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Commit 344c6c80 authored by Tianyu Lan's avatar Tianyu Lan Committed by Paolo Bonzini
Browse files

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: default avatarTianyu Lan <Tianyu.Lan@microsoft.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 7a83247e

Documentation/virt/kvm/api.txt

+13 −0
Original line number Diff line number Diff line
@@ -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.

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -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 {

arch/x86/kvm/x86.c

+8 −0
Original line number Diff line number Diff line
@@ -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;

include/uapi/linux/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -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