighMem(page) &&
> >                 !xen_feature(XENFEAT_auto_translated_physmap)) {
> >                             ret = HYPERVISOR_update_va_mapping(
> > @@ -426,6 +429,7 @@ static enum bp_state decrease_reservation(unsigned long 
> > nr_pages, gfp_t gfp)
> >                                     __pte_ma(0), 0);
> >                             BUG_ON(ret);
> >             }
> > +#endif
> >     }
> >  
> >     /* Ensure that ballooned highmem pages don't have kmaps. */
> > -- 
> > 1.7.2.5
> > 



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