[PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Andrey Smetanin]

The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
for Hyper-V VMBus hypercalls(postmsg, signalevent)
to handle these hypercalls by QEMU.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org

Andrey Smetanin (5):
  kvm/x86: Rename Hyper-V long spin wait hypercall
  drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
  kvm/x86: Pass return code of kvm_emulate_hypercall
  kvm/x86: Hyper-V VMBus hypercall userspace exit
  kvm/x86: Reject Hyper-V hypercall continuation

 Documentation/virtual/kvm/api.txt  |  8 ++++++++
 arch/x86/include/uapi/asm/hyperv.h |  4 +++-
 arch/x86/kvm/hyperv.c              | 39 +++++++++++++++++++++++++++++---------
 arch/x86/kvm/hyperv.h              |  1 +
 arch/x86/kvm/svm.c                 |  3 +--
 arch/x86/kvm/vmx.c                 |  3 +--
 arch/x86/kvm/x86.c                 |  3 +++
 drivers/hv/hv.c                    |  5 +++--
 drivers/hv/hyperv_vmbus.h          |  6 ------
 include/uapi/linux/kvm.h           |  7 +++++++
 10 files changed, 57 insertions(+), 22 deletions(-)

-- 
2.4.3

[Qemu-devel] [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Andrey Smetanin]

The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
for Hyper-V VMBus hypercalls(postmsg, signalevent)
to handle these hypercalls by QEMU.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org

Andrey Smetanin (5):
  kvm/x86: Rename Hyper-V long spin wait hypercall
  drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
  kvm/x86: Pass return code of kvm_emulate_hypercall
  kvm/x86: Hyper-V VMBus hypercall userspace exit
  kvm/x86: Reject Hyper-V hypercall continuation

 Documentation/virtual/kvm/api.txt  |  8 ++++++++
 arch/x86/include/uapi/asm/hyperv.h |  4 +++-
 arch/x86/kvm/hyperv.c              | 39 +++++++++++++++++++++++++++++---------
 arch/x86/kvm/hyperv.h              |  1 +
 arch/x86/kvm/svm.c                 |  3 +--
 arch/x86/kvm/vmx.c                 |  3 +--
 arch/x86/kvm/x86.c                 |  3 +++
 drivers/hv/hv.c                    |  5 +++--
 drivers/hv/hyperv_vmbus.h          |  6 ------
 include/uapi/linux/kvm.h           |  7 +++++++
 10 files changed, 57 insertions(+), 22 deletions(-)

-- 
2.4.3

[PATCH v1 1/5] kvm/x86: Rename Hyper-V long spin wait hypercall

[Andrey Smetanin]

Rename HV_X64_HV_NOTIFY_LONG_SPIN_WAIT
by HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT. So
the name better reflects hypercall codes accessory.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 arch/x86/include/uapi/asm/hyperv.h | 2 +-
 arch/x86/kvm/hyperv.c              | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 7956412..0c50fab 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -226,7 +226,7 @@
 		(~((1ull << HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT) - 1))
 
 /* Declare the various hypercall operations. */
-#define HV_X64_HV_NOTIFY_LONG_SPIN_WAIT		0x0008
+#define HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
 
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE		0x00000001
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT	12
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index c58ba67..f1a42e1 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1084,7 +1084,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 	trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
 
 	switch (code) {
-	case HV_X64_HV_NOTIFY_LONG_SPIN_WAIT:
+	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
 		kvm_vcpu_on_spin(vcpu);
 		break;
 	default:
-- 
2.4.3

[Qemu-devel] [PATCH v1 1/5] kvm/x86: Rename Hyper-V long spin wait hypercall

[Andrey Smetanin]

Rename HV_X64_HV_NOTIFY_LONG_SPIN_WAIT
by HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT. So
the name better reflects hypercall codes accessory.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 arch/x86/include/uapi/asm/hyperv.h | 2 +-
 arch/x86/kvm/hyperv.c              | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 7956412..0c50fab 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -226,7 +226,7 @@
 		(~((1ull << HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT) - 1))
 
 /* Declare the various hypercall operations. */
-#define HV_X64_HV_NOTIFY_LONG_SPIN_WAIT		0x0008
+#define HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
 
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE		0x00000001
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT	12
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index c58ba67..f1a42e1 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1084,7 +1084,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 	trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
 
 	switch (code) {
-	case HV_X64_HV_NOTIFY_LONG_SPIN_WAIT:
+	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
 		kvm_vcpu_on_spin(vcpu);
 		break;
 	default:
-- 
2.4.3

[PATCH v1 2/5] drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header

[Andrey Smetanin]

VMBus hypercall codes inside Hyper-V UAPI header will
be used by QEMU to implement VMBus host devices support.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org

---
 arch/x86/include/uapi/asm/hyperv.h | 2 ++
 drivers/hv/hv.c                    | 5 +++--
 drivers/hv/hyperv_vmbus.h          | 6 ------
 3 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 0c50fab..bc1c8a9 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -227,6 +227,8 @@
 
 /* Declare the various hypercall operations. */
 #define HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
+#define HV_X64_HCALL_POST_MESSAGE			0x005c
+#define HV_X64_HCALL_SIGNAL_EVENT			0x005d
 
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE		0x00000001
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT	12
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 6341be8..56437d5 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -329,7 +329,7 @@ int hv_post_message(union hv_connection_id connection_id,
 	aligned_msg->payload_size = payload_size;
 	memcpy((void *)aligned_msg->payload, payload, payload_size);
 
