Re: [PATCH] xen/privcmd: Support correctly 64KB page granularity when mapping memory

[Julien Grall]

Hi Boris,

On 31/05/17 14:54, Boris Ostrovsky wrote:
> On 05/31/2017 09:03 AM, Julien Grall wrote:
> > Commit 5995a68 "xen/privcmd: Add support for Linux 64KB page granularity" did
> > not go far enough to support 64KB in mmap_batch_fn.
> >
> > The variable 'nr' is the number of 4KB chunk to map. However, when Linux
> > is using 64KB page granularity the array of pages (vma->vm_private_data)
> > contain one page per 64KB. Fix it by incrementing st->index correctly.
> >
> > Furthermore, st->va is not correctly incremented as PAGE_SIZE !=
> > XEN_PAGE_SIZE.
> >
> > Fixes: 5995a68 ("xen/privcmd: Add support for Linux 64KB page granularity")
> > CC: stable@xxxxxxxxxxxxxxx
> > Reported-by: Feng Kan <fkan@xxxxxxx>
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> > ---
> >  drivers/xen/privcmd.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> > index 7a92a5e1d40c..feca75b07fdd 100644
> > --- a/drivers/xen/privcmd.c
> > +++ b/drivers/xen/privcmd.c
> > @@ -362,8 +362,8 @@ static int mmap_batch_fn(void *data, int nr, void *state)
> >  				st->global_error = 1;
> >  		}
> >  	}
> > -	st->va += PAGE_SIZE * nr;
> > -	st->index += nr;
> > +	st->va += XEN_PAGE_SIZE * nr;
> > +	st->index += nr / XEN_PFN_PER_PAGE;
> >
> >  	return 0;
> >  }
>
>
> Are we still using PAGE_MASK for xen_remap_domain_gfn_array()?

Do you mean in the xen_xlate_remap_gfn_array implementation? If so there 
are no use of PAGE_MASK as the code has been converted to support 64K 
page granularity.

If you mean the x86 version of xen_remap_domain_gfn_array, then we don't 
really care as x86 only use 4KB page granularity.

Cheers,

--
Julien Grall