Re: [Xen-devel] [PATCH v3 1/3] xen/arm: implement steal_page

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 8 Aug 2013, Ian Campbell wrote:
> On Mon, 2013-08-05 at 17:40 +0100, Stefano Stabellini wrote:
> 
> Isn't this identical to the x86 version? Can we make that common
> instead?

Yes, it is identical. I can move it to common/memory.c.


> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > ---
> >  xen/arch/arm/mm.c |   43 +++++++++++++++++++++++++++++++++++++++++++
> >  1 files changed, 43 insertions(+), 0 deletions(-)
> > 
> > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> > index f301e65..ea64c03 100644
> > --- a/xen/arch/arm/mm.c
> > +++ b/xen/arch/arm/mm.c
> > @@ -751,6 +751,49 @@ int donate_page(struct domain *d, struct page_info 
> > *page, unsigned int memflags)
> >  int steal_page(
> >      struct domain *d, struct page_info *page, unsigned int memflags)
> >  {
> > +    unsigned long x, y;
> > +    bool_t drop_dom_ref = 0;
> > +
> > +    spin_lock(&d->page_alloc_lock);
> > +
> > +    if ( is_xen_heap_page(page) || (page_get_owner(page) != d) )
> > +        goto fail;
> > +
> > +    /*
> > +     * We require there is just one reference (PGC_allocated). We 
> > temporarily
> > +     * drop this reference now so that we can safely swizzle the owner.
> > +     */
> > +    y = page->count_info;
> > +    do {
> > +        x = y;
> > +        if ( (x & (PGC_count_mask|PGC_allocated)) != (1 | PGC_allocated) )
> > +            goto fail;
> > +        y = cmpxchg(&page->count_info, x, x & ~PGC_count_mask);
> > +    } while ( y != x );
> > +
> > +    /* Swizzle the owner then reinstate the PGC_allocated reference. */
> > +    page_set_owner(page, NULL);
> > +    y = page->count_info;
> > +    do {
> > +        x = y;
> > +        BUG_ON((x & (PGC_count_mask|PGC_allocated)) != PGC_allocated);
> > +    } while ( (y = cmpxchg(&page->count_info, x, x | 1)) != x );
> > +
> > +    /* Unlink from original owner. */
> > +    if ( !(memflags & MEMF_no_refcount) && !domain_adjust_tot_pages(d, -1) 
> > )
> > +        drop_dom_ref = 1;
> > +    page_list_del(page, &d->page_list);
> > +
> > +    spin_unlock(&d->page_alloc_lock);
> > +    if ( unlikely(drop_dom_ref) )
> > +        put_domain(d);
> > +    return 0;
> > +
> > + fail:
> > +    spin_unlock(&d->page_alloc_lock);
> > +    printk("Bad page %p: ed=%p(%u), sd=%p, caf=%08lx, taf=%lx\n",
> > +            (void *)page_to_mfn(page), d, d->domain_id,
> > +            page_get_owner(page), page->count_info, 
> > page->u.inuse.type_info);
> >      return -1;
> >  }
> >  
> 
> 

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