-	status = do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL)
+	status = do_hypercall(HV_X64_HCALL_POST_MESSAGE, aligned_msg, NULL)
 		& 0xFFFF;
 
 	put_cpu();
@@ -347,7 +347,8 @@ u16 hv_signal_event(void *con_id)
 {
 	u16 status;
 
-	status = (do_hypercall(HVCALL_SIGNAL_EVENT, con_id, NULL) & 0xFFFF);
+	status = (do_hypercall(HV_X64_HCALL_SIGNAL_EVENT, con_id, NULL)
+		  & 0xFFFF);
 
 	return status;
 }
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 678663e..36cad1f 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -251,12 +251,6 @@ struct hv_monitor_page {
 	u8 rsvdz4[1984];
 };
 
-/* Declare the various hypercall operations. */
-enum hv_call_code {
-	HVCALL_POST_MESSAGE	= 0x005c,
-	HVCALL_SIGNAL_EVENT	= 0x005d,
-};
-
 /* Definition of the hv_post_message hypercall input structure. */
 struct hv_input_post_message {
 	union hv_connection_id connectionid;
-- 
2.4.3

[Qemu-devel] [PATCH v1 2/5] drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header

[Andrey Smetanin]

VMBus hypercall codes inside Hyper-V UAPI header will
be used by QEMU to implement VMBus host devices support.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org

---
 arch/x86/include/uapi/asm/hyperv.h | 2 ++
 drivers/hv/hv.c                    | 5 +++--
 drivers/hv/hyperv_vmbus.h          | 6 ------
 3 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 0c50fab..bc1c8a9 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -227,6 +227,8 @@
 
 /* Declare the various hypercall operations. */
 #define HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
+#define HV_X64_HCALL_POST_MESSAGE			0x005c
+#define HV_X64_HCALL_SIGNAL_EVENT			0x005d
 
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE		0x00000001
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT	12
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 6341be8..56437d5 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -329,7 +329,7 @@ int hv_post_message(union hv_connection_id connection_id,
 	aligned_msg->payload_size = payload_size;
 	memcpy((void *)aligned_msg->payload, payload, payload_size);
 
-	status = do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL)
+	status = do_hypercall(HV_X64_HCALL_POST_MESSAGE, aligned_msg, NULL)
 		& 0xFFFF;
 
 	put_cpu();
@@ -347,7 +347,8 @@ u16 hv_signal_event(void *con_id)
 {
 	u16 status;
 
-	status = (do_hypercall(HVCALL_SIGNAL_EVENT, con_id, NULL) & 0xFFFF);
+	status = (do_hypercall(HV_X64_HCALL_SIGNAL_EVENT, con_id, NULL)
+		  & 0xFFFF);
 
 	return status;
 }
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 678663e..36cad1f 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -251,12 +251,6 @@ struct hv_monitor_page {
 	u8 rsvdz4[1984];
 };
 
-/* Declare the various hypercall operations. */
-enum hv_call_code {
-	HVCALL_POST_MESSAGE	= 0x005c,
-	HVCALL_SIGNAL_EVENT	= 0x005d,
-};
-
 /* Definition of the hv_post_message hypercall input structure. */
 struct hv_input_post_message {
 	union hv_connection_id connectionid;
-- 
2.4.3

[PATCH v1 3/5] kvm/x86: Pass return code of kvm_emulate_hypercall

[Andrey Smetanin]

Pass the return code from kvm_emulate_hypercall on to the caller,
in order to allow it to indicate to the userspace that
the hypercall has to be handled there.

Also adjust all the existing code paths to return 1 to make sure the
hypercall isn't passed to the userspace without setting kvm_run
appropriately.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 arch/x86/kvm/hyperv.c | 2 +-
 arch/x86/kvm/svm.c    | 3 +--
 arch/x86/kvm/vmx.c    | 3 +--
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index f1a42e1..0e7c90f 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1055,7 +1055,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 	 */
 	if (kvm_x86_ops->get_cpl(vcpu) != 0 || !is_protmode(vcpu)) {
 		kvm_queue_exception(vcpu, UD_VECTOR);
-		return 0;
+		return 1;
 	}
 
 	longmode = is_64_bit_mode(vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index af34215..5fd8a5b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1858,8 +1858,7 @@ static int halt_interception(struct vcpu_svm *svm)
 static int vmmcall_interception(struct vcpu_svm *svm)
 {
 	svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
-	kvm_emulate_hypercall(&svm->vcpu);
-	return 1;
+	return kvm_emulate_hypercall(&svm->vcpu);
 }
 
 static unsigned long nested_svm_get_tdp_cr3(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 62d958a..762c18e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5747,8 +5747,7 @@ static int handle_halt(struct kvm_vcpu *vcpu)
 
 static int handle_vmcall(struct kvm_vcpu *vcpu)
 {
-	kvm_emulate_hypercall(vcpu);
-	return 1;
+	return kvm_emulate_hypercall(vcpu);
 }
 
 static int handle_invd(struct kvm_vcpu *vcpu)
-- 
2.4.3

[Qemu-devel] [PATCH v1 3/5] kvm/x86: Pass return code of kvm_emulate_hypercall

[Andrey Smetanin]

Pass the return code from kvm_emulate_hypercall on to the caller,
in order to allow it to indicate to the userspace that
the hypercall has to be handled there.

