Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1598184
| From | Jim Mattson <jmattson@google.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] kvm: better MWAIT emulation for guests |
| Date | 2017-03-11 00:50 +0100 |
| Message-ID | <tjCsi-2Fo-7@gated-at.bofh.it> (permalink) |
| References | <tjeSZ-32y-13@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, Mar 9, 2017 at 2:29 PM, Michael S. Tsirkin <mst@redhat.com> wrote: > Some guests call mwait without checking the cpu flags. We currently "Some guests"? What guests other than Mac OS X are so ill-behaved? > emulate that as a NOP but on VMX we can do better: let guest stop the > CPU until timer or IPI. 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 you must halt if you want to go deep into sleep. Thus it isn't > a good idea to use the regular MWAIT flag in CPUID for that. Add a flag > in the hypervisor leaf instead. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > Documentation/virtual/kvm/cpuid.txt | 3 +++ > arch/x86/include/uapi/asm/kvm_para.h | 1 + > arch/x86/kvm/cpuid.c | 3 +++ > arch/x86/kvm/vmx.c | 4 ---- > 4 files changed, 7 insertions(+), 4 deletions(-) > > diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt > index 3c65feb..5caa234 100644 > --- a/Documentation/virtual/kvm/cpuid.txt > +++ b/Documentation/virtual/kvm/cpuid.txt > @@ -54,6 +54,9 @@ KVM_FEATURE_PV_UNHALT || 7 || guest checks this feature bit > || || before enabling paravirtualized > || || spinlock support. > ------------------------------------------------------------------------------ > +KVM_FEATURE_MWAIT || 8 || guest can use monitor/mwait > + || || to halt the VCPU. > +------------------------------------------------------------------------------ > KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side > || || per-cpu warps are expected in > || || kvmclock. > diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h > index cff0bb6..9cc77a7 100644 > --- a/arch/x86/include/uapi/asm/kvm_para.h > +++ b/arch/x86/include/uapi/asm/kvm_para.h > @@ -24,6 +24,7 @@ > #define KVM_FEATURE_STEAL_TIME 5 > #define KVM_FEATURE_PV_EOI 6 > #define KVM_FEATURE_PV_UNHALT 7 > +#define KVM_FEATURE_MWAIT 8 > > /* The last 8 bits are used to indicate how to interpret the flags field > * in pvclock structure. If no bits are set, all flags are ignored. > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index efde6cc..fe3d292 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -594,6 +594,9 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > if (sched_info_on()) > entry->eax |= (1 << KVM_FEATURE_STEAL_TIME); > > + if (this_cpu_has(X86_FEATURE_MWAIT)) > + entry->eax = (1 << KVM_FEATURE_MWAIT); > + > entry->ebx = 0; > entry->ecx = 0; > entry->edx = 0; > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 4bfe349..b167aba 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -3547,13 +3547,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf) > CPU_BASED_USE_IO_BITMAPS | > CPU_BASED_MOV_DR_EXITING | > CPU_BASED_USE_TSC_OFFSETING | > - CPU_BASED_MWAIT_EXITING | > - CPU_BASED_MONITOR_EXITING | > CPU_BASED_INVLPG_EXITING | > CPU_BASED_RDPMC_EXITING; > > - printk(KERN_ERR "cleared CPU_BASED_MWAIT_EXITING + CPU_BASED_MONITOR_EXITING\n"); > - > opt = CPU_BASED_TPR_SHADOW | > CPU_BASED_USE_MSR_BITMAPS | > CPU_BASED_ACTIVATE_SECONDARY_CONTROLS; > -- > MST
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-09 23:40 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-10 02:00 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-10 02:20 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests Wanpeng Li <kernellwp@gmail.com> - 2017-03-13 08:50 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests Jim Mattson <jmattson@google.com> - 2017-03-11 00:50 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-12 01:10 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests "Gabriel L. Somlo" <gsomlo@gmail.com> - 2017-03-12 22:20 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-13 16:50 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-13 17:10 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-13 20:40 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests "Michael S. Tsirkin" <mst@redhat.com> - 2017-03-13 21:10 +0100
Re: [PATCH] kvm: better MWAIT emulation for guests Radim Krčmář <rkrcmar@redhat.com> - 2017-03-13 22:50 +0100
csiph-web