Re: [Xen-devel] [PATCH v2] nested VMX: fix I/O port exit emulation

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 03/12/13 15:55, Jan Beulich wrote:
>>>> On 03.12.13 at 15:30, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>>> @@ -2220,15 +2219,23 @@ int nvmx_n2_vmexit_handler(struct cpu_us
>>>          if ( ctrl & CPU_BASED_ACTIVATE_IO_BITMAP )
>>>          {
>>>              unsigned long qual;
>>> -            u16 port;
>>> +            u16 port, size;
>>>  
>>>              __vmread(EXIT_QUALIFICATION, &qual);
>>>              port = qual >> 16;
>>> -            bitmap = nvmx->iobitmap[port >> 15];
>>> -            if ( bitmap[(port & 0x7fff) >> 3] & (1 << (port & 0x7)) )
>>> -                nvcpu->nv_vmexit_pending = 1;
>>> +            size = (qual & 7) + 1;
>> This should be (qual & 3) for the correct size (Bit 3 is the
>> direction).
> Right - bit 3 is the direction. Bits 0..2 are the size. Hence the
> mask ought to be 7.

D'oh - I cant count, even with the manual for reference.

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

>
>>  Is it worth also verifying that ((qual & 3) != 2)?
> I don't think so - there's no harm to our code here if an undefined
> value was there.
>
> Jan
>


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