Also adjust all the existing code paths to return 1 to make sure the
hypercall isn't passed to the userspace without setting kvm_run
appropriately.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 arch/x86/kvm/hyperv.c | 2 +-
 arch/x86/kvm/svm.c    | 3 +--
 arch/x86/kvm/vmx.c    | 3 +--
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index f1a42e1..0e7c90f 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1055,7 +1055,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 	 */
 	if (kvm_x86_ops->get_cpl(vcpu) != 0 || !is_protmode(vcpu)) {
 		kvm_queue_exception(vcpu, UD_VECTOR);
-		return 0;
+		return 1;
 	}
 
 	longmode = is_64_bit_mode(vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index af34215..5fd8a5b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1858,8 +1858,7 @@ static int halt_interception(struct vcpu_svm *svm)
 static int vmmcall_interception(struct vcpu_svm *svm)
 {
 	svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
-	kvm_emulate_hypercall(&svm->vcpu);
-	return 1;
+	return kvm_emulate_hypercall(&svm->vcpu);
 }
 
 static unsigned long nested_svm_get_tdp_cr3(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 62d958a..762c18e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5747,8 +5747,7 @@ static int handle_halt(struct kvm_vcpu *vcpu)
 
 static int handle_vmcall(struct kvm_vcpu *vcpu)
 {
-	kvm_emulate_hypercall(vcpu);
-	return 1;
+	return kvm_emulate_hypercall(vcpu);
 }
 
 static int handle_invd(struct kvm_vcpu *vcpu)
-- 
2.4.3

[PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Andrey Smetanin]

The patch implements KVM_EXIT_HV_HCALL functionality
for Hyper-V VMBus hypercalls: HV_X64_HCALL_POST_MESSAGE,
HV_X64_HCALL_SIGNAL_EVENT.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 Documentation/virtual/kvm/api.txt |  8 ++++++++
 arch/x86/kvm/hyperv.c             | 28 +++++++++++++++++++++-------
 arch/x86/kvm/hyperv.h             |  1 +
 arch/x86/kvm/x86.c                |  3 +++
 include/uapi/linux/kvm.h          |  7 +++++++
 5 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 053f613..23d4b9d 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
 event/message pages and to enable/disable SynIC messages/events processing
 in userspace.
 
+		/* KVM_EXIT_HYPERV_HCALL */
+		struct {
+			__u64 input;
+			__u64 params[2];
+			__u64 result;
+		} hv_hcall;
+Indicates that the VCPU exits into userspace to process some guest
+Hyper-V hypercalls.
 		/* Fix the size of the union. */
 		char padding[256];
 	};
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 0e7c90f..76c9ec4 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1087,18 +1087,32 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
 		kvm_vcpu_on_spin(vcpu);
 		break;
+	case HV_X64_HCALL_POST_MESSAGE:
+	case HV_X64_HCALL_SIGNAL_EVENT:
+		vcpu->run->exit_reason = KVM_EXIT_HYPERV_HCALL;
+		vcpu->run->hv_hcall.input = param;
+		vcpu->run->hv_hcall.params[0] = ingpa;
+		vcpu->run->hv_hcall.params[1] = outgpa;
+		return 0;
 	default:
 		res = HV_STATUS_INVALID_HYPERCALL_CODE;
 		break;
 	}
 
 	ret = res | (((u64)rep_done & 0xfff) << 32);
-	if (longmode) {
-		kvm_register_write(vcpu, VCPU_REGS_RAX, ret);
-	} else {
-		kvm_register_write(vcpu, VCPU_REGS_RDX, ret >> 32);
-		kvm_register_write(vcpu, VCPU_REGS_RAX, ret & 0xffffffff);
-	}
-
+	kvm_hv_hypercall_set_result(vcpu, ret);
 	return 1;
 }
+
+void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
+{
+	bool longmode;
+
+	longmode = is_64_bit_mode(vcpu);
+	if (longmode)
+		kvm_register_write(vcpu, VCPU_REGS_RAX, result);
+	else {
+		kvm_register_write(vcpu, VCPU_REGS_RDX, result >> 32);
+		kvm_register_write(vcpu, VCPU_REGS_RAX, result & 0xffffffff);
+	}
+}
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 60eccd4..64a4a3b 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -52,6 +52,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
 
 bool kvm_hv_hypercall_enabled(struct kvm *kvm);
 int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
+void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result);
 
 void kvm_hv_irq_routing_update(struct kvm *kvm);
 int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fad1d09..6ad3599 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6886,6 +6886,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	} else
 		WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
 
+	if (unlikely(kvm_run->exit_reason == KVM_EXIT_HYPERV_HCALL))
+		kvm_hv_hypercall_set_result(vcpu, kvm_run->hv_hcall.result);
+
 	r = vcpu_run(vcpu);
 
 out:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 9da9051..a62c4fb 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -199,6 +199,7 @@ struct kvm_hyperv_exit {
 #define KVM_EXIT_S390_STSI        25
 #define KVM_EXIT_IOAPIC_EOI       26
 #define KVM_EXIT_HYPERV           27
+#define KVM_EXIT_HYPERV_HCALL     28
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
@@ -355,6 +356,12 @@ struct kvm_run {
 		} eoi;
 		/* KVM_EXIT_HYPERV */
 		struct kvm_hyperv_exit hyperv;
+		/* KVM_EXIT_HYPERV_HCALL */
+		struct {
+			__u64 input;
+			__u64 params[2];
+			__u64 result;
+		} hv_hcall;
 		/* Fix the size of the union. */
 		char padding[256];
 	};
-- 
2.4.3

[Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Andrey Smetanin]

The patch implements KVM_EXIT_HV_HCALL functionality
for Hyper-V VMBus hypercalls: HV_X64_HCALL_POST_MESSAGE,
HV_X64_HCALL_SIGNAL_EVENT.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 Documentation/virtual/kvm/api.txt |  8 ++++++++
 arch/x86/kvm/hyperv.c             | 28 +++++++++++++++++++++-------
 arch/x86/kvm/hyperv.h             |  1 +
 arch/x86/kvm/x86.c                |  3 +++
 include/uapi/linux/kvm.h          |  7 +++++++
 5 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 053f613..23d4b9d 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
 event/message pages and to enable/disable SynIC messages/events processing
 in userspace.
 
