Hi Jim, 2018-03-14 2:21 GMT+08:00 Jim Mattson <jmattson@xxxxxxxxxx>: > Is there a need for a new API for yielding MONITOR/MWAIT to the guest? > Why not just tie this to the guest CPUID.01H:ECX[MWAIT] being set? The API also will be used by HLT/PAUSE. Please refer to Paolo's original proposal though I didn't find a link which is replied by Paolo direclty. https://marc.info/?l=kvm&m=151182818103804&w=2 Regards, Wanpeng Li > > On Mon, Mar 12, 2018 at 4:53 AM, Wanpeng Li <kernellwp@xxxxxxxxx> wrote: >> From: Wanpeng Li <wanpengli@xxxxxxxxxxx> >> >> 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 <pbonzini@xxxxxxxxxx> >> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> >> Cc: Jan H. Schönherr <jschoenh@xxxxxxxxx> >> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx> >> --- >> 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 >>
