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Subject[PATCH v2 2/3] KVM: X86: Provide a capability to disable cstate msr read intercepts
Date
From: Wanpeng Li <wanpengli@tencent.com>

Allow guest reads CORE cstate when exposing host CPU power management capabilities
to the guest. PKG cstate is restricted to avoid a guest to get the whole package
information in multi-tenant scenario.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
v1 -> v2:
* use a separate bit for KVM_CAP_X86_DISABLE_EXITS

Documentation/virtual/kvm/api.txt | 1 +
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/vmx/vmx.c | 6 ++++++
arch/x86/kvm/x86.c | 5 ++++-
arch/x86/kvm/x86.h | 5 +++++
include/uapi/linux/kvm.h | 4 +++-
tools/include/uapi/linux/kvm.h | 4 +++-
7 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 33cd92d..91fd86f 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4894,6 +4894,7 @@ Valid bits in args[0] are
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
+#define KVM_X86_DISABLE_EXITS_CSTATE (1 << 3)

Enabling this capability on a VM provides userspace with a way to no
longer intercept some instructions for improved latency in some
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d5457c7..1ce8289 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -882,6 +882,7 @@ struct kvm_arch {
bool mwait_in_guest;
bool hlt_in_guest;
bool pause_in_guest;
+ bool cstate_in_guest;

unsigned long irq_sources_bitmap;
s64 kvmclock_offset;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0861c71..da24f18 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6637,6 +6637,12 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_CS, MSR_TYPE_RW);
vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_ESP, MSR_TYPE_RW);
vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_EIP, MSR_TYPE_RW);
+ if (kvm_cstate_in_guest(kvm)) {
+ vmx_disable_intercept_for_msr(msr_bitmap, MSR_CORE_C1_RES, MSR_TYPE_R);
+ vmx_disable_intercept_for_msr(msr_bitmap, MSR_CORE_C3_RESIDENCY, MSR_TYPE_R);
+ vmx_disable_intercept_for_msr(msr_bitmap, MSR_CORE_C6_RESIDENCY, MSR_TYPE_R);
+ vmx_disable_intercept_for_msr(msr_bitmap, MSR_CORE_C7_RESIDENCY, MSR_TYPE_R);
+ }
vmx->msr_bitmap_mode = 0;

vmx->loaded_vmcs = &vmx->vmcs01;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 202048e..765fe59 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3098,7 +3098,8 @@ 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_HLT | KVM_X86_DISABLE_EXITS_PAUSE;
+ r |= KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_PAUSE |
+ KVM_X86_DISABLE_EXITS_CSTATE;
if(kvm_can_mwait_in_guest())
r |= KVM_X86_DISABLE_EXITS_MWAIT;
break;
@@ -4612,6 +4613,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
kvm->arch.hlt_in_guest = true;
if (cap->args[0] & KVM_X86_DISABLE_EXITS_PAUSE)
kvm->arch.pause_in_guest = true;
+ if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE)
+ kvm->arch.cstate_in_guest = true;
r = 0;
break;
case KVM_CAP_MSR_PLATFORM_INFO:
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index a470ff0..275b3b6 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -333,6 +333,11 @@ static inline bool kvm_pause_in_guest(struct kvm *kvm)
return kvm->arch.pause_in_guest;
}

+static inline bool kvm_cstate_in_guest(struct kvm *kvm)
+{
+ return kvm->arch.cstate_in_guest;
+}
+
DECLARE_PER_CPU(struct kvm_vcpu *, current_vcpu);

static inline void kvm_before_interrupt(struct kvm_vcpu *vcpu)
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 2fe12b4..c2152f3 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -696,9 +696,11 @@ struct kvm_ioeventfd {
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
+#define KVM_X86_DISABLE_EXITS_CSTATE (1 << 3)
#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT | \
KVM_X86_DISABLE_EXITS_HLT | \
- KVM_X86_DISABLE_EXITS_PAUSE)
+ KVM_X86_DISABLE_EXITS_PAUSE | \
+ KVM_X86_DISABLE_EXITS_CSTATE)

/* for KVM_ENABLE_CAP */
struct kvm_enable_cap {
diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
index 6d4ea4b..ef3303f 100644
--- a/tools/include/uapi/linux/kvm.h
+++ b/tools/include/uapi/linux/kvm.h
@@ -696,9 +696,11 @@ struct kvm_ioeventfd {
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
+#define KVM_X86_DISABLE_EXITS_CSTATE (1 << 3)
#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT | \
KVM_X86_DISABLE_EXITS_HLT | \
- KVM_X86_DISABLE_EXITS_PAUSE)
+ KVM_X86_DISABLE_EXITS_PAUSE | \
+ KVM_X86_DISABLE_EXITS_CSTATE)

/* for KVM_ENABLE_CAP */
struct kvm_enable_cap {
--
2.7.4
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