+		/* KVM_EXIT_HYPERV_HCALL */
+		struct {
+			__u64 input;
+			__u64 params[2];
+			__u64 result;
+		} hv_hcall;
+Indicates that the VCPU exits into userspace to process some guest
+Hyper-V hypercalls.
 		/* Fix the size of the union. */
 		char padding[256];
 	};
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 0e7c90f..76c9ec4 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1087,18 +1087,32 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
 		kvm_vcpu_on_spin(vcpu);
 		break;
+	case HV_X64_HCALL_POST_MESSAGE:
+	case HV_X64_HCALL_SIGNAL_EVENT:
+		vcpu->run->exit_reason = KVM_EXIT_HYPERV_HCALL;
+		vcpu->run->hv_hcall.input = param;
+		vcpu->run->hv_hcall.params[0] = ingpa;
+		vcpu->run->hv_hcall.params[1] = outgpa;
+		return 0;
 	default:
 		res = HV_STATUS_INVALID_HYPERCALL_CODE;
 		break;
 	}
 
 	ret = res | (((u64)rep_done & 0xfff) << 32);
-	if (longmode) {
-		kvm_register_write(vcpu, VCPU_REGS_RAX, ret);
-	} else {
-		kvm_register_write(vcpu, VCPU_REGS_RDX, ret >> 32);
-		kvm_register_write(vcpu, VCPU_REGS_RAX, ret & 0xffffffff);
-	}
-
+	kvm_hv_hypercall_set_result(vcpu, ret);
 	return 1;
 }
+
+void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
+{
+	bool longmode;
+
+	longmode = is_64_bit_mode(vcpu);
+	if (longmode)
+		kvm_register_write(vcpu, VCPU_REGS_RAX, result);
+	else {
+		kvm_register_write(vcpu, VCPU_REGS_RDX, result >> 32);
+		kvm_register_write(vcpu, VCPU_REGS_RAX, result & 0xffffffff);
+	}
+}
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 60eccd4..64a4a3b 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -52,6 +52,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
 
 bool kvm_hv_hypercall_enabled(struct kvm *kvm);
 int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
+void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result);
 
 void kvm_hv_irq_routing_update(struct kvm *kvm);
 int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fad1d09..6ad3599 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6886,6 +6886,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	} else
 		WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
 
+	if (unlikely(kvm_run->exit_reason == KVM_EXIT_HYPERV_HCALL))
+		kvm_hv_hypercall_set_result(vcpu, kvm_run->hv_hcall.result);
+
 	r = vcpu_run(vcpu);
 
 out:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 9da9051..a62c4fb 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -199,6 +199,7 @@ struct kvm_hyperv_exit {
 #define KVM_EXIT_S390_STSI        25
 #define KVM_EXIT_IOAPIC_EOI       26
 #define KVM_EXIT_HYPERV           27
+#define KVM_EXIT_HYPERV_HCALL     28
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
@@ -355,6 +356,12 @@ struct kvm_run {
 		} eoi;
 		/* KVM_EXIT_HYPERV */
 		struct kvm_hyperv_exit hyperv;
+		/* KVM_EXIT_HYPERV_HCALL */
+		struct {
+			__u64 input;
+			__u64 params[2];
+			__u64 result;
+		} hv_hcall;
 		/* Fix the size of the union. */
 		char padding[256];
 	};
-- 
2.4.3

[PATCH v1 5/5] kvm/x86: Reject Hyper-V hypercall continuation

[Andrey Smetanin]

Currently we do not support Hyper-V hypercall continuation
so reject it.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 arch/x86/kvm/hyperv.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 76c9ec4..bc4884e 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1083,6 +1083,12 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
 
+	/* Hypercall continuation is not supported yet */
+	if (rep_cnt || rep_idx) {
+		res = HV_STATUS_INVALID_HYPERCALL_CODE;
+		goto set_result;
+	}
+
 	switch (code) {
 	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
 		kvm_vcpu_on_spin(vcpu);
@@ -1099,6 +1105,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		break;
 	}
 
+set_result:
 	ret = res | (((u64)rep_done & 0xfff) << 32);
 	kvm_hv_hypercall_set_result(vcpu, ret);
 	return 1;
-- 
2.4.3

[Qemu-devel] [PATCH v1 5/5] kvm/x86: Reject Hyper-V hypercall continuation

[Andrey Smetanin]

Currently we do not support Hyper-V hypercall continuation
so reject it.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
---
 arch/x86/kvm/hyperv.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 76c9ec4..bc4884e 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1083,6 +1083,12 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
 
+	/* Hypercall continuation is not supported yet */
+	if (rep_cnt || rep_idx) {
+		res = HV_STATUS_INVALID_HYPERCALL_CODE;
+		goto set_result;
+	}
+
 	switch (code) {
 	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
 		kvm_vcpu_on_spin(vcpu);
@@ -1099,6 +1105,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		break;
 	}
 
+set_result:
 	ret = res | (((u64)rep_done & 0xfff) << 32);
 	kvm_hv_hypercall_set_result(vcpu, ret);
 	return 1;
-- 
2.4.3

Re: [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Andrey Smetanin]

Paolo,

Could you please force these patches applied
during current merge window. We need them
very, because they are last patches for KVM which
are required to start development of Hyper-V
VMBus devices in QEMU side.

