[PATCH v2 1/3] KVM: x86: add support for user wait instructions

Tao Xu
2019-05-24T07:59:18Z

This patch adds support for UMONITOR, UMWAIT and TPAUSE instructions
in kvm, and by default dont't expose it to kvm and provide a capability
to enable it.

Co-developed-by: Jingqi Liu <jingqi.liu@intel.com>
Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
Signed-off-by: Tao Xu <tao3.xu@intel.com>
---
Documentation/virtual/kvm/api.txt | 12 ++++++++++++
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/include/asm/vmx.h | 1 +
arch/x86/kvm/cpuid.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 4 ++++
arch/x86/kvm/x86.c | 7 +++++++
arch/x86/kvm/x86.h | 5 +++++
include/uapi/linux/kvm.h | 1 +
8 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index ba6c42c576dd..3d0196220486 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4997,6 +4997,18 @@ it hard or impossible to use it correctly. The availability of
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 signals that those bugs are fixed.
Userspace should not try to use KVM_CAP_MANUAL_DIRTY_LOG_PROTECT.

+7.19 KVM_CAP_ENABLE_USR_WAIT_PAUSE
+
+Architectures: x86
+Parameters: args[0] whether feature should be enabled or not
+
+With this capability enabled, a VM can use UMONITOR, UMWAIT and TPAUSE
+instructions. If the instruction causes a delay, the amount of
+time delayed is called here the physical delay. The physical delay is
+first computed by determining the virtual delay (the time to delay
+relative to the VM’s timestamp counter). Otherwise, UMONITOR, UMWAIT
+and TPAUSE cause an invalid-opcode exception(#UD).
+
8. Other capabilities.
----------------------

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 450d69a1e6fa..0da87c2e1c4d 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 enable_usr_wait_pause;

unsigned long irq_sources_bitmap;
s64 kvmclock_offset;
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 4e4133e86484..1c94b1009288 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -82,6 +82,7 @@
#define SECONDARY_EXEC_PT_USE_GPA 0x01000000
#define SECONDARY_EXEC_MODE_BASED_EPT_EXEC 0x00400000
#define SECONDARY_EXEC_TSC_SCALING 0x02000000
+#define SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE 0x04000000

#define PIN_BASED_EXT_INTR_MASK 0x00000001
#define PIN_BASED_NMI_EXITING 0x00000008
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 80a642a0143d..1cc001870a9d 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -405,7 +405,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ |
F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
- F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B);
+ F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/;

/* cpuid 7.0.edx*/
const u32 kvm_cpuid_7_0_edx_x86_features =
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1ac167614032..a65ee7ea47b4 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2247,6 +2247,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
SECONDARY_EXEC_RDRAND_EXITING |
SECONDARY_EXEC_ENABLE_PML |
SECONDARY_EXEC_TSC_SCALING |
+ SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE |
SECONDARY_EXEC_PT_USE_GPA |
SECONDARY_EXEC_PT_CONCEAL_VMX |
SECONDARY_EXEC_ENABLE_VMFUNC |
@@ -3880,6 +3881,9 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
exec_control &= ~SECONDARY_EXEC_UNRESTRICTED_GUEST;
if (kvm_pause_in_guest(vmx->vcpu.kvm))
exec_control &= ~SECONDARY_EXEC_PAUSE_LOOP_EXITING;
+ if (!kvm_enable_usr_wait_pause(vmx->vcpu.kvm) ||
+ (vmcs_config.cpu_based_exec_ctrl & CPU_BASED_RDTSC_EXITING))
+ exec_control &= ~SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
if (!kvm_vcpu_apicv_active(vcpu))
exec_control &= ~(SECONDARY_EXEC_APIC_REGISTER_VIRT |
SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 536b78c4af6e..38a89c878c5d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3141,6 +3141,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = kvm_x86_ops->get_nested_state ?
kvm_x86_ops->get_nested_state(NULL, NULL, 0) : 0;
break;
+ case KVM_CAP_ENABLE_USR_WAIT_PAUSE:
+ r = boot_cpu_has(X86_FEATURE_WAITPKG);
+ break;
default:
break;
}
@@ -4622,6 +4625,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
kvm->arch.exception_payload_enabled = cap->args[0];
r = 0;
break;
+ case KVM_CAP_ENABLE_USR_WAIT_PAUSE:
+ kvm->arch.enable_usr_wait_pause = true;
+ r = 0;
+ break;
default:
r = -EINVAL;
break;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index a470ff0868c5..37685e6679f3 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_enable_usr_wait_pause(struct kvm *kvm)
+{
+ return kvm->arch.enable_usr_wait_pause;
+}
+
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 2fe12b40d503..5a19a5984c57 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -993,6 +993,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_ARM_SVE 170
#define KVM_CAP_ARM_PTRAUTH_ADDRESS 171
#define KVM_CAP_ARM_PTRAUTH_GENERIC 172
+#define KVM_CAP_ENABLE_USR_WAIT_PAUSE 173

#ifdef KVM_CAP_IRQ_ROUTING

--
2.20.1