Messages in this thread | | | Date | Thu, 7 May 2009 15:55:22 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH][KVM] Add support for Pause Filtering to AMD SVM |
| |
Beside the small style problem the patch looks good. Please remove this empty line from the patch and resubmit. Please also add avi@redhat.com and kvm@vger.kernel.org to the CC list.
Joerg
On Tue, May 05, 2009 at 09:09:58AM -0500, Mark Langsdorf wrote: > commit 6f15c833f56267baf5abdd0fbc90a81489573053 > Author: Mark Langsdorf <mlangsdo@wshpnow.amd.com> > Date: Mon May 4 15:02:38 2009 -0500 > > New AMD processors will support the Pause Filter Feature. > This feature creates a new field in the VMCB called Pause > Filter Count. If Pause Filter Count is greater than 0 and > ntercepting PAUSEs is enabled, the processor will increment > an internal counter when a PAUSE instruction occurs instead > of intercepting. When the internal counter reaches the > Pause Filter Count value, a PAUSE intercept will occur. > > This feature can be used to detect contended spinlocks, > especially when the lock holding VCPU is not scheduled. > Rescheduling another VCPU prevents the VCPU seeking the > lock from wasting its quantum by spinning idly. > > Experimental results show that most spinlocks are held > for less than 1000 PAUSE cycles or more than a few > thousand. Default the Pause Filter Counter to 3000 to > detect the contended spinlocks. > > Processor support for this feature is indicated by a CPUID > bit. > > On a 24 core system running 4 guests each with 16 VCPUs, > this patch improved overall performance of each guest's > 32 job kernbench by approximately 1%. Further performance > improvement may be possible with a more sophisticated > yield algorithm. > > -Mark Langsdorf > Operating System Research Center > AMD > > Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com> > > diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h > index 85574b7..1fecb7e 100644 > --- a/arch/x86/include/asm/svm.h > +++ b/arch/x86/include/asm/svm.h > @@ -57,7 +57,8 @@ struct __attribute__ ((__packed__)) vmcb_control_area { > u16 intercept_dr_write; > u32 intercept_exceptions; > u64 intercept; > - u8 reserved_1[44]; > + u8 reserved_1[42]; > + u16 pause_filter_count; > u64 iopm_base_pa; > u64 msrpm_base_pa; > u64 tsc_offset; > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index ef43a18..14dab13 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -45,6 +45,7 @@ MODULE_LICENSE("GPL"); > #define SVM_FEATURE_NPT (1 << 0) > #define SVM_FEATURE_LBRV (1 << 1) > #define SVM_FEATURE_SVML (1 << 2) > +#define SVM_FEATURE_PAUSE_FILTER (1 << 10) > > #define DEBUGCTL_RESERVED_BITS (~(0x3fULL)) > > @@ -575,6 +576,12 @@ static void init_vmcb(struct vcpu_svm *svm) > > svm->nested_vmcb = 0; > svm->vcpu.arch.hflags = HF_GIF_MASK; > + > + if (svm_has(SVM_FEATURE_PAUSE_FILTER)) { > + control->pause_filter_count = 5000; > + control->intercept |= (1ULL << INTERCEPT_PAUSE); > + } > + > } > > static int svm_vcpu_reset(struct kvm_vcpu *vcpu) > @@ -2087,6 +2094,15 @@ static int interrupt_window_interception(struct vcpu_svm *svm, > return 1; > } > > +static int pause_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run) > +{ > + /* Simple yield */ > + vcpu_put(&svm->vcpu); > + schedule(); > + vcpu_load(&svm->vcpu); > + return 1; > +} > + > static int (*svm_exit_handlers[])(struct vcpu_svm *svm, > struct kvm_run *kvm_run) = { > [SVM_EXIT_READ_CR0] = emulate_on_interception, > @@ -2123,6 +2139,7 @@ static int (*svm_exit_handlers[])(struct vcpu_svm *svm, > [SVM_EXIT_CPUID] = cpuid_interception, > [SVM_EXIT_IRET] = iret_interception, > [SVM_EXIT_INVD] = emulate_on_interception, > + [SVM_EXIT_PAUSE] = pause_interception, > [SVM_EXIT_HLT] = halt_interception, > [SVM_EXIT_INVLPG] = invlpg_interception, > [SVM_EXIT_INVLPGA] = invalid_op_interception, > @@ -2227,6 +2244,7 @@ static void pre_svm_run(struct vcpu_svm *svm) > if (svm->vcpu.cpu != cpu || > svm->asid_generation != svm_data->asid_generation) > new_asid(svm, svm_data); > + > }
Minor style nit, please move this empty line from the patch.
> > static void svm_drop_interrupt_shadow(struct kvm_vcpu *vcpu) > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 2b73e19..e2b730d 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -710,6 +710,7 @@ void vcpu_load(struct kvm_vcpu *vcpu) > kvm_arch_vcpu_load(vcpu, cpu); > put_cpu(); > } > +EXPORT_SYMBOL_GPL(vcpu_load); > > void vcpu_put(struct kvm_vcpu *vcpu) > { > @@ -719,6 +720,7 @@ void vcpu_put(struct kvm_vcpu *vcpu) > preempt_enable(); > mutex_unlock(&vcpu->mutex); > } > +EXPORT_SYMBOL_GPL(vcpu_put); > > static void ack_flush(void *_completed) > {
-- | Advanced Micro Devices GmbH Operating | Karl-Hammerschmidt-Str. 34, 85609 Dornach bei München System | Research | Geschäftsführer: Thomas M. McCoy, Giuliano Meroni Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis München | Registergericht München, HRB Nr. 43632
-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |