Re: [Xen-devel] [RESEND] nested EPT: fix the handling of nested EPT.

[Tim Deegan <tim@xxxxxxx>]

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?

Tim.

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