P.S.:
We have created our public repo (based on current kvm/queue) to fetch
our latest changes in KVM code to support Hyper-V VMBus:

https://src.openvz.org/projects/UP/repos/kvm_hyperv/commits?until=refs%2Fheads%2Fvmbus_hypercall

Thanks,
Andrey

On 01/12/2016 01:50 PM, Andrey Smetanin wrote:

> The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
> for Hyper-V VMBus hypercalls(postmsg, signalevent)
> to handle these hypercalls by QEMU.
>
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org
>
> Andrey Smetanin (5):
>    kvm/x86: Rename Hyper-V long spin wait hypercall
>    drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
>    kvm/x86: Pass return code of kvm_emulate_hypercall
>    kvm/x86: Hyper-V VMBus hypercall userspace exit
>    kvm/x86: Reject Hyper-V hypercall continuation
>
>   Documentation/virtual/kvm/api.txt  |  8 ++++++++
>   arch/x86/include/uapi/asm/hyperv.h |  4 +++-
>   arch/x86/kvm/hyperv.c              | 39 +++++++++++++++++++++++++++++---------
>   arch/x86/kvm/hyperv.h              |  1 +
>   arch/x86/kvm/svm.c                 |  3 +--
>   arch/x86/kvm/vmx.c                 |  3 +--
>   arch/x86/kvm/x86.c                 |  3 +++
>   drivers/hv/hv.c                    |  5 +++--
>   drivers/hv/hyperv_vmbus.h          |  6 ------
>   include/uapi/linux/kvm.h           |  7 +++++++
>   10 files changed, 57 insertions(+), 22 deletions(-)
>

Re: [Qemu-devel] [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Andrey Smetanin]

Paolo,

Could you please force these patches applied
during current merge window. We need them
very, because they are last patches for KVM which
are required to start development of Hyper-V
VMBus devices in QEMU side.

P.S.:
We have created our public repo (based on current kvm/queue) to fetch
our latest changes in KVM code to support Hyper-V VMBus:

https://src.openvz.org/projects/UP/repos/kvm_hyperv/commits?until=refs%2Fheads%2Fvmbus_hypercall

Thanks,
Andrey

On 01/12/2016 01:50 PM, Andrey Smetanin wrote:

> The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
> for Hyper-V VMBus hypercalls(postmsg, signalevent)
> to handle these hypercalls by QEMU.
>
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org
>
> Andrey Smetanin (5):
>    kvm/x86: Rename Hyper-V long spin wait hypercall
>    drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
>    kvm/x86: Pass return code of kvm_emulate_hypercall
>    kvm/x86: Hyper-V VMBus hypercall userspace exit
>    kvm/x86: Reject Hyper-V hypercall continuation
>
>   Documentation/virtual/kvm/api.txt  |  8 ++++++++
>   arch/x86/include/uapi/asm/hyperv.h |  4 +++-
>   arch/x86/kvm/hyperv.c              | 39 +++++++++++++++++++++++++++++---------
>   arch/x86/kvm/hyperv.h              |  1 +
>   arch/x86/kvm/svm.c                 |  3 +--
>   arch/x86/kvm/vmx.c                 |  3 +--
>   arch/x86/kvm/x86.c                 |  3 +++
>   drivers/hv/hv.c                    |  5 +++--
>   drivers/hv/hyperv_vmbus.h          |  6 ------
>   include/uapi/linux/kvm.h           |  7 +++++++
>   10 files changed, 57 insertions(+), 22 deletions(-)
>

RE: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Pavel Fedin]

 Hello!

> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
>  event/message pages and to enable/disable SynIC messages/events processing
>  in userspace.
> 
> +		/* KVM_EXIT_HYPERV_HCALL */
> +		struct {
> +			__u64 input;
> +			__u64 params[2];
> +			__u64 result;
> +		} hv_hcall;
> +Indicates that the VCPU exits into userspace to process some guest
> +Hyper-V hypercalls.

 Why introducing this? We already have KVM_EXIT_HYPERCALL, which is exactly the same. AFAIK it's not used at the moment.
 Additionally, in theory we could have hypercalls handled in userspace for something else except HyperV. And not only for x86.

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Pavel Fedin]

 Hello!

> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
>  event/message pages and to enable/disable SynIC messages/events processing
>  in userspace.
> 
> +		/* KVM_EXIT_HYPERV_HCALL */
> +		struct {
> +			__u64 input;
> +			__u64 params[2];
> +			__u64 result;
> +		} hv_hcall;
> +Indicates that the VCPU exits into userspace to process some guest
> +Hyper-V hypercalls.

 Why introducing this? We already have KVM_EXIT_HYPERCALL, which is exactly the same. AFAIK it's not used at the moment.
 Additionally, in theory we could have hypercalls handled in userspace for something else except HyperV. And not only for x86.

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Thu, Jan 14, 2016 at 11:30:43AM +0300, Pavel Fedin wrote:
> > --- a/Documentation/virtual/kvm/api.txt
> > +++ b/Documentation/virtual/kvm/api.txt
> > @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
> >  event/message pages and to enable/disable SynIC messages/events processing
> >  in userspace.
> > 
> > +		/* KVM_EXIT_HYPERV_HCALL */
> > +		struct {
> > +			__u64 input;
> > +			__u64 params[2];
> > +			__u64 result;
> > +		} hv_hcall;
> > +Indicates that the VCPU exits into userspace to process some guest
> > +Hyper-V hypercalls.
> 
>  Why introducing this? We already have KVM_EXIT_HYPERCALL, which is exactly the same. AFAIK it's not used at the moment.
>  Additionally, in theory we could have hypercalls handled in userspace for something else except HyperV. And not only for x86.

