Re: [PATCH V3 28/29] x86/vvtd: Add queued invalidation (QI) support

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Gao, Chao
> Sent: Monday, October 23, 2017 4:52 PM
> 
> On Mon, Oct 23, 2017 at 09:57:16AM +0100, Roger Pau Monné wrote:
> >On Mon, Oct 23, 2017 at 03:50:24PM +0800, Chao Gao wrote:
> >> On Fri, Oct 20, 2017 at 12:20:06PM +0100, Roger Pau Monné wrote:
> >> >On Thu, Sep 21, 2017 at 11:02:09PM -0400, Lan Tianyu wrote:
> >> >> From: Chao Gao <chao.gao@intel.com>
> >> >> +    }
> >> >> +
> >> >> +    unmap_guest_page((void*)qinval_page);
> >> >> +    return ret;
> >> >> +
> >> >> + error:
> >> >> +    unmap_guest_page((void*)qinval_page);
> >> >> +    gdprintk(XENLOG_ERR, "Internal error in Queue Invalidation.\n");
> >> >> +    domain_crash(vvtd->domain);
> >> >
> >> >Do you really need to crash the domain in such case?
> >>
> >> We reach here when guest requests some operations vvtd doesn't claim
> >> supported or emulated. I am afraid it also can be triggered by guest.
> >> How about ignoring the invalidation request?
> >
> >What would real hardware do in such case?
> 
> After reading the spec again, I think hardware may generate a fault
> event, seeing VT-d spec 10.4.9 Fault Status Register:
> Hardware detected an error associated with the invalidation queue. This
> could be due to either a hardware error while fetching a descriptor from
> the invalidation queue, or hardware detecting an erroneous or invalid
> descriptor in the invalidation queue. At this time, a fault event may be
> generated based on the programming of the Fault Event Control register
> 

Please do proper emulation according to hardware behavior.

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