Re: [v1][KVM][PATCH 1/1] kvm:ppc:booehv: direct ISI exception to Guest

["tiejun.chen" <tiejun.chen@windriver.com>]

On 05/08/2013 05:20 PM, Caraman Mihai Claudiu-B02008 wrote:
>> -----Original Message-----
>> From: kvm-owner@vger.kernel.org [mailto:kvm-owner@vger.kernel.org] On
>> Behalf Of tiejun.chen
>> Sent: Wednesday, May 08, 2013 4:54 AM
>> To: Wood Scott-B07421
>> Cc: agraf@suse.de; kvm-ppc@vger.kernel.org; kvm@vger.kernel.org;
>> linuxppc-dev@lists.ozlabs.org
>> Subject: Re: [v1][KVM][PATCH 1/1] kvm:ppc:booehv: direct ISI exception to
>> Guest
>>
>> On 05/08/2013 07:40 AM, Scott Wood wrote:
>>> On 05/07/2013 06:06:30 AM, Tiejun Chen wrote:
>>>> We also can direct ISI exception to Guest like DSI.
>>>>
>>>> Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
>>>> ---
>>>>   arch/powerpc/kvm/booke_emulate.c |    3 +++
>>>>   arch/powerpc/kvm/e500mc.c        |    3 ++-
>>>>   2 files changed, 5 insertions(+), 1 deletion(-)
>>>
>>> Are you seeing a real performance improvement from this?  This will
>> interfere
>>
>> No. But after we reduce the exit to host, shouldn't this improve
>> performance?
>
> We lose some flexibility for this so it make sense only if we gain
> measurable improvements.

Sounds we have much more works to do.

>
>>
>>> somewhat with using the VF bit, if we were to ever do so, since VF only
>> affects
>>
>> Sorry, what is the VF you said?
>
> VF stands for virtualization fault see MAS8[VF] and we may use it for virtualized

I almost forget this point :)

> MMIO. The hypervisor should deny execute access on pages marked with VF. Accordingly
> in this case guest ISI exceptions should be handled by the hypervisor.

Thanks for your information.

Tiejun