Re: [PATCH v3 9/9] kvm/x86: Hyper-V kvm exit

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On 11/03/2015 04:28 PM, Paolo Bonzini wrote:


On 22/10/2015 18:10, Andrey Smetanin wrote:
A new vcpu exit is introduced to notify the userspace of the
changes in Hyper-V SynIC configuration triggered by guest writing to the
corresponding MSRs.

Changes v3:
* added KVM_EXIT_HYPERV types and structs notes into docs

Signed-off-by: Andrey Smetanin <asmetanin@xxxxxxxxxxxxx>
Reviewed-by: Roman Kagan <rkagan@xxxxxxxxxxxxx>
Signed-off-by: Denis V. Lunev <den@xxxxxxxxxx>
CC: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
CC: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
CC: Gleb Natapov <gleb@xxxxxxxxxx>
CC: Paolo Bonzini <pbonzini@xxxxxxxxxx>
CC: Roman Kagan <rkagan@xxxxxxxxxxxxx>

---
  Documentation/virtual/kvm/api.txt | 22 ++++++++++++++++++++++
  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, 64 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 8710418..a6858eb 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3337,6 +3337,28 @@ 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.

+		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;
+		};
+		/* KVM_EXIT_HYPERV */
+                struct kvm_hyperv_exit hyperv;
+Indicates that the VCPU exits into userspace to process some tasks
+related to Hyper-V emulation.
+Valid values for 'type' are:
+	KVM_EXIT_HYPERV_SYNIC -- synchronously notify user-space about
+Hyper-V SynIC state change. Notification is used to remap SynIC
+event/message pages and to enable/disable SynIC messages/events processing
+in 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 8434f88..54c90d3 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 8ff71f3..9443920 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -129,6 +129,20 @@ static void kvm_hv_notify_acked_sint(struct kvm_vcpu *vcpu, u32 sint)
  	srcu_read_unlock(&kvm->irq_srcu, idx);
  }

+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)
  {
@@ -141,6 +155,7 @@ 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);

Another note.  I am getting:

EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000663
ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =f000 ffff0000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300
DS =0000 00000000 0000ffff 00009300
FS =0000 00000000 0000ffff 00009300
GS =0000 00000000 0000ffff 00009300
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     00000000 0000ffff
IDT=     00000000 0000ffff
CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000
DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000000
Code=90 90 90 90 eb c3 90 90 90 90 90 90 00 00 00 00 56 54 46 00 <90> 90
eb ac 90 90 90 90 90 90 90 90 90 90 90 90 00 00 00 00 00 00 00 00 00 00
00 00 00 00

if I run a patched QEMU but I *do not* enable the synthetic interrupt
controller.  I can fix it by wrapping the calls to synic_exit with "if
(!host)", but I haven't checked yet the source---so that may not be the
proper fix.  Sorry for not having looked more in detail.

Paolo

Thank you, we will test and resend correct version.
  		break;
  	case HV_X64_MSR_SVERSION:
  		if (!host) {
@@ -157,6 +172,7 @@ 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)
@@ -166,6 +182,7 @@ 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 b853b2df..0704ee3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6342,6 +6342,12 @@ 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 43b0141..e38ac16 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];
  	};

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