From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Kiszka <jan.kiszka@web.de>
Subject: Re: Host latency peaks due to kvm-intel
Date: Sun, 26 Jul 2009 16:34:24 +0200
Message-ID: <4A6C6970.6060200@web.de>
References: <4A68A6E5.6010808@siemens.com> <4A68BD5D.1070302@gmail.com> <4A6981B0.3000008@siemens.com> <4A6B1C15.6090608@redhat.com>
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Cc: Gregory Haskins <gregory.haskins@gmail.com>,
	kvm-devel <kvm@vger.kernel.org>,
	RT <linux-rt-users@vger.kernel.org>,
	"Yang, Sheng" <sheng.yang@intel.com>
To: Avi Kivity <avi@redhat.com>
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Avi Kivity wrote:
> On 07/24/2009 12:41 PM, Jan Kiszka wrote:
>> Jan (who is now patching his guest to avoid wbinvd where possible)
>>
>>   =20
>=20
> Is there ever a case where it is required?  What about under a
> hypervisor (i.e. check the hypervisor enabled bit).
>=20

Reminds me of the discussion in '07 when I first stumbled over this :) :
Yes, the bochs bios could safely skip the wbinvd in qemu mode. But that
won't safe us from Linux and - far more problematic - Windows or any
binary-only guest which think they have to issue it.

One may the close eyes, fire up the guest and then start the
time-critical host application in the hope that the guest remains calm
as long as it's up and running. But, well...

Jan


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