From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: KVM: MMU: handle invalid root_hpa at __direct_map
Date: Fri, 20 Dec 2013 10:59:09 -0200
Message-ID: <20131220125908.GA3996@amt.cnet>
References: <20131219172850.GA22588@amt.cnet>
 <52B40A96.7070809@linux.vnet.ibm.com>
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Cc: kvm-devel <kvm@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>
To: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
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On Fri, Dec 20, 2013 at 05:15:02PM +0800, Xiao Guangrong wrote:
> On 12/20/2013 01:28 AM, Marcelo Tosatti wrote:
> > 
> > It is possible for __direct_map to be called on invalid root_hpa
> > (-1), two examples:
> > 
> > 1) try_async_pf -> can_do_async_pf
> >     -> vmx_interrupt_allowed -> nested_vmx_vmexit
> > 2) vmx_handle_exit -> vmx_interrupt_allowed -> nested_vmx_vmexit
> > 
> > Then to load_vmcs12_host_state and kvm_mmu_reset_context.
> > 
> > Check for this possibility, let fault exception be regenerated.
> > 
> > BZ: https://bugzilla.redhat.com/show_bug.cgi?id=924916
> > 
> 
> Nice catch, Marcelo!
> Isn't it better to do kvm_mmu_reload() before calling page_fault handler?
> Then a #PF can be avoided.

try_async_pf can be called from within the page fault handler.