Re: [Xen-devel] [PATCH 02/11] VMX: implement suppress #VE.

[Ed White <edmund.h.white@xxxxxxxxx>]

On 01/15/2015 10:46 AM, Ed White wrote:
> On 01/15/2015 08:25 AM, Tim Deegan wrote:
>> Hi,
>>
>> At 13:26 -0800 on 09 Jan (1420806392), Ed White wrote:
>>>  static inline bool_t is_epte_valid(ept_entry_t *e)
>>>  {
>>> -    return (e->epte != 0 && e->sa_p2mt != p2m_invalid);
>>> +    return (e->valid != 0 && e->sa_p2mt != p2m_invalid);
>>
>> This test for 0 is just catching uninitialised entries in freshly
>> allocated pages.  Rather than changing it to ignore bit 63, this loop...
>>
>>>  }
>>>  
>>>  /* returns : 0 for success, -errno otherwise */
>>> @@ -194,6 +194,19 @@ static int ept_set_middle_entry(struct p2m_domain 
>>> *p2m, ept_entry_t *ept_entry)
>>>  
>>>      ept_entry->r = ept_entry->w = ept_entry->x = 1;
>>>  
>>> +    /* Disable #VE on all entries */ 
>>> +    if ( cpu_has_vmx_virt_exceptions )
>>> +    {
>>> +        ept_entry_t *table = __map_domain_page(pg);
>>> +
>>> +        for ( int i = 0; i < EPT_PAGETABLE_ENTRIES; i++ )
>>> +            table[i].suppress_ve = 1;
>>
>> ...should set the type of the empty entries to p2m_invalid as it goes.
>>
>>> +    /* Disable #VE on all entries */
>>> +    if ( cpu_has_vmx_virt_exceptions )
>>> +    {
>>> +        ept_entry_t *table =
>>> +            map_domain_page(pagetable_get_pfn(p2m_get_pagetable(p2m)));
>>> +
>>> +        for ( int i = 0; i < EPT_PAGETABLE_ENTRIES; i++ )
>>> +            table[i].suppress_ve = 1;
>>
>> And the same here.

I have some time to work on this patch series again, and although I tried
this it doesn't eliminate all the instances of epte being zero with the
possible exception of suppress_ve. I spent some time trying to find all
cases where that happens without success, so I've used Andrew's suggestion
of using a mask.

Ed

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