Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-26 Thread Roman Kagan
On Fri, Mar 23, 2018 at 04:48:27PM -0300, Eduardo Habkost wrote: > On Fri, Mar 23, 2018 at 12:45:30PM +0300, Roman Kagan wrote: > > On Thu, Mar 22, 2018 at 03:38:13PM -0300, Eduardo Habkost wrote: > > > It looks like the guest can still crash if we migrate > > > "QEMU-2.12 -machine pc-2.11 -cpu

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-23 Thread Eduardo Habkost
On Fri, Mar 23, 2018 at 12:45:30PM +0300, Roman Kagan wrote: > On Thu, Mar 22, 2018 at 03:38:13PM -0300, Eduardo Habkost wrote: > > On Thu, Mar 22, 2018 at 04:58:03PM +0300, Roman Kagan wrote: > > > On Thu, Mar 22, 2018 at 10:22:18AM -0300, Eduardo Habkost wrote: > > > > On Thu, Mar 22, 2018 at

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-23 Thread Roman Kagan
On Thu, Mar 22, 2018 at 03:38:13PM -0300, Eduardo Habkost wrote: > On Thu, Mar 22, 2018 at 04:58:03PM +0300, Roman Kagan wrote: > > On Thu, Mar 22, 2018 at 10:22:18AM -0300, Eduardo Habkost wrote: > > > On Thu, Mar 22, 2018 at 04:00:14PM +0300, Roman Kagan wrote: > > > > On Wed, Mar 21, 2018 at

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-22 Thread Eduardo Habkost
On Thu, Mar 22, 2018 at 04:58:03PM +0300, Roman Kagan wrote: > On Thu, Mar 22, 2018 at 10:22:18AM -0300, Eduardo Habkost wrote: > > On Thu, Mar 22, 2018 at 04:00:14PM +0300, Roman Kagan wrote: > > > On Wed, Mar 21, 2018 at 05:19:24PM -0300, Eduardo Habkost wrote: > > > > On Wed, Mar 21, 2018 at

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-22 Thread Roman Kagan
On Thu, Mar 22, 2018 at 10:22:18AM -0300, Eduardo Habkost wrote: > On Thu, Mar 22, 2018 at 04:00:14PM +0300, Roman Kagan wrote: > > On Wed, Mar 21, 2018 at 05:19:24PM -0300, Eduardo Habkost wrote: > > > On Wed, Mar 21, 2018 at 07:57:29PM +0300, Roman Kagan wrote: > > > > On Wed, Mar 21, 2018 at

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-22 Thread Eduardo Habkost
On Thu, Mar 22, 2018 at 04:00:14PM +0300, Roman Kagan wrote: > On Wed, Mar 21, 2018 at 05:19:24PM -0300, Eduardo Habkost wrote: > > On Wed, Mar 21, 2018 at 07:57:29PM +0300, Roman Kagan wrote: > > > On Wed, Mar 21, 2018 at 02:18:54PM +0100, Vitaly Kuznetsov wrote: > > > > Roman Kagan

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-22 Thread Roman Kagan
On Wed, Mar 21, 2018 at 05:19:24PM -0300, Eduardo Habkost wrote: > On Wed, Mar 21, 2018 at 07:57:29PM +0300, Roman Kagan wrote: > > On Wed, Mar 21, 2018 at 02:18:54PM +0100, Vitaly Kuznetsov wrote: > > > Roman Kagan writes: > > > > > > > On Tue, Mar 20, 2018 at 06:35:00PM

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Eduardo Habkost
On Wed, Mar 21, 2018 at 07:57:29PM +0300, Roman Kagan wrote: > On Wed, Mar 21, 2018 at 02:18:54PM +0100, Vitaly Kuznetsov wrote: > > Roman Kagan writes: > > > > > On Tue, Mar 20, 2018 at 06:35:00PM +0100, Vitaly Kuznetsov wrote: > > >> Requiring tsc_is_stable_and_known() is

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Eduardo Habkost
On Wed, Mar 21, 2018 at 08:17:55PM +0300, Roman Kagan wrote: > On Wed, Mar 21, 2018 at 05:17:38PM +0100, Vitaly Kuznetsov wrote: > > (What I'm worried about with all our hv_* knobs is that more of them we > > have easier it is to assemble some frankenstien which won't look like > > any existing

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Roman Kagan
On Wed, Mar 21, 2018 at 05:17:38PM +0100, Vitaly Kuznetsov wrote: > (What I'm worried about with all our hv_* knobs is that more of them we > have easier it is to assemble some frankenstien which won't look like > any existing Hyper-V version; we're probably not doing a very good job > tesing all

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Roman Kagan
On Wed, Mar 21, 2018 at 02:18:54PM +0100, Vitaly Kuznetsov wrote: > Roman Kagan writes: > > > On Tue, Mar 20, 2018 at 06:35:00PM +0100, Vitaly Kuznetsov wrote: > >> Requiring tsc_is_stable_and_known() is too restrictive: even without INVTCS > >> nested Hyper-V-on-KVM

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Roman Kagan
On Wed, Mar 21, 2018 at 04:33:33PM +0100, Paolo Bonzini wrote: > On 20/03/2018 18:35, Vitaly Kuznetsov wrote: > > +if (has_msr_hv_frequencies && env->tsc_khz) { > > env->features[FEAT_HYPERV_EAX] |= HV_ACCESS_FREQUENCY_MSRS; > > env->features[FEAT_HYPERV_EDX] |=

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Vitaly Kuznetsov
Paolo Bonzini writes: > On 20/03/2018 18:35, Vitaly Kuznetsov wrote: >> +if (has_msr_hv_frequencies && env->tsc_khz) { >> env->features[FEAT_HYPERV_EAX] |= HV_ACCESS_FREQUENCY_MSRS; >> env->features[FEAT_HYPERV_EDX] |=

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Paolo Bonzini
On 20/03/2018 18:35, Vitaly Kuznetsov wrote: > +if (has_msr_hv_frequencies && env->tsc_khz) { > env->features[FEAT_HYPERV_EAX] |= HV_ACCESS_FREQUENCY_MSRS; > env->features[FEAT_HYPERV_EDX] |= HV_FREQUENCY_MSRS_AVAILABLE; > } Since you have added

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Vitaly Kuznetsov
Roman Kagan writes: > On Tue, Mar 20, 2018 at 06:35:00PM +0100, Vitaly Kuznetsov wrote: >> Requiring tsc_is_stable_and_known() is too restrictive: even without INVTCS >> nested Hyper-V-on-KVM enables TSC pages for its guests e.g. when >> Reenlightenment MSRs are present.

Re: [Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-21 Thread Roman Kagan
On Tue, Mar 20, 2018 at 06:35:00PM +0100, Vitaly Kuznetsov wrote: > Requiring tsc_is_stable_and_known() is too restrictive: even without INVTCS > nested Hyper-V-on-KVM enables TSC pages for its guests e.g. when > Reenlightenment MSRs are present. Presence of frequency MSRs doesn't mean > these

[Qemu-devel] [PATCH v3 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

2018-03-20 Thread Vitaly Kuznetsov
Requiring tsc_is_stable_and_known() is too restrictive: even without INVTCS nested Hyper-V-on-KVM enables TSC pages for its guests e.g. when Reenlightenment MSRs are present. Presence of frequency MSRs doesn't mean these frequencies are stable, it just means they're available for reading.