Re: [PATCH] pvh: Fix regression caused by assumption that HVM paths MUST use io-backend device.

[George Dunlap <george.dunlap@eu.citrix.com>]

On 02/04/2014 04:42 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Feb 04, 2014 at 03:46:48PM +0000, Jan Beulich wrote:
>>>>> On 04.02.14 at 16:32, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
>>> On Tue, Feb 04, 2014 at 03:02:44PM +0000, Jan Beulich wrote:
>>>> Wasn't it that Mukesh's patch simply was yours with the two
>>>> get_ioreq()s folded by using a local variable?
>>> Yes. As so
>> Thanks. Except that ...
>>
>>> --- a/xen/arch/x86/hvm/vmx/vvmx.c
>>> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
>>> @@ -1394,13 +1394,13 @@ void nvmx_switch_guest(void)
>>>       struct vcpu *v = current;
>>>       struct nestedvcpu *nvcpu = &vcpu_nestedhvm(v);
>>>       struct cpu_user_regs *regs = guest_cpu_user_regs();
>>> -
>>> +    ioreq_t *p = get_ioreq(v);
>> ... you don't want to drop the blank line, and naming the new
>> variable "ioreq" would seem preferable.
>>
>>>       /*
>>>        * a pending IO emualtion may still no finished. In this case,
>>>        * no virtual vmswith is allowed. Or else, the following IO
>>>        * emulation will handled in a wrong VCPU context.
>>>        */
>>> -    if ( get_ioreq(v)->state != STATE_IOREQ_NONE )
>>> +    if ( p && p->state != STATE_IOREQ_NONE )
>> And, as said before, I'd think "!p ||" instead of "p &&" would be
>> the right thing here. Yang, Jun?
> I have two patches - one the simpler one that is pretty straightfoward
> and the one you suggested. Either one fixes PVH guests. I also did
> bootup tests with HVM guests to make sure they worked.
>
> Attached and inline.

But they do different things -- one does "ioreq && ioreq->state..." and 
the other does "!ioreq || ioreq->state...".  The first one is incorrect, 
AFAICT.

  -George