Re: [Qemu-devel] [RFC] Next gen kvm api

[Scott Wood]

On 02/16/2012 06:23 PM, Alexander Graf wrote:
> On 16.02.2012, at 21:41, Scott Wood wrote:
>> And yes, we do have fancier hardware coming fairly soon for which this
>> breaks (TLB0 entries can be loaded without host involvement, as long as
>> there's a translation from guest physical to physical in a separate
>> hardware table).  It'd be reasonable to ignore TLB0 for migration (treat
>> it as invalidated), but not for debug since that may be where the
>> translation we're interested in resides.
> 
> Could we maybe add an ioctl that forces kvm to read out the current tlb0 
> contents and push them to memory? How slow would that be?

Yes, I was thinking something like that.  We'd just have to remove (make
conditional on MMU type) the statement that this is synchronized
implicitly on return from vcpu_run.

Performance shouldn't be a problem -- we'd only need to sync once and
then can do all the repeated debug accesses we want.  So should be no
need to mess around with partial sync.

-Scott