[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1 of 6] The PoD code may split a 1GB superpage in a potentially unlocked way
(Including xen-devel in my reply...) On Mon, Nov 14, 2011 at 9:48 PM, Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx> wrote: > xen/arch/x86/mm/p2m-pod.c | 1 - > xen/arch/x86/mm/p2m-pt.c | 9 ++++++--- > 2 files changed, 6 insertions(+), 4 deletions(-) > > > The path p2m-lookup -> p2m-pt->get_entry -> 1GB PoD superpage -> > pod_demand_populate ends in the pod code performing a p2m_set_entry with > no locks held (in order to split the 1GB superpage into 512 2MB ones) > > Further, it calls p2m_unlock after that, which will break the spinlock. Yeah, not sure how this got to be the way it did... good catch. Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx> > > This patch attempts to fix that. > > Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx> > > diff -r 0844b17df7a9 -r d9a344a5c1e3 xen/arch/x86/mm/p2m-pod.c > --- a/xen/arch/x86/mm/p2m-pod.c > +++ b/xen/arch/x86/mm/p2m-pod.c > @@ -987,7 +987,6 @@ p2m_pod_demand_populate(struct p2m_domai > set_p2m_entry(p2m, gfn_aligned, _mfn(0), PAGE_ORDER_2M, > p2m_populate_on_demand, p2m->default_access); > audit_p2m(p2m, 1); > - p2m_unlock(p2m); > return 0; > } > > diff -r 0844b17df7a9 -r d9a344a5c1e3 xen/arch/x86/mm/p2m-pt.c > --- a/xen/arch/x86/mm/p2m-pt.c > +++ b/xen/arch/x86/mm/p2m-pt.c > @@ -542,10 +542,11 @@ pod_retry_l3: > /* The read has succeeded, so we know that mapping exists */ > if ( q != p2m_query ) > { > - if ( !p2m_pod_demand_populate(p2m, gfn, PAGE_ORDER_1G, q) ) > + if ( !p2m_pod_check_and_populate(p2m, gfn, > + (l1_pgentry_t *) &l3e, PAGE_ORDER_1G, > q) ) > goto pod_retry_l3; > p2mt = p2m_invalid; > - printk("%s: Allocate 1GB failed!\n", __func__); > + gdprintk(XENLOG_ERR, "%s: Allocate 1GB failed!\n", __func__); > goto out; > } > else > @@ -743,8 +744,10 @@ pod_retry_l3: > { > if ( q != p2m_query ) > { > - if ( !p2m_pod_demand_populate(p2m, gfn, PAGE_ORDER_1G, > q) ) > + if ( !p2m_pod_check_and_populate(p2m, gfn, > + (l1_pgentry_t *) l3e, PAGE_ORDER_1G, > q) ) > goto pod_retry_l3; > + gdprintk(XENLOG_ERR, "%s: Allocate 1GB failed!\n", > __func__); > } > else > *t = p2m_populate_on_demand; > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxxxxxxxx > http://lists.xensource.com/xen-devel > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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