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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Jan Beulich <JBeulich@suse.com>, Chao Gao <chao.gao@intel.com>
Cc: Juergen Gross <jgross@suse.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ankur Arora <ankur.a.arora@oracle.com>,
	xen-devel@lists.xen.org
Subject: Re: [PATCH] x86/vlapic: Don't reset APIC mode/ID when handling INIT signal
Date: Wed, 19 Apr 2017 09:43:15 -0400	[thread overview]
Message-ID: <05d39fae-c8ba-292b-9f16-3caf31087d1c@oracle.com> (raw)
In-Reply-To: <58F780600200007800151F2E@prv-mh.provo.novell.com>



On 04/19/2017 09:21 AM, Jan Beulich wrote:
>>>> On 19.04.17 at 06:56, <chao.gao@intel.com> wrote:
>> On Wed, Apr 19, 2017 at 02:48:57AM -0600, Jan Beulich wrote:
>>>>>> On 18.04.17 at 23:51, <chao.gao@intel.com> wrote:
>>>> HVM guest can't enable x2apic as XENFEAT_hvm_pirqs is exposed to it.
>>>> Why we have this restriction? As a consequence, This patch isn't
>>>> tested in that case.
>>>
>>> HVM guests very well can use x2APIC, I'm seeing them use it all
>>> the time. Please be more specific with your question.
>>
>> OK. I failed to enable guest's x2apic, with the output: IRQ Remapping doesn't
>> support X2APIC mode. Eventually, I found the xen_x2apic_para_available()
>> in linux kernel and it returns false when Xen exposes XENFEAT_hvm_pirqs to
>> guest.
>
> Looks more like a Linux/pvops question, which I continue to not
> really be an expert on. Let's ask the maintainers (now Cc-ed)
> (but it may well be that this simply depends on whether you
> enable PVHVM mode)...

Interestingly enough, I was looking at this last week and wondering why 
it was there. Ankur (copied) found an issue related to x2apic he thought 
was PVH-specific, but that was because HVM guests don't turn it on.

Konrad couldn't remember why it was there neither.

-boris

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  reply	other threads:[~2017-04-19 13:43 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-18 21:51 [PATCH] x86/vlapic: Don't reset APIC mode/ID when handling INIT signal Chao Gao
2017-04-19  8:48 ` Jan Beulich
2017-04-19  4:56   ` Chao Gao
2017-04-19 13:21     ` Jan Beulich
2017-04-19 13:43       ` Boris Ostrovsky [this message]
2017-04-19 13:58         ` Juergen Gross
2017-04-19 14:13           ` Juergen Gross

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