From: Tianyu Lan <Tianyu.Lan@microsoft.com>
Date: Thu, 22 Aug 2019 22:30:20 +0800
Patch-mainline: v5.4-rc1
Subject: KVM/Hyper-V: Add new KVM capability KVM_CAP_HYPERV_DIRECT_TLBFLUSH
Git-commit: 344c6c804703841d2bff4d68d7390ba726053874
References: fate#323887
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>
Acked-by: Olaf Hering <ohering@suse.de>
---
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(+)
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -5302,3 +5302,16 @@ 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.
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1211,6 +1211,7 @@ struct kvm_x86_ops {
uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);
bool (*need_emulation_on_page_fault)(struct kvm_vcpu *vcpu);
+ int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu);
};
struct kvm_arch_async_pf {
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3188,6 +3188,9 @@ int kvm_vm_ioctl_check_extension(struct
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;
}
@@ -3962,6 +3965,11 @@ static int kvm_vcpu_ioctl_enable_cap(str
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;
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -997,6 +997,7 @@ 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