>From a8e75742293c1c400dd5aa1d111825046cf26ab2 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 10 Jan 2022 12:40:31 -0800 Subject: [PATCH] KVM: x86: Let userspace re-enable previously disabled exits Add an OVERRIDE flag to KVM_CAP_X86_DISABLE_EXITS allow userspace to re-enable exits and/or override previous settings. There's no real use case for the the per-VM ioctl, but a future per-vCPU variant wants to let userspace toggle interception while the vCPU is running; add the OVERRIDE functionality now to provide consistent between between the per-VM and per-vCPU variants. Signed-off-by: Sean Christopherson --- Documentation/virt/kvm/api.rst | 5 +++++ arch/x86/kvm/x86.c | 37 +++++++++++++++++++++++----------- include/uapi/linux/kvm.h | 4 +++- 3 files changed, 33 insertions(+), 13 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 9460941d38d7..c42e653891a2 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6617,6 +6617,7 @@ Valid bits in args[0] are:: #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_EXITS_OVERRIDE (1ull << 63) Enabling this capability on a VM provides userspace with a way to no longer intercept some instructions for improved latency in some @@ -6625,6 +6626,10 @@ physical CPUs. More bits can be added in the future; userspace can just pass the KVM_CHECK_EXTENSION result to KVM_ENABLE_CAP to disable all such vmexits. +By default, this capability only disables exits. To re-enable an exit, or to +override previous settings, userspace can set KVM_X86_DISABLE_EXITS_OVERRIDE, +in which case KVM will enable/disable according to the mask (a '1' == disable). + Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits. 7.14 KVM_CAP_S390_HPAGE_1M diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7741a5980334..f611a49ceba4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4089,11 +4089,10 @@ static inline bool kvm_can_mwait_in_guest(void) static u64 kvm_get_allowed_disable_exits(void) { - u64 r = KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_PAUSE | - KVM_X86_DISABLE_EXITS_CSTATE; + u64 r = KVM_X86_DISABLE_VALID_EXITS; - if(kvm_can_mwait_in_guest()) - r |= KVM_X86_DISABLE_EXITS_MWAIT; + if (!kvm_can_mwait_in_guest()) + r &= ~KVM_X86_DISABLE_EXITS_MWAIT; return r; } @@ -5051,6 +5050,26 @@ static int kvm_vcpu_ioctl_device_attr(struct kvm_vcpu *vcpu, return r; } + +#define kvm_ioctl_disable_exits(a, mask) \ +({ \ + if ((mask) & KVM_X86_DISABLE_EXITS_OVERRIDE) { \ + (a).mwait_in_guest = (mask) & KVM_X86_DISABLE_EXITS_MWAIT; \ + (a).hlt_in_guest = (mask) & KVM_X86_DISABLE_EXITS_HLT; \ + (a).pause_in_guest = (mask) & KVM_X86_DISABLE_EXITS_PAUSE; \ + (a).cstate_in_guest = (mask) & KVM_X86_DISABLE_EXITS_CSTATE; \ + } else { \ + if ((mask) & KVM_X86_DISABLE_EXITS_MWAIT) \ + (a).mwait_in_guest = true; \ + if ((mask) & KVM_X86_DISABLE_EXITS_HLT) \ + (a).hlt_in_guest = true; \ + if ((mask) & KVM_X86_DISABLE_EXITS_PAUSE) \ + (a).pause_in_guest = true; \ + if ((mask) & KVM_X86_DISABLE_EXITS_CSTATE) \ + (a).cstate_in_guest = true; \ + } \ +}) + static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu, struct kvm_enable_cap *cap) { @@ -5794,14 +5813,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, if (kvm->created_vcpus) goto disable_exits_unlock; - if (cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) - kvm->arch.mwait_in_guest = true; - if (cap->args[0] & KVM_X86_DISABLE_EXITS_HLT) - 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; + kvm_ioctl_disable_exits(kvm->arch, cap->args[0]); + r = 0; disable_exits_unlock: mutex_unlock(&kvm->lock); diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index fbfd70d965c6..5e0ffc87a578 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -798,10 +798,12 @@ struct kvm_ioeventfd { #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_EXITS_OVERRIDE (1ull << 63) #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_CSTATE) + KVM_X86_DISABLE_EXITS_CSTATE | \ + KVM_X86_DISABLE_EXITS_OVERRIDE) /* for KVM_ENABLE_CAP */ struct kvm_enable_cap { -- 2.34.1.575.g55b058a8bb-goog