We thought reusing KVM_EXIT_HYPERCALL was a bad idea exactly because of
that.  Hypercalls are not universal, the calling and return conventions
are hypervisor-specific.  KVM already has to make the decision that the
particular vmexit is a HyperV hypercall; it appears unnatural to then
pass the data on to userspace in a generic structure and have them make
that decision again.

Roman.

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Thu, Jan 14, 2016 at 11:30:43AM +0300, Pavel Fedin wrote:
> > --- a/Documentation/virtual/kvm/api.txt
> > +++ b/Documentation/virtual/kvm/api.txt
> > @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
> >  event/message pages and to enable/disable SynIC messages/events processing
> >  in userspace.
> > 
> > +		/* KVM_EXIT_HYPERV_HCALL */
> > +		struct {
> > +			__u64 input;
> > +			__u64 params[2];
> > +			__u64 result;
> > +		} hv_hcall;
> > +Indicates that the VCPU exits into userspace to process some guest
> > +Hyper-V hypercalls.
> 
>  Why introducing this? We already have KVM_EXIT_HYPERCALL, which is exactly the same. AFAIK it's not used at the moment.
>  Additionally, in theory we could have hypercalls handled in userspace for something else except HyperV. And not only for x86.

We thought reusing KVM_EXIT_HYPERCALL was a bad idea exactly because of
that.  Hypercalls are not universal, the calling and return conventions
are hypervisor-specific.  KVM already has to make the decision that the
particular vmexit is a HyperV hypercall; it appears unnatural to then
pass the data on to userspace in a generic structure and have them make
that decision again.

Roman.

RE: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Pavel Fedin]

 Hello!

> We thought reusing KVM_EXIT_HYPERCALL was a bad idea exactly because of
> that.  Hypercalls are not universal, the calling and return conventions
> are hypervisor-specific.

 Treatment of them is hypervisor-specific, but from CPUs point of view they are the same. You load something into registers, and
execute hypercall instruction. So, you just need to pass registers in your structure. Or, you could even use generic register access
APIs.

>  KVM already has to make the decision that the
> particular vmexit is a HyperV hypercall; it appears unnatural to then
> pass the data on to userspace in a generic structure and have them make
> that decision again.

 Is it so difficult to make such a decision? The userland already knows what we are emulating.
 I'm afraid that in future we can end up in having 10 versions of KVM_EXIT_xxx_HYPERCALL with very small difference between them.
Will it be good?

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Pavel Fedin]

 Hello!

> We thought reusing KVM_EXIT_HYPERCALL was a bad idea exactly because of
> that.  Hypercalls are not universal, the calling and return conventions
> are hypervisor-specific.

 Treatment of them is hypervisor-specific, but from CPUs point of view they are the same. You load something into registers, and
execute hypercall instruction. So, you just need to pass registers in your structure. Or, you could even use generic register access
APIs.

>  KVM already has to make the decision that the
> particular vmexit is a HyperV hypercall; it appears unnatural to then
> pass the data on to userspace in a generic structure and have them make
> that decision again.

 Is it so difficult to make such a decision? The userland already knows what we are emulating.
 I'm afraid that in future we can end up in having 10 versions of KVM_EXIT_xxx_HYPERCALL with very small difference between them.
Will it be good?

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Thu, Jan 14, 2016 at 01:50:20PM +0300, Pavel Fedin wrote:
> > We thought reusing KVM_EXIT_HYPERCALL was a bad idea exactly because of
> > that.  Hypercalls are not universal, the calling and return conventions
> > are hypervisor-specific.
> 
>  Treatment of them is hypervisor-specific, but from CPUs point of view they are the same. You load something into registers, and
> execute hypercall instruction.

... and you get something in the registers on return (all that is from
guest POV).  Right.  The differences are, however, which registers are
used for parameters and return values, how they are encoded, etc.

> So, you just need to pass registers in your structure.

Which ones?  This is going to be hypervisor- and arch-specific.

> Or, you could even use generic register access APIs.

With an extra ioctl?  This is going to be expensive.

> >  KVM already has to make the decision that the
> > particular vmexit is a HyperV hypercall; it appears unnatural to then
> > pass the data on to userspace in a generic structure and have them make
> > that decision again.
> 
>  Is it so difficult to make such a decision? The userland already knows what we are emulating.

It isn't terribly difficult, but KVM has to do all that already, as it
handles some of the hypercalls in the kernel.  I don't think duplicating
this (and also designing a generic marshalling scheme) is profitable
compared to saving a vcpu exit code.

>  I'm afraid that in future we can end up in having 10 versions of KVM_EXIT_xxx_HYPERCALL with very small difference between them.
> Will it be good?

I don't see it to be a problem.

Roman.

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Thu, Jan 14, 2016 at 01:50:20PM +0300, Pavel Fedin wrote:
> > We thought reusing KVM_EXIT_HYPERCALL was a bad idea exactly because of
> > that.  Hypercalls are not universal, the calling and return conventions
> > are hypervisor-specific.
> 
>  Treatment of them is hypervisor-specific, but from CPUs point of view they are the same. You load something into registers, and
> execute hypercall instruction.

... and you get something in the registers on return (all that is from
guest POV).  Right.  The differences are, however, which registers are
used for parameters and return values, how they are encoded, etc.

> So, you just need to pass registers in your structure.

Which ones?  This is going to be hypervisor- and arch-specific.

> Or, you could even use generic register access APIs.

With an extra ioctl?  This is going to be expensive.

