From: Andrey Smetanin <asmeta...@virtuozzo.com>

A new vcpu exit is introduced to notify the userspace of the
changes in Hyper-V synic configuraion triggered by guest writing to the
corresponding MSRs.

Signed-off-by: Andrey Smetanin <asmeta...@virtuozzo.com>
Reviewed-by: Roman Kagan <rka...@virtiozzo.com>
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Vitaly Kuznetsov <vkuzn...@redhat.com>
CC: "K. Y. Srinivasan" <k...@microsoft.com>
CC: Gleb Natapov <g...@kernel.org>
CC: Paolo Bonzini <pbonz...@redhat.com>
---
 Documentation/virtual/kvm/api.txt |  6 ++++++
 arch/x86/include/asm/kvm_host.h   |  1 +
 arch/x86/kvm/hyperv.c             | 17 +++++++++++++++++
 arch/x86/kvm/x86.c                |  6 ++++++
 include/linux/kvm_host.h          |  1 +
 include/uapi/linux/kvm.h          | 17 +++++++++++++++++
 6 files changed, 48 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt 
b/Documentation/virtual/kvm/api.txt
index 34cc068..cffe670 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3331,6 +3331,12 @@ the userspace IOAPIC should process the EOI and 
retrigger the interrupt if
 it is still asserted.  Vector is the LAPIC interrupt vector for which the
 EOI was received.
 
+               /* KVM_EXIT_HYPERV */
+                struct kvm_hyperv_exit hyperv;
+Indicates that the VCPU's exits into userspace to process some tasks
+related with Hyper-V emulation. Currently used to synchronize modified
+Hyper-V synic state with userspace.
+
                /* Fix the size of the union. */
                char padding[256];
        };
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e614a543..f515e01 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -392,6 +392,7 @@ struct kvm_vcpu_hv {
        u64 hv_vapic;
        s64 runtime_offset;
        struct kvm_vcpu_hv_synic synic;
+       struct kvm_hyperv_exit exit;
 };
 
 struct kvm_vcpu_arch {
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 15c3c02..174ce041 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -91,6 +91,20 @@ static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, 
int sint, u64 data)
        return 0;
 }
 
+static void synic_exit(struct kvm_vcpu_hv_synic *synic, u32 msr)
+{
+       struct kvm_vcpu *vcpu = synic_to_vcpu(synic);
+       struct kvm_vcpu_hv *hv_vcpu = &vcpu->arch.hyperv;
+
+       hv_vcpu->exit.type = KVM_EXIT_HYPERV_SYNIC;
+       hv_vcpu->exit.u.synic.msr = msr;
+       hv_vcpu->exit.u.synic.control = synic->control;
+       hv_vcpu->exit.u.synic.evt_page = synic->evt_page;
+       hv_vcpu->exit.u.synic.msg_page = synic->msg_page;
+
+       kvm_make_request(KVM_REQ_HV_EXIT, vcpu);
+}
+
 static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
                         u32 msr, u64 data, bool host)
 {
@@ -103,6 +117,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
        switch (msr) {
        case HV_X64_MSR_SCONTROL:
                synic->control = data;
+               synic_exit(synic, msr);
                break;
        case HV_X64_MSR_SVERSION:
                if (!host) {
@@ -119,6 +134,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
                                break;
                        }
                synic->evt_page = data;
+               synic_exit(synic, msr);
                break;
        case HV_X64_MSR_SIMP:
                if (data & HV_SYNIC_SIMP_ENABLE)
@@ -128,6 +144,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
                                break;
                        }
                synic->msg_page = data;
+               synic_exit(synic, msr);
                break;
        case HV_X64_MSR_EOM: {
                int i;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7580e9c..4c80d18 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6335,6 +6335,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
                        r = 0;
                        goto out;
                }
+               if (kvm_check_request(KVM_REQ_HV_EXIT, vcpu)) {
+                       vcpu->run->exit_reason = KVM_EXIT_HYPERV;
+                       vcpu->run->hyperv = vcpu->arch.hyperv.exit;
+                       r = 0;
+                       goto out;
+               }
        }
 
        /*
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 30fac73..d80b031 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -143,6 +143,7 @@ static inline bool is_error_page(struct page *page)
 #define KVM_REQ_HV_CRASH          27
 #define KVM_REQ_IOAPIC_EOI_EXIT   28
 #define KVM_REQ_HV_RESET          29
+#define KVM_REQ_HV_EXIT           30
 
 #define KVM_USERSPACE_IRQ_SOURCE_ID            0
 #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID       1
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 27ce460..6e32f75 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -154,6 +154,20 @@ struct kvm_s390_skeys {
        __u32 flags;
        __u32 reserved[9];
 };
+
+struct kvm_hyperv_exit {
+#define KVM_EXIT_HYPERV_SYNIC          1
+       __u32 type;
+       union {
+               struct {
+                       __u32 msr;
+                       __u64 control;
+                       __u64 evt_page;
+                       __u64 msg_page;
+               } synic;
+       } u;
+};
+
 #define KVM_S390_GET_SKEYS_NONE   1
 #define KVM_S390_SKEYS_MAX        1048576
 
@@ -184,6 +198,7 @@ struct kvm_s390_skeys {
 #define KVM_EXIT_SYSTEM_EVENT     24
 #define KVM_EXIT_S390_STSI        25
 #define KVM_EXIT_IOAPIC_EOI       26
+#define KVM_EXIT_HYPERV           27
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
@@ -338,6 +353,8 @@ struct kvm_run {
                struct {
                        __u8 vector;
                } eoi;
+               /* KVM_EXIT_HYPERV */
+               struct kvm_hyperv_exit hyperv;
                /* Fix the size of the union. */
                char padding[256];
        };
-- 
2.1.4

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