Re: [Xen-devel] [PATCH V10 05/14] xen/pvh: balloon and grant changes.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 13 Dec 2013, Konrad Rzeszutek Wilk wrote:
> On Fri, Dec 13, 2013 at 11:56:31AM +0000, Stefano Stabellini wrote:
> > On Thu, 12 Dec 2013, Konrad Rzeszutek Wilk wrote:
> > > From: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> > > 
> > > For balloon changes we skip setting of local P2M as it's updated
> > > in Xen. For grant, the shared grant frame is the PFN and not MFN,
> > > hence its mapped via the same code path as HVM.
> > > 
> > > Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> > > [v1: Rebase on v3.7-rc3]
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > > CC: <stefano.stabellini@xxxxxxxxxxxxx>
> > > Conflicts:
> > >   drivers/xen/balloon.c
> > > [v2: Rebase on v3.13-rc3 has lot of ARM changes.]
> > > ---
> > >  drivers/xen/balloon.c     |   37 ++++++++++++++++++++-----------------
> > >  drivers/xen/gntdev.c      |    3 ++-
> > >  drivers/xen/grant-table.c |   25 ++++++++++++++++++++++---
> > >  3 files changed, 44 insertions(+), 21 deletions(-)
> > > 
> > > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> > > index 55ea73f..0e9875a 100644
> > > --- a/drivers/xen/balloon.c
> > > +++ b/drivers/xen/balloon.c
> > > @@ -354,7 +354,9 @@ static enum bp_state increase_reservation(unsigned 
> > > long nr_pages)
> > >  
> > >  #ifdef CONFIG_XEN_HAVE_PVMMU
> > >           /* Link back into the page tables if not highmem. */
> > > -         if (xen_pv_domain() && !PageHighMem(page)) {
> > > +         if (xen_pv_domain() && !PageHighMem(page) &&
> > > +             !xen_feature(XENFEAT_auto_translated_physmap)) {
> > > +
> > >                   int ret;
> > >                   ret = HYPERVISOR_update_va_mapping(
> > >                           (unsigned long)__va(pfn << PAGE_SHIFT),
> > > @@ -411,28 +413,29 @@ static enum bp_state decrease_reservation(unsigned 
> > > long nr_pages, gfp_t gfp)
> > >  
> > >           scrub_page(page);
> > >  
> > > -         /*
> > > -          * Ballooned out frames are effectively replaced with
> > > -          * a scratch frame.  Ensure direct mappings and the
> > > -          * p2m are consistent.
> > > -          */
> > > -         scratch_page = get_balloon_scratch_page();
> > > +         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> > > +                 unsigned long p;
> > > +
> > > +                 /*
> > > +                  * Ballooned out frames are effectively replaced with
> > > +                  * a scratch frame.  Ensure direct mappings and the
> > > +                  * p2m are consistent.
> > > +                  */
> > > +                 scratch_page = get_balloon_scratch_page();
> > >  #ifdef CONFIG_XEN_HAVE_PVMMU
> > > -         if (xen_pv_domain() && !PageHighMem(page)) {
> > > -                 ret = HYPERVISOR_update_va_mapping(
> > > -                         (unsigned long)__va(pfn << PAGE_SHIFT),
> > > -                         pfn_pte(page_to_pfn(scratch_page),
> > > +                 if (xen_pv_domain() && !PageHighMem(page)) {
> > > +                         ret = HYPERVISOR_update_va_mapping(
> > > +                                 (unsigned long)__va(pfn << PAGE_SHIFT),
> > > +                                 pfn_pte(page_to_pfn(scratch_page),
> > >                                   PAGE_KERNEL_RO), 0);
> > > -                 BUG_ON(ret);
> > > -         }
> > > +                         BUG_ON(ret);
> > > +                 }
> > >  #endif
> > > -         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> > > -                 unsigned long p;
> > >                   p = page_to_pfn(scratch_page);
> > >                   __set_phys_to_machine(pfn, pfn_to_mfn(p));
> > > -         }
> > > -         put_balloon_scratch_page();
> > >  
> > > +                 put_balloon_scratch_page();
> > > +         }
> > >           balloon_append(pfn_to_page(pfn));
> > >   }
> > 
> > These changes to balloon.c are similar to my patch but:
> > 
> > - they don't prevent set_phys_to_machine from being called by
> > increase_reservation for auto_translated guests
> 
> <nods>
> > 
> > - they don't prevent wasteful balloon_scratch_page from being allocated
> > for auto_translated guests
> 
> <nods>
> > 
> > I think that it would be best to take my patch instead.
> 
> Lets focus the review on your patch then and have it part of this
> series. 

OK, but keep in mind that Xen on ARMv8 is currently broken without that
patch.

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