Re: [Xen-devel] [PATCH v2] xen/p2m: Fix p2m_flush_table for non-nested cases

[Tim Deegan <tim@xxxxxxx>]

At 17:22 +0000 on 08 Feb (1486574546), George Dunlap wrote:
> Commit 71bb7304e7a7a35ea6df4b0cedebc35028e4c159 added flushing of
> nested p2m tables whenever the host p2m table changed.  Unfortunately
> in the process, it added a filter to p2m_flush_table() function so
> that the p2m would only be flushed if it was being used as a nested
> p2m.  This meant that the p2m was not being flushed at all for altp2m
> callers.
> 
> Only check np2m_base if p2m_class is set to p2m_nested.
> 
> NB that this is not a security issue: The only time this codepath is
> called is in cases where either nestedp2m or altp2m is enabled, and
> neither of them are in security support.
> 
> Reported-by: Matt Leinhos <matt@xxxxxxxxxx>
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> CC: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
> ---
>  xen/arch/x86/mm/p2m.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index 6548e9f..0af2ec1 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1627,7 +1627,9 @@ p2m_flush_table(struct p2m_domain *p2m)
>      ASSERT(page_list_empty(&p2m->pod.super));
>      ASSERT(page_list_empty(&p2m->pod.single));
>  
> -    if ( p2m->np2m_base == P2M_BASE_EADDR )
> +    /* No need to flush if it's already empty */
> +    if ( p2m->p2m_class == p2m_nested &&
> +         p2m->np2m_base == P2M_BASE_EADDR )

Looks like p2m_is_nestedp2m(p2m) is the usual idiom.  Either way:

Reviewed-by: Tim Deegan <tim@xxxxxxx>

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