Re: [Xen-devel] [PATCH] xen/arm: mm: optimize setup_pagetables

[Julien Grall <julien.grall@xxxxxxx>]

On 11/05/2016 10:57, Peng Fan wrote:
> Hi Julien,
Hi Peng,

> On Wed, May 11, 2016 at 10:31:49AM +0100, Julien Grall wrote:
> > [...]
> >
> > > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> > > index 94ea054..bebd82f 100644
> > > --- a/xen/arch/arm/mm.c
> > > +++ b/xen/arch/arm/mm.c
> > > @@ -443,12 +443,6 @@ void __init setup_pagetables(unsigned long 
> > > boot_phys_offset, paddr_t xen_paddr)
> > >       lpae_t pte, *p;
> > >       int i;
> > >
> > > -    /* Map the destination in the boot misc area. */
> > > -    dest_va = BOOT_RELOC_VIRT_START;
> > > -    pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
> > > -    write_pte(xen_second + second_table_offset(dest_va), pte);
> > > -    flush_xen_data_tlb_range_va_local(dest_va, SECOND_SIZE);
> > > -
> > >       /* Calculate virt-to-phys offset for the new location */
> > >       phys_offset = xen_paddr - (unsigned long) _start;
> > >
> > > @@ -498,6 +492,11 @@ void __init setup_pagetables(unsigned long 
> > > boot_phys_offset, paddr_t xen_paddr)
> > >       /* Map the destination in the boot misc area. */
> > >       dest_va = BOOT_RELOC_VIRT_START;
> > >       pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
> > > +    xen_second[second_table_offset(dest_va)] = pte;
> > > +
> > > +    /* Map the destination in the boot misc area. */
> > > +    dest_va = BOOT_RELOC_VIRT_START;
> > > +    pte = mfn_to_xen_entry(xen_paddr >> PAGE_SHIFT, WRITEALLOC);
> > Why do you need to recompute "pte" and "dest_va"? They will be the same for
> > "boot_second" and "xen_second".
> I just change "write_pte(xen_second + second_table_offset(dest_va), pte);" to
> "xen_second[second_table_offset(dest_va)] = pte;".
>
> The pte and dest_va are not changed.
So you could do some like:

/* Comment */
dest_va = BOOT...
pte = ...
/* Comment */
xen_second[...] = pte
/* Comment */
write_pte(boot_second...);

Regards,

--
Julien Grall

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