From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tim Deegan <tim@xen.org>
Subject: Re: Deadlocks by p2m_lock and event_lock
Date: Fri, 9 Mar 2012 16:55:44 +0000
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To: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Cc: Keir Fraser <keir@xen.org>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, "Hao, Xudong" <xudong.hao@intel.com>, "JBeulich@suse.com" <jbeulich@suse.com>, "Zhang,
	Xiantao" <xiantao.zhang@intel.com>
List-Id: xen-devel@lists.xenproject.org

At 08:29 -0800 on 09 Mar (1331281767), Andres Lagar-Cavilla wrote:
> >> I don't know about the event lock, but it seems unwise to call in to
> >> handle_mmio with a gfn lock held.  How about fixing the other path?
> >>
> >> diff -r 04673ecb9d78 xen/arch/x86/hvm/hvm.c
> >> --- a/xen/arch/x86/hvm/hvm.c	Thu Mar 08 16:40:05 2012 +0000
> >> +++ b/xen/arch/x86/hvm/hvm.c	Fri Mar 09 11:15:25 2012 +0000
> >> @@ -1324,10 +1324,11 @@ int hvm_hap_nested_page_fault(unsigned l
> >>      if ( (p2mt == p2m_mmio_dm) ||
> >>           (access_w && (p2mt == p2m_ram_ro)) )
> >>      {
> >> +        put_gfn(p2m->domain, gfn);
> >>          if ( !handle_mmio() )
> >>              hvm_inject_exception(TRAP_gp_fault, 0, 0);
> >>          rc = 1;
> >> -        goto out_put_gfn;
> >> +        goto out;
> >>      }
> >>
> >>  #ifdef __x86_64__
> >> @@ -1379,6 +1380,7 @@ int hvm_hap_nested_page_fault(unsigned l
> >>
> >>  out_put_gfn:
> >>      put_gfn(p2m->domain, gfn);
> >> +out:
> >>      if ( paged )
> >>          p2m_mem_paging_populate(v->domain, gfn);
> >>      if ( req_ptr )
> >
> > Yes, that's fine to release the p2m lock earlier than handle_mmio.
> 
> Ack

OK, applied.

Tim.