2017-11-25 21:09 GMT+08:00 Jan H. Schönherr <jschoenh@xxxxxxxxx>:
> If host CPUs are dedicated to a VM, we can avoid VM exits on HLT,
> reducing the wake-up latency on posted interrupts.
>
> This reintroduces a feature that has been there at some point --
> see Linux 3.4 commit 10166744b80a ("KVM: VMX: remove yield_on_hlt")
> for the removal -- but with the additional ability to enable it only
> for selected VMs (and supporting SVM as well).
>
> Signed-off-by: Jan H. Schönherr <jschoenh@xxxxxxxxx>
This patch results in guest hang during boot. Just the same when I
tried to avoid VM exits on HLT several months ago.
http://www.spinics.net/lists/kvm/msg152397.html
Regards,
Wanpeng Li
> ---
> Note: AMD code paths are only compile tested
> ---
> Documentation/virtual/kvm/api.txt | 12 +++++++++++-
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/svm.c | 3 ++-
> arch/x86/kvm/vmx.c | 33 +++++++++++++++++++++++++++------
> arch/x86/kvm/x86.c | 5 +++++
> arch/x86/kvm/x86.h | 5 +++++
> include/uapi/linux/kvm.h | 1 +
> 7 files changed, 52 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 0ee812c..c06bb41 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -4172,7 +4172,17 @@ Returns: 0 on success
> This capability indicates that a guest using memory monitoring instructions
> (MWAIT/MWAITX) to stop a virtual CPU will not cause a VM exit. As such, time
> spent while a virtual CPU is halted in this way will then be accounted for as
> -guest running time on the host (as opposed to e.g. HLT).
> +guest running time on the host.
> +
> +7.14 KVM_CAP_X86_GUEST_HLT
> +
> +Architectures: x86
> +Parameters: none
> +Returns: 0 on success
> +
> +This capability indicates that a guest using HLT to stop a virtual CPU will not
> +cause a VM exit. As such, time spent while a virtual CPU is halted in this way
> +will then be accounted for as guest running time on the host.
>
> 8. Other capabilities.
> ----------------------
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index f7bcfaa..3197c2d 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -781,6 +781,7 @@ struct kvm_arch {
>
> gpa_t wall_clock;
>
> + bool hlt_in_guest;
> bool mwait_in_guest;
>
> bool ept_identity_pagetable_done;
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index ef1b320..c135b98 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1236,7 +1236,6 @@ static void init_vmcb(struct vcpu_svm *svm)
> set_intercept(svm, INTERCEPT_RDPMC);
> set_intercept(svm, INTERCEPT_CPUID);
> set_intercept(svm, INTERCEPT_INVD);
> - set_intercept(svm, INTERCEPT_HLT);
> set_intercept(svm, INTERCEPT_INVLPG);
> set_intercept(svm, INTERCEPT_INVLPGA);
> set_intercept(svm, INTERCEPT_IOIO_PROT);
> @@ -1257,6 +1256,8 @@ static void init_vmcb(struct vcpu_svm *svm)
> set_intercept(svm, INTERCEPT_MONITOR);
> set_intercept(svm, INTERCEPT_MWAIT);
> }
> + if (!kvm_hlt_in_guest(svm->vcpu.kvm))
> + set_intercept(svm, INTERCEPT_HLT);
>
> control->iopm_base_pa = __sme_set(iopm_base);
> control->msrpm_base_pa = __sme_set(__pa(svm->msrpm));
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index a067735..1b67433 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2446,6 +2446,25 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
> vmx_set_interrupt_shadow(vcpu, 0);
> }
>
> +static void vmx_set_intr_info(struct kvm_vcpu *vcpu, u32 intr)
> +{
> + vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr);
> +
> + /*
> + * Ensure that we clear the HLT state in the VMCS. We don't need to
> + * explicitly skip the instruction because if the HLT state is set, then
> + * the instruction is already executing and RIP has already been
> + * advanced.
> + */
> + if (!kvm_hlt_in_guest(vcpu->kvm) || !(intr & INTR_INFO_VALID_MASK))
> + return;
> + if (is_external_interrupt(intr) || is_nmi(intr))
> + return;
> + if (vmcs_read32(GUEST_ACTIVITY_STATE) != GUEST_ACTIVITY_HLT)
> + return;
> + vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
> +}
> +
> static void nested_vmx_inject_exception_vmexit(struct kvm_vcpu *vcpu,
> unsigned long exit_qual)
> {
> @@ -2540,7 +2559,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
> } else
> intr_info |= INTR_TYPE_HARD_EXCEPTION;
>
> - vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
> + vmx_set_intr_info(vcpu, intr_info);
> }
>
> static bool vmx_rdtscp_supported(void)
> @@ -5298,6 +5317,8 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx)
> if (kvm_mwait_in_guest(vmx->vcpu.kvm))
> exec_control &= ~(CPU_BASED_MWAIT_EXITING |
> CPU_BASED_MONITOR_EXITING);
> + if (kvm_hlt_in_guest(vmx->vcpu.kvm))
> + exec_control &= ~CPU_BASED_HLT_EXITING;
> return exec_control;
> }
>
> @@ -5635,7 +5656,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>
> setup_msrs(vmx);
>
> - vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0); /* 22.2.1 */
> + vmx_set_intr_info(vcpu, 0); /* 22.2.1 */
>
> if (cpu_has_vmx_tpr_shadow() && !init_event) {
> vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, 0);
> @@ -5729,7 +5750,7 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
> vmx->vcpu.arch.event_exit_inst_len);
> } else
> intr |= INTR_TYPE_EXT_INTR;
> - vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr);
> + vmx_set_intr_info(vcpu, intr);
> }
>
> static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
> @@ -5758,8 +5779,8 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
> return;
> }
>
> - vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
> - INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR);
> + vmx_set_intr_info(vcpu, INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK |
> + NMI_VECTOR);
> }
>
> static bool vmx_get_nmi_mask(struct kvm_vcpu *vcpu)
> @@ -9301,7 +9322,7 @@ static void vmx_cancel_injection(struct kvm_vcpu *vcpu)
> VM_ENTRY_INSTRUCTION_LEN,
> VM_ENTRY_EXCEPTION_ERROR_CODE);
>
> - vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0);
> + vmx_set_intr_info(vcpu, 0);
> }
>
> static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fe6627a..f17c520 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2755,6 +2755,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_SET_BOOT_CPU_ID:
> case KVM_CAP_SPLIT_IRQCHIP:
> case KVM_CAP_IMMEDIATE_EXIT:
> + case KVM_CAP_X86_GUEST_HLT:
> r = 1;
> break;
> case KVM_CAP_ADJUST_CLOCK:
> @@ -4068,6 +4069,10 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
> r = 0;
> }
> break;
> + case KVM_CAP_X86_GUEST_HLT:
> + kvm->arch.hlt_in_guest = true;
> + r = 0;
> + break;
> default:
> r = -EINVAL;
> break;
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index ed8e150..b2066aa 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -266,4 +266,9 @@ static inline bool kvm_mwait_in_guest(struct kvm *kvm)
> return kvm->arch.mwait_in_guest;
> }
>
> +static inline bool kvm_hlt_in_guest(struct kvm *kvm)
> +{
> + return kvm->arch.hlt_in_guest;
> +}
> +
> #endif
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 282d7613..ff8f266 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -932,6 +932,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_HYPERV_SYNIC2 148
> #define KVM_CAP_HYPERV_VP_INDEX 149
> #define KVM_CAP_S390_AIS_MIGRATION 150
> +#define KVM_CAP_X86_GUEST_HLT 151
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> --
> 2.3.1.dirty
>
