Re: [Xen-devel] [PATCH 1/2] x86/HVM: latch linear->phys translation results

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 20/06/16 14:12, Tim Deegan wrote:
> At 12:54 +0100 on 09 Jun (1465476894), Andrew Cooper wrote:
>> On 08/06/16 14:09, Jan Beulich wrote:
>>> ... to avoid re-doing the same translation later again (in a retry, for
>>> example). This doesn't help very often according to my testing, but
>>> it's pretty cheap to have, and will be of further use subsequently.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>
>>> --- a/xen/arch/x86/hvm/emulate.c
>>> +++ b/xen/arch/x86/hvm/emulate.c
>>> @@ -678,6 +678,19 @@ static struct hvm_mmio_cache *hvmemul_fi
>>>      return cache;
>>>  }
>>>  
>>> +static void latch_linear_to_phys(struct hvm_vcpu_io *vio, unsigned long 
>>> gla,
>>> +                                 unsigned long gpa, bool_t write)
>>> +{
>>> +    if ( vio->mmio_access.gla_valid )
>>> +        return;
>>> +
>>> +    vio->mmio_gva = gla & PAGE_MASK;
>> This suggest that mmio_vga is mis-named.
>>
>> Looking at the uses, handle_mmio_with_translation() is used
>> inconsistently, with virtual addresses from the shadow code, but linear
>> addresses from nested hap code.
>>
>> Clearly one of these two users are buggy for guests running in a non
>> flat way, and it looks to be the shadow side which is buggy.
> Yes, the naming in the shadow code is incorrect.  Shadow code, along
> with a lot of Xen code, uses "virtual" to refer to what the manuals
> call linear addresses, i.e. the inputs to paging.  IIRC it was only
> with the introduction of HAP hardware interfaces that we started using
> the term "linear" widely in Xen code.
>
> I will ack a mechanical renaming if you like, though beware of public
> interfaces with the old name, and common code ("linear" being an x86
> term).

I will be doing some cleanup in due course, although I don't have enough
time to do this right now.

~Andrew

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