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KVM/Hyper-V: Add new KVM capability KVM_CAP_HYPERV_DIRECT_TLBFLUSH

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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 <Tianyu.Lan@microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Tianyu Lan 2019-08-22 22:30:20 +08:00 committed by Paolo Bonzini
parent 7a83247e01
commit 344c6c8047
4 changed files with 23 additions and 0 deletions
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13
Documentation/virt/kvm/api.txt
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@ -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.

1
arch/x86/include/asm/kvm_host.h
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@ -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 {

8
arch/x86/kvm/x86.c
View File

@ -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;

1
include/uapi/linux/kvm.h
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@ -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