Re: [Xen-devel] [PATCH V3 4/8] xen: Delay invalidating extra memory

[Juergen Gross <jgross@xxxxxxxx>]

On 11/12/2014 11:10 PM, Konrad Rzeszutek Wilk wrote:
> > @@ -376,12 +374,14 @@ void __init xen_build_dynamic_phys_to_machine(void)
> >         unsigned long max_pfn;
> >         unsigned long pfn;
> >
> > -        if (xen_feature(XENFEAT_auto_translated_physmap))
> > +       if (xen_feature(XENFEAT_auto_translated_physmap))
> Spurious change.
I'll remove it.

> .. snip..
> > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> > index 0e5f9b6..8d5985b 100644
> > --- a/arch/x86/xen/setup.c
> > +++ b/arch/x86/xen/setup.c
> > @@ -75,7 +75,6 @@ static unsigned long xen_remap_mfn __initdata = 
> > INVALID_P2M_ENTRY;
> >
> >   static void __init xen_add_extra_mem(u64 start, u64 size)
> >   {
> > -       unsigned long pfn;
> >         int i;
> >
> >         for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
> > @@ -95,17 +94,74 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
> >                 printk(KERN_WARNING "Warning: not enough extra memory 
> > regions\n");
> >
> >         memblock_reserve(start, size);
> > +}
> >
> > -       xen_max_p2m_pfn = PFN_DOWN(start + size);
> > -       for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn; pfn++) {
> > -               unsigned long mfn = pfn_to_mfn(pfn);
> > +static void __init xen_del_extra_mem(u64 start, u64 size)
> > +{
> > +       int i;
> > +       u64 start_r, size_r;
> >
> > -               if (WARN_ONCE(mfn == pfn, "Trying to over-write 1-1 mapping (pfn: 
> > %lx)\n", pfn))
> > -                       continue;
> > -               WARN_ONCE(mfn != INVALID_P2M_ENTRY, "Trying to remove %lx which has 
> > %lx mfn!\n",
> > -                         pfn, mfn);
> > +       for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
> > +               start_r = xen_extra_mem[i].start;
> > +               size_r = xen_extra_mem[i].size;
> > +
> > +               /* Start of region. */
> > +               if (start_r == start) {
> > +                       BUG_ON(size > size_r);
> > +                       xen_extra_mem[i].start += size;
> > +                       xen_extra_mem[i].size -= size;
> > +                       break;
> > +               }
> > +               /* End of region. */
> > +               if (start_r + size_r == start + size) {
> > +                       BUG_ON(size > size_r);
> > +                       xen_extra_mem[i].size -= size;
> > +                       break;
> > +               }
> > +               /* Mid of region. */
> > +               if (start > start_r && start < start_r + size_r) {
> > +                       BUG_ON(start + size > start_r + size_r);
> > +                       xen_extra_mem[i].size = start - start_r;
> > +                       xen_add_extra_mem(start + size, start_r + size_r -
> > +                                         (start + size));
> Which ends up calling 'memblock_reserve' for an region it already has
> reserved. Should we call memblock_free(start_r, size_r - size) before calling 
> this?
>
> Or is that not neccessary as memblock_* is pretty smart about this sort of 
> thing?
Regions marked via memblock_reserve() are allowed to overlap. I can add
a comment.


Juergen


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