Re: [Xen-devel] [PATCH V3 13/29] x86/vvtd: Set Interrupt Remapping Table Pointer through GCMD

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.10.17 at 06:08, <chao.gao@xxxxxxxxx> wrote:
> On Thu, Oct 19, 2017 at 12:56:45PM +0100, Roger Pau Monné wrote:
>>On Thu, Sep 21, 2017 at 11:01:54PM -0400, Lan Tianyu wrote:
>>> @@ -148,6 +205,18 @@ static int vvtd_write(struct vcpu *v, unsigned long 
>>> addr,
>>>              break;
>>>          }
>>>      }
>>> +    else /* len == 8 */
>>> +    {
>>> +        switch ( offset )
>>> +        {
>>> +        case DMAR_IRTA_REG:
>>> +            vvtd_set_reg_quad(vvtd, DMAR_IRTA_REG, val);
>>
>>I have kind of a generic comment regarding the handlers in general,
>>which I will just make here. Don't you need some kind of locking to
>>prevent concurrent read/write accesses to the registers?
> 
> I think guest should be responsible to avoid concurrency.
> Xen only needs to not be fooled (crashed) by a malicious guest.

But can you assure this without doing some locking yourself?

Jan

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