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Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS |
Date: |
Wed, 16 May 2018 17:22:10 +0300 |
On Wed, May 16, 2018 at 02:44:24PM +0200, Paolo Bonzini wrote:
> 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.
But when would you want to 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.
> >
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Michael S. Tsirkin, 2018/05/11
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Michael S. Tsirkin, 2018/05/11
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Eduardo Habkost, 2018/05/16
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Paolo Bonzini, 2018/05/16
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Paolo Bonzini, 2018/05/16
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Michael S. Tsirkin, 2018/05/16
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Eduardo Habkost, 2018/05/16
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Michael S. Tsirkin, 2018/05/16
- Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS, Eduardo Habkost, 2018/05/16