> >  KVM already has to make the decision that the
> > particular vmexit is a HyperV hypercall; it appears unnatural to then
> > pass the data on to userspace in a generic structure and have them make
> > that decision again.
> 
>  Is it so difficult to make such a decision? The userland already knows what we are emulating.

It isn't terribly difficult, but KVM has to do all that already, as it
handles some of the hypercalls in the kernel.  I don't think duplicating
this (and also designing a generic marshalling scheme) is profitable
compared to saving a vcpu exit code.

>  I'm afraid that in future we can end up in having 10 versions of KVM_EXIT_xxx_HYPERCALL with very small difference between them.
> Will it be good?

I don't see it to be a problem.

Roman.

Re: [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Denis V. Lunev]

On 01/12/2016 01:50 PM, Andrey Smetanin wrote:
> The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
> for Hyper-V VMBus hypercalls(postmsg, signalevent)
> to handle these hypercalls by QEMU.
>
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org
>
> Andrey Smetanin (5):
>    kvm/x86: Rename Hyper-V long spin wait hypercall
>    drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
>    kvm/x86: Pass return code of kvm_emulate_hypercall
>    kvm/x86: Hyper-V VMBus hypercall userspace exit
>    kvm/x86: Reject Hyper-V hypercall continuation
>
>   Documentation/virtual/kvm/api.txt  |  8 ++++++++
>   arch/x86/include/uapi/asm/hyperv.h |  4 +++-
>   arch/x86/kvm/hyperv.c              | 39 +++++++++++++++++++++++++++++---------
>   arch/x86/kvm/hyperv.h              |  1 +
>   arch/x86/kvm/svm.c                 |  3 +--
>   arch/x86/kvm/vmx.c                 |  3 +--
>   arch/x86/kvm/x86.c                 |  3 +++
>   drivers/hv/hv.c                    |  5 +++--
>   drivers/hv/hyperv_vmbus.h          |  6 ------
>   include/uapi/linux/kvm.h           |  7 +++++++
>   10 files changed, 57 insertions(+), 22 deletions(-)
>
ping

Re: [Qemu-devel] [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Denis V. Lunev]

On 01/12/2016 01:50 PM, Andrey Smetanin wrote:
> The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
> for Hyper-V VMBus hypercalls(postmsg, signalevent)
> to handle these hypercalls by QEMU.
>
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org
>
> Andrey Smetanin (5):
>    kvm/x86: Rename Hyper-V long spin wait hypercall
>    drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
>    kvm/x86: Pass return code of kvm_emulate_hypercall
>    kvm/x86: Hyper-V VMBus hypercall userspace exit
>    kvm/x86: Reject Hyper-V hypercall continuation
>
>   Documentation/virtual/kvm/api.txt  |  8 ++++++++
>   arch/x86/include/uapi/asm/hyperv.h |  4 +++-
>   arch/x86/kvm/hyperv.c              | 39 +++++++++++++++++++++++++++++---------
>   arch/x86/kvm/hyperv.h              |  1 +
>   arch/x86/kvm/svm.c                 |  3 +--
>   arch/x86/kvm/vmx.c                 |  3 +--
>   arch/x86/kvm/x86.c                 |  3 +++
>   drivers/hv/hv.c                    |  5 +++--
>   drivers/hv/hyperv_vmbus.h          |  6 ------
>   include/uapi/linux/kvm.h           |  7 +++++++
>   10 files changed, 57 insertions(+), 22 deletions(-)
>
ping

Re: [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Paolo Bonzini]

On 19/01/2016 08:49, Denis V. Lunev wrote:
> On 01/12/2016 01:50 PM, Andrey Smetanin wrote:
>> The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
>> for Hyper-V VMBus hypercalls(postmsg, signalevent)
>> to handle these hypercalls by QEMU.
>>
>> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
>> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
>> CC: Gleb Natapov <gleb@kernel.org>
>> CC: Paolo Bonzini <pbonzini@redhat.com>
>> CC: Joerg Roedel <joro@8bytes.org>
>> CC: "K. Y. Srinivasan" <kys@microsoft.com>
>> CC: Haiyang Zhang <haiyangz@microsoft.com>
>> CC: Roman Kagan <rkagan@virtuozzo.com>
>> CC: Denis V. Lunev <den@openvz.org>
>> CC: qemu-devel@nongnu.org
>>
>> Andrey Smetanin (5):
>>    kvm/x86: Rename Hyper-V long spin wait hypercall
>>    drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
>>    kvm/x86: Pass return code of kvm_emulate_hypercall
>>    kvm/x86: Hyper-V VMBus hypercall userspace exit
>>    kvm/x86: Reject Hyper-V hypercall continuation
>>
>>   Documentation/virtual/kvm/api.txt  |  8 ++++++++
>>   arch/x86/include/uapi/asm/hyperv.h |  4 +++-
>>   arch/x86/kvm/hyperv.c              | 39
>> +++++++++++++++++++++++++++++---------
>>   arch/x86/kvm/hyperv.h              |  1 +
>>   arch/x86/kvm/svm.c                 |  3 +--
>>   arch/x86/kvm/vmx.c                 |  3 +--
>>   arch/x86/kvm/x86.c                 |  3 +++
>>   drivers/hv/hv.c                    |  5 +++--
>>   drivers/hv/hyperv_vmbus.h          |  6 ------
>>   include/uapi/linux/kvm.h           |  7 +++++++
>>   10 files changed, 57 insertions(+), 22 deletions(-)
>>
> ping

I'll try to get to this and the others tomorrow.

