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

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 08/02/17 17:29, Tim Deegan wrote:
> 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>

Right -- I'll change it to the usual idiom and check it in after I've
gotten a test report (or waited a reasonable amount of time).

 -George


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