From: George Dunlap <george.dunlap@citrix.com>
To: "Wu, Feng" <feng.wu@intel.com>,
Dario Faggioli <dario.faggioli@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
"keir@xen.org" <keir@xen.org>,
"george.dunlap@eu.citrix.com" <george.dunlap@eu.citrix.com>,
"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
"jbeulich@suse.com" <jbeulich@suse.com>
Subject: Re: [PATCH v2 0/4] VMX: Properly handle pi descriptor and per-cpu blocking list
Date: Fri, 24 Jun 2016 14:49:18 +0100 [thread overview]
Message-ID: <d22bc57a-caa2-5238-5c19-8a3cbec90cec@citrix.com> (raw)
In-Reply-To: <E959C4978C3B6342920538CF579893F01972EE64@SHSMSX103.ccr.corp.intel.com>
On 24/06/16 14:42, Wu, Feng wrote:
>
>
>> -----Original Message-----
>> From: Dario Faggioli [mailto:dario.faggioli@citrix.com]
>> Sent: Friday, June 24, 2016 6:29 PM
>> To: Wu, Feng <feng.wu@intel.com>; xen-devel@lists.xen.org
>> Cc: keir@xen.org; Tian, Kevin <kevin.tian@intel.com>; jbeulich@suse.com;
>> andrew.cooper3@citrix.com; george.dunlap@eu.citrix.com;
>> konrad.wilk@oracle.com
>> Subject: Re: [PATCH v2 0/4] VMX: Properly handle pi descriptor and per-cpu
>> blocking list
>>
>> On Fri, 2016-06-24 at 06:33 +0000, Wu, Feng wrote:
>>>> -----Original Message-----
>>>> From: Dario Faggioli [mailto:dario.faggioli@citrix.com]
>>>> In your case, AFAICUI, it's:
>>>> - the vCPU should block, waiting for an event
>>>> - the event is _not_ arrived, so we indeed should block
>>>> - we do *not* block, due to some other reason
>>>>
>>>> That does not look right to me... what about the fact that we
>>>> wanted to
>>>> actually wait for the event? :-O
>>> I understand your point. In my understanding, currently, vcpu_block()
>>> is
>>> for guest's HLT operation, which means, guest has nothing to do. In
>>> this case, even we return (not blocking), seems the function is not
>>> broken.
>>>
>> So, basically, you're saying that the vcpu has nothing to do, and in
>> fact it executed an HLT instruction, and you want to let it continue to
>> run? :-O
>
> Here is my understanding, if the guest has nothing to do, it will
> call HLT, and Xen hypervisor will call vcpu_block(), if we don't
> block the vCPU and return to guest, guest will continue to run
> HLT if it still has nothing to do.
As it happens, most operating systems will handle this situation just
fine; but I'm not sure this is something we want to rely on.
-George
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next prev parent reply other threads:[~2016-06-24 13:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-26 13:39 [PATCH v2 0/4] VMX: Properly handle pi descriptor and per-cpu blocking list Feng Wu
2016-05-26 13:39 ` [PATCH v2 1/4] VMX: Properly handle pi when all the assigned devices are removed Feng Wu
2016-05-27 13:43 ` Jan Beulich
2016-05-31 10:22 ` Wu, Feng
2016-05-31 11:52 ` Jan Beulich
2016-06-03 5:12 ` Wu, Feng
2016-06-03 9:45 ` Jan Beulich
2016-05-26 13:39 ` [PATCH v2 2/4] VMX: Cleanup PI per-cpu blocking list when vcpu is destroyed Feng Wu
2016-05-27 13:49 ` Jan Beulich
2016-05-31 10:22 ` Wu, Feng
2016-05-31 11:54 ` Jan Beulich
2016-05-26 13:39 ` [PATCH v2 3/4] VMX: Assign the right value to 'NDST' field in a concern case Feng Wu
2016-05-27 14:00 ` Jan Beulich
2016-05-31 10:27 ` Wu, Feng
2016-05-31 11:58 ` Jan Beulich
2016-06-03 5:23 ` Wu, Feng
2016-06-03 9:57 ` Jan Beulich
2016-06-22 18:00 ` George Dunlap
2016-06-24 9:08 ` Wu, Feng
2016-05-26 13:39 ` [PATCH v2 4/4] VMX: fixup PI descritpor when cpu is offline Feng Wu
2016-05-27 14:56 ` Jan Beulich
2016-05-31 10:31 ` Wu, Feng
2016-06-22 18:33 ` George Dunlap
2016-06-24 6:34 ` Wu, Feng
2016-05-26 17:20 ` [PATCH v2 0/4] VMX: Properly handle pi descriptor and per-cpu blocking list Dario Faggioli
2016-05-31 10:19 ` Wu, Feng
2016-06-22 21:33 ` Dario Faggioli
2016-06-24 6:33 ` Wu, Feng
2016-06-24 10:29 ` Dario Faggioli
2016-06-24 13:42 ` Wu, Feng
2016-06-24 13:49 ` George Dunlap [this message]
2016-06-24 14:36 ` Dario Faggioli
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