Re: [Xen-devel] [RFC PATCH 58/84] x86/mm: fix leaks in map_xen_pagetable.

[<hongyax@xxxxxxxxxx>]

On 26/09/2019 14:16, Wei Liu wrote:
> On Thu, Sep 26, 2019 at 10:46:21AM +0100, hongyax@xxxxxxxxxx wrote:
> > diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> > index b2b2edbed1..145c5ab47c 100644
> > --- a/xen/arch/x86/mm.c
> > +++ b/xen/arch/x86/mm.c
> > @@ -5160,6 +5160,7 @@ int map_pages_to_xen(
> >                                !(l2e_get_flags(ol2e) & _PAGE_PSE) )
> >                               free_xen_pagetable(l2e_get_mfn(ol2e));
> >                       }
> > +                    UNMAP_XEN_PAGETABLE(l2t);
> This is presumably the issue you try to fix.
Yes. Actually this patch fixes two issues, this is the first one.

> > diff --git a/xen/common/vmap.c b/xen/common/vmap.c
> > index faebc1ddf1..fcdb8495c8 100644
> > --- a/xen/common/vmap.c
> > +++ b/xen/common/vmap.c
> I fail to see why you need to change vmap to fix a leak somewhere else.
The second leak is that after the patches, we cannot just call vmap_to_mfn() 
because it calls virt_to_xen_l1e() under the hood which maps a page. We have to 
unmap it, therefore I modified the vmap_to_mfn to also do the unmapping. This 
is a separate issue than the first one, so maybe I could split the patch into two.
> I guess I will need to wait for your branch to have a closer look.
>
> Wei.

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