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Groups > linux.kernel > #1601754 > unrolled thread
| Started by | "Michael S. Tsirkin" <mst@redhat.com> |
|---|---|
| First post | 2017-03-15 22:30 +0100 |
| Last post | 2017-03-27 15:40 +0200 |
| Articles | 3 on this page of 43 — 7 participants |
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[PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-15 22:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 00:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 00:50 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 14:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-16 15:10 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 17:00 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-16 17:00 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 17:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 15:10 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 16:00 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 16:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-16 16:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-16 17:10 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 17:50 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 18:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 18:50 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 19:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 20:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 21:20 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 22:20 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-17 03:10 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-17 14:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-21 04:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-21 18:10 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Nadav Amit <nadav.amit@gmail.com> - 2017-03-21 18:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-21 20:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Gabriel Somlo <gsomlo@gmail.com> - 2017-03-22 00:00 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Nadav Amit <nadav.amit@gmail.com> - 2017-03-22 01:10 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-22 14:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-22 15:20 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-22 15:20 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 20:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-16 18:30 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 18:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 17:20 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 17:50 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 18:00 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-16 18:00 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-16 18:20 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-16 18:40 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Joerg Roedel <joro@8bytes.org> - 2017-03-21 17:20 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-21 19:50 +0100
Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests Alexander Graf <agraf@suse.de> - 2017-03-27 15:40 +0200
Page 3 of 3 — ← Prev page 1 2 [3]
| From | Joerg Roedel <joro@8bytes.org> |
|---|---|
| Date | 2017-03-21 17:20 +0100 |
| Message-ID | <tnuFQ-5IV-37@gated-at.bofh.it> |
| In reply to | #1601754 |
On Wed, Mar 15, 2017 at 11:22:18PM +0200, Michael S. Tsirkin wrote: > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index d1efe2c..18e53bc 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -1198,8 +1198,6 @@ static void init_vmcb(struct vcpu_svm *svm) > set_intercept(svm, INTERCEPT_CLGI); > set_intercept(svm, INTERCEPT_SKINIT); > set_intercept(svm, INTERCEPT_WBINVD); > - set_intercept(svm, INTERCEPT_MONITOR); > - set_intercept(svm, INTERCEPT_MWAIT); Why do you remove the intercepts for AMD? The new kvm_mwait_in_guest() function will always return false on AMD anyway, and on Intel you re-add the intercepts for !kvm_mwait_in_guest(). Joerg
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| From | "Michael S. Tsirkin" <mst@redhat.com> |
|---|---|
| Date | 2017-03-21 19:50 +0100 |
| Message-ID | <tnx11-7bE-35@gated-at.bofh.it> |
| In reply to | #1605773 |
On Tue, Mar 21, 2017 at 05:16:32PM +0100, Joerg Roedel wrote: > On Wed, Mar 15, 2017 at 11:22:18PM +0200, Michael S. Tsirkin wrote: > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > > index d1efe2c..18e53bc 100644 > > --- a/arch/x86/kvm/svm.c > > +++ b/arch/x86/kvm/svm.c > > @@ -1198,8 +1198,6 @@ static void init_vmcb(struct vcpu_svm *svm) > > set_intercept(svm, INTERCEPT_CLGI); > > set_intercept(svm, INTERCEPT_SKINIT); > > set_intercept(svm, INTERCEPT_WBINVD); > > - set_intercept(svm, INTERCEPT_MONITOR); > > - set_intercept(svm, INTERCEPT_MWAIT); > > Why do you remove the intercepts for AMD? The new kvm_mwait_in_guest() > function will always return false on AMD anyway, I think that's a bug and I should fix it to return true there. > and on Intel you re-add > the intercepts for !kvm_mwait_in_guest(). > > > Joerg Does AMD need some work-around similar to CPUID5_ECX_INTERRUPT_BREAK? That's why we have kvm_mwait_in_guest ... -- MST
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| From | Alexander Graf <agraf@suse.de> |
|---|---|
| Date | 2017-03-27 15:40 +0200 |
| Message-ID | <tpD2h-kn-21@gated-at.bofh.it> |
| In reply to | #1601754 |
On 15/03/2017 22:22, Michael S. Tsirkin wrote: > Guests running Mac OS 5, 6, and 7 (Leopard through Lion) have a problem: > unless explicitly provided with kernel command line argument > "idlehalt=0" they'd implicitly assume MONITOR and MWAIT availability, > without checking CPUID. > > We currently emulate that as a NOP but on VMX we can do better: let > guest stop the CPU until timer, IPI or memory change. CPU will be busy > but that isn't any worse than a NOP emulation. > > Note that mwait within guests is not the same as on real hardware > because halt causes an exit while mwait doesn't. For this reason it > might not be a good idea to use the regular MWAIT flag in CPUID to > signal this capability. Add a flag in the hypervisor leaf instead. So imagine we had proper MWAIT emulation capabilities based on page faults. In that case, we could do something as fancy as Treat MWAIT as pass-through by default Have a per-vcpu monitor timer 10 times a second in the background that checks which instruction we're in If we're in mwait for the last - say - 1 second, switch to emulated MWAIT, if $IP was in non-mwait within that time, reset counter. Or instead maybe just reuse the adapter hlt logic? Either way, with that we should be able to get super low latency IPIs running while still maintaining some sanity on systems which don't have dedicated CPUs for workloads. And we wouldn't need guest modifications, which is a great plus. So older guests (and Windows?) could benefit from mwait as well. Alex
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