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From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
	Eduardo Habkost <ehabkost@redhat.com>
Cc: "Wanpeng Li" <kernellwp@gmail.com>,
	qemu-devel@nongnu.org, kvm@vger.kernel.org,
	"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS
Date: Wed, 16 May 2018 14:44:24 +0200	[thread overview]
Message-ID: <c4f7f4bd-80ce-3d84-fb0d-a7ac22333afd@redhat.com> (raw)
In-Reply-To: <20180512010007-mutt-send-email-mst@kernel.org>

On 12/05/2018 00:12, Michael S. Tsirkin wrote:
>> Maybe it's a better idea than overloading an option that is only
>> expected to control a CPUID bit.
> Well -realtime would be a bit confusing in that it enables mlock by
> default.

Currently, the only suboption of "-realtime" is mlock, which means that
the only three valid uses of it are

	-realtime mlock=on
	-realtime mlock=off
	-realtime ''

We can change the default, I think.  Only the third would change
meaning, and it's a slightly crazy way to use the option.

> From pure API point of view, hint-dedicated looks good since
> it seems to say "optimize for a dedicated host CPU" and
> it's a hint in that guests keep working if you violate this
> slightly once in a while.
> 
> But I agree there's a problem: right now "kvm-" means "KVM PV"
> as opposed to e.g. HV enlightened gusts.
> So if you enable hyperv and also want to disable halt existing,
> what then? What should kvm-hint-dedicated=on do?

kvm-hint-dedicated=on only sets the CPUID bit, which Linux for example
uses that to disable pv spinlocks.  "-realtime dedicated-cpus=on" only
disables the vmexits.  You can use the two independently.

Thanks,

Paolo

> So how about a new hint-dedicated=on cpu flag?  We can have that set
> kvm-hint-dedicated if kvm PV is enabled.
> 

  parent reply	other threads:[~2018-05-16 12:44 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-17  8:24 [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS Wanpeng Li
2018-04-17  8:28 ` no-reply
2018-04-17 18:08 ` Michael S. Tsirkin
2018-04-18  1:09   ` Wanpeng Li
2018-05-11 21:57     ` Michael S. Tsirkin
2018-05-12  0:49       ` Wanpeng Li
2018-04-17 20:59 ` Eduardo Habkost
2018-04-18  1:20   ` Wanpeng Li
2018-04-19 15:48   ` Paolo Bonzini
2018-04-19 19:56     ` Eduardo Habkost
2018-04-19 21:32       ` Paolo Bonzini
2018-04-19 21:53         ` Eduardo Habkost
2018-05-11 22:12           ` Michael S. Tsirkin
2018-05-16 12:34             ` Eduardo Habkost
2018-05-16 14:26               ` Michael S. Tsirkin
2018-05-17 17:34                 ` Eduardo Habkost
2018-05-17 17:57                   ` Michael S. Tsirkin
2018-05-17 18:18                     ` Eduardo Habkost
2018-05-16 12:44             ` Paolo Bonzini [this message]
2018-05-16 14:22               ` Michael S. Tsirkin
2018-05-16 15:04                 ` Paolo Bonzini
2018-05-16 15:13                   ` Michael S. Tsirkin
2018-05-16 15:33                     ` Eduardo Habkost
2018-05-16 16:21                       ` Michael S. Tsirkin
2018-05-16 17:20                         ` Eduardo Habkost

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