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Message-Id: <1520855584-10079-3-git-send-email-wanpengli@tencent.com>
Date: Mon, 12 Mar 2018 04:53:03 -0700
From: Wanpeng Li <kernellwp@...il.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Jan H . Schönherr <jschoenh@...zon.de>
Subject: [PATCH v2 2/3] KVM: X86: Provides userspace with a capability to not intercept HLT
From: Wanpeng Li <wanpengli@...cent.com>
If host CPUs are dedicated to a VM, we can avoid VM exits on HLT.
This patch adds the per-VM non-HLT-exiting capability.
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Jan H. Schönherr <jschoenh@...zon.de>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
Documentation/virtual/kvm/api.txt | 3 ++-
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/cpuid.c | 5 +++++
arch/x86/kvm/svm.c | 4 +++-
arch/x86/kvm/vmx.c | 24 ++++++++++++++++++++++++
arch/x86/kvm/x86.c | 3 +++
arch/x86/kvm/x86.h | 9 ++++++++-
7 files changed, 46 insertions(+), 3 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 76e5a15..b46494d 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4367,10 +4367,11 @@ Returns: 0 on success, -EINVAL when args[0] contains invalid exits
Valid exits in args[0] are
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
+#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
Enabling this capability on a VM provides userspace with a way to no
longer intercepts some instructions for improved latency in some
-workloads.
+workloads. Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
8. Other capabilities.
----------------------
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e107171..1a79065 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -812,6 +812,7 @@ struct kvm_arch {
gpa_t wall_clock;
bool mwait_in_guest;
+ bool hlt_in_guest;
bool ept_identity_pagetable_done;
gpa_t ept_identity_map_addr;
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e2d3050..82055b9 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -135,6 +135,11 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
return -EINVAL;
}
+ best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
+ if (kvm_hlt_in_guest(vcpu->kvm) && best &&
+ (best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
+ best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
+
/* Update physical-address width */
vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
kvm_mmu_reset_context(vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 321b3fd..0b2e7af 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1372,7 +1372,6 @@ 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);
@@ -1395,6 +1394,9 @@ static void init_vmcb(struct vcpu_svm *svm)
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));
control->int_ctl = V_INTR_MASKING_MASK;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2302ae2..fa0c5e1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2543,6 +2543,19 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit
return 0;
}
+static void vmx_clear_hlt(struct kvm_vcpu *vcpu)
+{
+ /*
+ * 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) &&
+ vmcs_read32(GUEST_ACTIVITY_STATE) == GUEST_ACTIVITY_HLT)
+ vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
+}
+
static void vmx_queue_exception(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -2573,6 +2586,8 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
intr_info |= INTR_TYPE_HARD_EXCEPTION;
vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
+
+ vmx_clear_hlt(vcpu);
}
static bool vmx_rdtscp_supported(void)
@@ -5532,6 +5547,8 @@ 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;
}
@@ -5893,6 +5910,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
update_exception_bitmap(vcpu);
vpid_sync_context(vmx->vpid);
+ if (init_event)
+ vmx_clear_hlt(vcpu);
}
/*
@@ -5963,6 +5982,8 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
} else
intr |= INTR_TYPE_EXT_INTR;
vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr);
+
+ vmx_clear_hlt(vcpu);
}
static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
@@ -5993,6 +6014,8 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR);
+
+ vmx_clear_hlt(vcpu);
}
static bool vmx_get_nmi_mask(struct kvm_vcpu *vcpu)
@@ -12314,6 +12337,7 @@ static int vmx_pre_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
vmx->nested.smm.vmxon = vmx->nested.vmxon;
vmx->nested.vmxon = false;
+ vmx_clear_hlt(vcpu);
return 0;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5fae476..73255e6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2874,6 +2874,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = KVM_CLOCK_TSC_STABLE;
break;
case KVM_CAP_X86_DISABLE_EXITS:
+ r |= KVM_X86_DISABLE_EXITS_HTL;
if(kvm_can_mwait_in_guest())
r |= KVM_X86_DISABLE_EXITS_MWAIT;
break;
@@ -4228,6 +4229,8 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) &&
kvm_can_mwait_in_guest())
kvm->arch.mwait_in_guest = true;
+ if (cap->args[0] & KVM_X86_DISABLE_EXITS_HTL)
+ kvm->arch.hlt_in_guest = true;
r = 0;
break;
default:
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index cd1215e..d4ddb00 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -263,11 +263,18 @@ static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec)
})
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
-#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT)
+#define KVM_X86_DISABLE_EXITS_HTL (1 << 1)
+#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT | \
+ KVM_X86_DISABLE_EXITS_HTL)
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
--
2.7.4
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