[PATCH] libxc: correct memory range check in domain builder

[PATCH] libxc: correct memory range check in domain builder

[Juergen Gross]

Commit 81a76e4b12961a9f54f5021809074196dfe6dbba ("libxc: rework of
domain builder's page table handler") introduced a regression with
checking the required memory size of the domain. The needed maximum pfn
of the initial kernel mapping was added to the currently last used pfn
resulting in doubling the estimated memory need.

Correct the calculation of the last needed pfn to enable booting of
small domains again.

Reported-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 tools/libxc/xc_dom_x86.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index 2a3f64b..ac4dae5 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -164,7 +164,7 @@ static int count_pgtables(struct xc_dom_image *dom, xen_vaddr_t from,
 
     for ( l = domx86->params->levels - 1; l >= 0; l-- )
     {
-        map->lvls[l].pfn = pfn + map->area.pgtables;
+        map->lvls[l].pfn = dom->pfn_alloc_end + map->area.pgtables;
         if ( l == domx86->params->levels - 1 )
         {
             /* Top level page table in first mapping only. */
@@ -238,8 +238,7 @@ static int alloc_pgtables(struct xc_dom_image *dom)
         try_virt_end = round_up(dom->virt_alloc_end + pages * PAGE_SIZE_X86,
                                 bits_to_mask(22)); /* 4MB alignment */
 
-        if ( count_pgtables(dom, dom->parms.virt_base, try_virt_end,
-                            dom->pfn_alloc_end) )
+        if ( count_pgtables(dom, dom->parms.virt_base, try_virt_end, 0) )
             return -1;
 
         pages = map->area.pgtables + extra_pages;
-- 
2.6.2

Re: [PATCH] libxc: correct memory range check in domain builder

[Anthony PERARD]

On Mon, Feb 08, 2016 at 03:23:52PM +0100, Juergen Gross wrote:
> Commit 81a76e4b12961a9f54f5021809074196dfe6dbba ("libxc: rework of
> domain builder's page table handler") introduced a regression with
> checking the required memory size of the domain. The needed maximum pfn
> of the initial kernel mapping was added to the currently last used pfn
> resulting in doubling the estimated memory need.
> 
> Correct the calculation of the last needed pfn to enable booting of
> small domains again.
> 
> Reported-by: Anthony Perard <anthony.perard@citrix.com>
> Signed-off-by: Juergen Gross <jgross@suse.com>

It works for me, using xl. I have not try with the full stack
(openstack/libvirt), but I expect it to work.

Tested-by: Anthony PERARD <anthony.perard@citrix.com>

Thanks,

-- 
Anthony PERARD

Re: [PATCH] libxc: correct memory range check in domain builder

[Ian Campbell]

On Mon, 2016-02-08 at 15:20 +0000, Anthony PERARD wrote:
> On Mon, Feb 08, 2016 at 03:23:52PM +0100, Juergen Gross wrote:
> > Commit 81a76e4b12961a9f54f5021809074196dfe6dbba ("libxc: rework of
> > domain builder's page table handler") introduced a regression with
> > checking the required memory size of the domain. The needed maximum pfn
> > of the initial kernel mapping was added to the currently last used pfn
> > resulting in doubling the estimated memory need.
> > 
> > Correct the calculation of the last needed pfn to enable booting of
> > small domains again.
> > 
> > Reported-by: Anthony Perard <anthony.perard@citrix.com>
> > Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> It works for me, using xl. I have not try with the full stack
> (openstack/libvirt), but I expect it to work.
> 
> Tested-by: Anthony PERARD <anthony.perard@citrix.com>

thanks, acked + applied.