From 344c6c804703841d2bff4d68d7390ba726053874 Mon Sep 17 00:00:00 2001 From: Tianyu Lan Date: Thu, 22 Aug 2019 22:30:20 +0800 Subject: [PATCH] KVM/Hyper-V: Add new KVM capability KVM_CAP_HYPERV_DIRECT_TLBFLUSH Hyper-V direct tlb flush function should be enabled for guest that only uses Hyper-V hypercall. User space hypervisor(e.g, Qemu) can disable KVM identification in CPUID and just exposes Hyper-V identification to make sure the precondition. Add new KVM capability KVM_CAP_ HYPERV_DIRECT_TLBFLUSH for user space to enable Hyper-V direct tlb function and this function is default to be disabled in KVM. Signed-off-by: Tianyu Lan Signed-off-by: Paolo Bonzini --- Documentation/virt/kvm/api.txt | 13 +++++++++++++ arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/x86.c | 8 ++++++++ include/uapi/linux/kvm.h | 1 + 4 files changed, 23 insertions(+) diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt index 136f1ee..4833904 100644 --- a/Documentation/virt/kvm/api.txt +++ b/Documentation/virt/kvm/api.txt @@ -5309,3 +5309,16 @@ Architectures: x86 This capability indicates that KVM supports paravirtualized Hyper-V IPI send hypercalls: HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx. +8.21 KVM_CAP_HYPERV_DIRECT_TLBFLUSH + +Architecture: x86 + +This capability indicates that KVM running on top of Hyper-V hypervisor +enables Direct TLB flush for its guests meaning that TLB flush +hypercalls are handled by Level 0 hypervisor (Hyper-V) bypassing KVM. +Due to the different ABI for hypercall parameters between Hyper-V and +KVM, enabling this capability effectively disables all hypercall +handling by KVM (as some KVM hypercall may be mistakenly treated as TLB +flush hypercalls by Hyper-V) so userspace should disable KVM identification +in CPUID and only exposes Hyper-V identification. In this case, guest +thinks it's running on Hyper-V and only use Hyper-V hypercalls. diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index a3a3ec7..4765ae0 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1213,6 +1213,7 @@ struct kvm_x86_ops { bool (*need_emulation_on_page_fault)(struct kvm_vcpu *vcpu); bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu); + int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu); }; struct kvm_arch_async_pf { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index bb93771..5becc67 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3282,6 +3282,9 @@ 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_HYPERV_DIRECT_TLBFLUSH: + r = kvm_x86_ops->enable_direct_tlbflush ? 1 : 0; + break; default: break; } @@ -4055,6 +4058,11 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu, r = -EFAULT; } return r; + case KVM_CAP_HYPERV_DIRECT_TLBFLUSH: + if (!kvm_x86_ops->enable_direct_tlbflush) + return -ENOTTY; + + return kvm_x86_ops->enable_direct_tlbflush(vcpu); default: return -EINVAL; diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 233efbb..c73aead 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -999,6 +999,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_ARM_PTRAUTH_GENERIC 172 #define KVM_CAP_PMU_EVENT_FILTER 173 #define KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 174 +#define KVM_CAP_HYPERV_DIRECT_TLBFLUSH 175 #ifdef KVM_CAP_IRQ_ROUTING -- 2.7.4