[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RESEND] nested EPT: fix the handling of nested EPT.
> -----Original Message----- > From: Tim Deegan [mailto:tim@xxxxxxx] > Sent: Thursday, June 04, 2015 9:11 PM > To: Li, Liang Z > Cc: xen-devel@xxxxxxxxxxxxx; keir@xxxxxxx; jbeulich@xxxxxxxx; > andrew.cooper3@xxxxxxxxxx; Tian, Kevin; Zhang, Yang Z > Subject: Re: [RESEND] nested EPT: fix the handling of nested EPT. > > At 05:06 +0800 on 03 Jun (1433307971), Liang Li wrote: > > If the host EPT entry is changed, the nested EPT should be updated. > > The current code does not do this, and it's wrong. > > > > Reported-by: Tim Deegan <tim@xxxxxxx> > > Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx> > > Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx> > > --- > > xen/arch/x86/mm/p2m-ept.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c > > index 5133eb6..26293a0 100644 > > --- a/xen/arch/x86/mm/p2m-ept.c > > +++ b/xen/arch/x86/mm/p2m-ept.c > > @@ -26,6 +26,7 @@ > > #include <asm/p2m.h> > > #include <asm/hvm/vmx/vmx.h> > > #include <asm/hvm/vmx/vmcs.h> > > +#include <asm/hvm/nestedhvm.h> > > #include <xen/iommu.h> > > #include <asm/mtrr.h> > > #include <asm/hvm/cacheattr.h> > > @@ -1076,6 +1077,9 @@ void ept_sync_domain(struct p2m_domain *p2m) > > > > ASSERT(local_irq_is_enabled()); > > > > + if ( nestedhvm_enabled(d) ) > > + p2m_flush_nestedp2m(d); > > > It seems like this should trigger when the nested EPT table itself is being > populated, e.g. > > hvm_hap_nested_page_fault > --> nestedhvm_hap_nested_page_fault > --> nestedhap_fix_p2m (--> p2m_lock(p2m)) > --> p2m_set_entry > --> ept_set_entry > --> ept_sync_domain > --> p2m_flush_nestedp2m > --> p2m_flush_table (--> p2m_lock(p2m)) > > which would deadlock on the nested table's p2m lock. What have I missed? Yes, you are right. Maybe we should add another condition checking, just like: struct vcpu *v = current; If(nestedhvm_enabled(d) && !nestedhvm_vcpu_in_guestmode(v) ) p2m_flush_nestedp2m(d); Or add a flag(is_nested_p2m) in the struct p2m_domain to mark a nested EPT, and change the condition to: If(nestedhvm_enabled(d) && p2m->is_nested_p2m ) to exclude the case of nested EPT, is that enough? Liang > Tim. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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