From: Wanpeng Li <[email protected]> Allowing a guest to execute MWAIT without interception enables a guest to put a (physical) CPU into a power saving state, where it takes longer to return from than what may be desired by the host.
Don't give a guest that power over a host by default. (Especially, since nothing prevents a guest from using MWAIT even when it is not advertised via CPUID.) Cc: Paolo Bonzini <[email protected]> Cc: Radim Krčmář <[email protected]> Cc: Jan H. Schönherr <[email protected]> Signed-off-by: Wanpeng Li <[email protected]> --- Documentation/virtual/kvm/api.txt | 23 ++++++++++++++--------- arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/svm.c | 2 +- arch/x86/kvm/vmx.c | 9 +++++---- arch/x86/kvm/x86.c | 24 ++++++++++++++++++++---- arch/x86/kvm/x86.h | 10 +++++----- include/uapi/linux/kvm.h | 2 +- tools/include/uapi/linux/kvm.h | 2 +- 8 files changed, 49 insertions(+), 25 deletions(-) diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 98de506..76e5a15 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -4358,6 +4358,20 @@ enables QEMU to build error log and branch to guest kernel registered machine check handling routine. Without this capability KVM will branch to guests' 0x200 interrupt vector. +7.13 KVM_CAP_X86_DISABLE_EXITS + +Architectures: x86 +Parameters: args[0] defines which exits are disabled +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) + +Enabling this capability on a VM provides userspace with a way to no +longer intercepts some instructions for improved latency in some +workloads. + 8. Other capabilities. ---------------------- @@ -4470,15 +4484,6 @@ reserved. Both registers and addresses are 64-bits wide. It will be possible to run 64-bit or 32-bit guest code. -8.8 KVM_CAP_X86_GUEST_MWAIT - -Architectures: x86 - -This capability indicates that guest using memory monotoring instructions -(MWAIT/MWAITX) to stop the virtual CPU will not cause a VM exit. As such time -spent while 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). - 8.9 KVM_CAP_ARM_USER_IRQ Architectures: arm, arm64 diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 0395c35..e107171 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -811,6 +811,8 @@ struct kvm_arch { gpa_t wall_clock; + bool mwait_in_guest; + bool ept_identity_pagetable_done; gpa_t ept_identity_map_addr; diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index be9c839..321b3fd 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1390,7 +1390,7 @@ static void init_vmcb(struct vcpu_svm *svm) set_intercept(svm, INTERCEPT_XSETBV); set_intercept(svm, INTERCEPT_RSM); - if (!kvm_mwait_in_guest()) { + if (!kvm_mwait_in_guest(svm->vcpu.kvm)) { set_intercept(svm, INTERCEPT_MONITOR); set_intercept(svm, INTERCEPT_MWAIT); } diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 6cefd7b..2302ae2 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3733,13 +3733,11 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf) CPU_BASED_UNCOND_IO_EXITING | CPU_BASED_MOV_DR_EXITING | CPU_BASED_USE_TSC_OFFSETING | + CPU_BASED_MWAIT_EXITING | + CPU_BASED_MONITOR_EXITING | CPU_BASED_INVLPG_EXITING | CPU_BASED_RDPMC_EXITING; - if (!kvm_mwait_in_guest()) - min |= CPU_BASED_MWAIT_EXITING | - CPU_BASED_MONITOR_EXITING; - opt = CPU_BASED_TPR_SHADOW | CPU_BASED_USE_MSR_BITMAPS | CPU_BASED_ACTIVATE_SECONDARY_CONTROLS; @@ -5531,6 +5529,9 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx) exec_control |= CPU_BASED_CR3_STORE_EXITING | CPU_BASED_CR3_LOAD_EXITING | CPU_BASED_INVLPG_EXITING; + if (kvm_mwait_in_guest(vmx->vcpu.kvm)) + exec_control &= ~(CPU_BASED_MWAIT_EXITING | + CPU_BASED_MONITOR_EXITING); return exec_control; } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 36ef3d8..5fae476 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2809,9 +2809,15 @@ static int msr_io(struct kvm_vcpu *vcpu, struct kvm_msrs __user *user_msrs, return r; } +static inline bool kvm_can_mwait_in_guest(void) +{ + return boot_cpu_has(X86_FEATURE_MWAIT) && + !boot_cpu_has_bug(X86_BUG_MONITOR); +} + int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) { - int r; + int r = 0; switch (ext) { case KVM_CAP_IRQCHIP: @@ -2867,8 +2873,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_ADJUST_CLOCK: r = KVM_CLOCK_TSC_STABLE; break; - case KVM_CAP_X86_GUEST_MWAIT: - r = kvm_mwait_in_guest(); + case KVM_CAP_X86_DISABLE_EXITS: + if(kvm_can_mwait_in_guest()) + r |= KVM_X86_DISABLE_EXITS_MWAIT; break; case KVM_CAP_X86_SMM: /* SMBASE is usually relocated above 1M on modern chipsets, @@ -2909,7 +2916,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_X2APIC_API_VALID_FLAGS; break; default: - r = 0; break; } return r; @@ -4214,6 +4220,16 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, r = 0; break; + case KVM_CAP_X86_DISABLE_EXITS: + r = -EINVAL; + if (cap->args[0] & ~KVM_X86_DISABLE_VALID_EXITS) + break; + + if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) && + kvm_can_mwait_in_guest()) + kvm->arch.mwait_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 b91215d..cd1215e 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -2,8 +2,6 @@ #ifndef ARCH_X86_KVM_X86_H #define ARCH_X86_KVM_X86_H -#include <asm/processor.h> -#include <asm/mwait.h> #include <linux/kvm_host.h> #include <asm/pvclock.h> #include "kvm_cache_regs.h" @@ -264,10 +262,12 @@ static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec) __rem; \ }) -static inline bool kvm_mwait_in_guest(void) +#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0) +#define KVM_X86_DISABLE_VALID_EXITS (KVM_X86_DISABLE_EXITS_MWAIT) + +static inline bool kvm_mwait_in_guest(struct kvm *kvm) { - return boot_cpu_has(X86_FEATURE_MWAIT) && - !boot_cpu_has_bug(X86_BUG_MONITOR); + return kvm->arch.mwait_in_guest; } #endif diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 088c2c9..1065006 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -929,7 +929,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_S390_GS 140 #define KVM_CAP_S390_AIS 141 #define KVM_CAP_SPAPR_TCE_VFIO 142 -#define KVM_CAP_X86_GUEST_MWAIT 143 +#define KVM_CAP_X86_DISABLE_EXITS 143 #define KVM_CAP_ARM_USER_IRQ 144 #define KVM_CAP_S390_CMMA_MIGRATION 145 #define KVM_CAP_PPC_FWNMI 146 diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h index 0fb5ef9..b13c257 100644 --- a/tools/include/uapi/linux/kvm.h +++ b/tools/include/uapi/linux/kvm.h @@ -924,7 +924,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_S390_GS 140 #define KVM_CAP_S390_AIS 141 #define KVM_CAP_SPAPR_TCE_VFIO 142 -#define KVM_CAP_X86_GUEST_MWAIT 143 +#define KVM_CAP_X86_DISABLE_EXITS 143 #define KVM_CAP_ARM_USER_IRQ 144 #define KVM_CAP_S390_CMMA_MIGRATION 145 #define KVM_CAP_PPC_FWNMI 146 -- 2.7.4