Paolo

Re: [Qemu-devel] [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Paolo Bonzini]

On 19/01/2016 08:49, Denis V. Lunev wrote:
> On 01/12/2016 01:50 PM, Andrey Smetanin wrote:
>> The patch implements userspace exit 'KVM_EXIT_HYPERV_HCALL'
>> for Hyper-V VMBus hypercalls(postmsg, signalevent)
>> to handle these hypercalls by QEMU.
>>
>> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
>> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
>> CC: Gleb Natapov <gleb@kernel.org>
>> CC: Paolo Bonzini <pbonzini@redhat.com>
>> CC: Joerg Roedel <joro@8bytes.org>
>> CC: "K. Y. Srinivasan" <kys@microsoft.com>
>> CC: Haiyang Zhang <haiyangz@microsoft.com>
>> CC: Roman Kagan <rkagan@virtuozzo.com>
>> CC: Denis V. Lunev <den@openvz.org>
>> CC: qemu-devel@nongnu.org
>>
>> Andrey Smetanin (5):
>>    kvm/x86: Rename Hyper-V long spin wait hypercall
>>    drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header
>>    kvm/x86: Pass return code of kvm_emulate_hypercall
>>    kvm/x86: Hyper-V VMBus hypercall userspace exit
>>    kvm/x86: Reject Hyper-V hypercall continuation
>>
>>   Documentation/virtual/kvm/api.txt  |  8 ++++++++
>>   arch/x86/include/uapi/asm/hyperv.h |  4 +++-
>>   arch/x86/kvm/hyperv.c              | 39
>> +++++++++++++++++++++++++++++---------
>>   arch/x86/kvm/hyperv.h              |  1 +
>>   arch/x86/kvm/svm.c                 |  3 +--
>>   arch/x86/kvm/vmx.c                 |  3 +--
>>   arch/x86/kvm/x86.c                 |  3 +++
>>   drivers/hv/hv.c                    |  5 +++--
>>   drivers/hv/hyperv_vmbus.h          |  6 ------
>>   include/uapi/linux/kvm.h           |  7 +++++++
>>   10 files changed, 57 insertions(+), 22 deletions(-)
>>
> ping

I'll try to get to this and the others tomorrow.

Paolo

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 12/01/2016 11:50, Andrey Smetanin wrote:
> The patch implements KVM_EXIT_HV_HCALL functionality
> for Hyper-V VMBus hypercalls: HV_X64_HCALL_POST_MESSAGE,
> HV_X64_HCALL_SIGNAL_EVENT.
> 
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org
> ---
>  Documentation/virtual/kvm/api.txt |  8 ++++++++
>  arch/x86/kvm/hyperv.c             | 28 +++++++++++++++++++++-------
>  arch/x86/kvm/hyperv.h             |  1 +
>  arch/x86/kvm/x86.c                |  3 +++
>  include/uapi/linux/kvm.h          |  7 +++++++
>  5 files changed, 40 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 053f613..23d4b9d 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
>  event/message pages and to enable/disable SynIC messages/events processing
>  in userspace.
>  
> +		/* KVM_EXIT_HYPERV_HCALL */
> +		struct {
> +			__u64 input;
> +			__u64 params[2];
> +			__u64 result;
> +		} hv_hcall;
> +Indicates that the VCPU exits into userspace to process some guest
> +Hyper-V hypercalls.

Is this something other than KVM_EXIT_HYPERV because of the previous
discussion about MSRs?  Otherwise, it definitely should be a separate
type of the existing KVM_EXIT_HYPERV exit.

(In fact, I do not think anymore that I will add the MSR exit in 4.5.
It's kind of against the KVM design to do "CPU things" outside the
kernel.  My conjecture is that MSRs are either simple and thus not
security sensitive, or complicated and thus require state that resides
in the kernel).

>  		/* Fix the size of the union. */
>  		char padding[256];
>  	};
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 0e7c90f..76c9ec4 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1087,18 +1087,32 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>  	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
>  		kvm_vcpu_on_spin(vcpu);
>  		break;
> +	case HV_X64_HCALL_POST_MESSAGE:
> +	case HV_X64_HCALL_SIGNAL_EVENT:
> +		vcpu->run->exit_reason = KVM_EXIT_HYPERV_HCALL;
> +		vcpu->run->hv_hcall.input = param;
> +		vcpu->run->hv_hcall.params[0] = ingpa;
> +		vcpu->run->hv_hcall.params[1] = outgpa;
> +		return 0;
>  	default:
>  		res = HV_STATUS_INVALID_HYPERCALL_CODE;
>  		break;
>  	}
>  
>  	ret = res | (((u64)rep_done & 0xfff) << 32);
> -	if (longmode) {
> -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret);
> -	} else {
> -		kvm_register_write(vcpu, VCPU_REGS_RDX, ret >> 32);
> -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret & 0xffffffff);
> -	}
> -
> +	kvm_hv_hypercall_set_result(vcpu, ret);
>  	return 1;
>  }
> +
> +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
> +{
> +	bool longmode;
> +
> +	longmode = is_64_bit_mode(vcpu);
> +	if (longmode)
> +		kvm_register_write(vcpu, VCPU_REGS_RAX, result);
> +	else {
> +		kvm_register_write(vcpu, VCPU_REGS_RDX, result >> 32);
> +		kvm_register_write(vcpu, VCPU_REGS_RAX, result & 0xffffffff);
> +	}
> +}
> diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> index 60eccd4..64a4a3b 100644
> --- a/arch/x86/kvm/hyperv.h
> +++ b/arch/x86/kvm/hyperv.h
> @@ -52,6 +52,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
>  
>  bool kvm_hv_hypercall_enabled(struct kvm *kvm);
>  int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
> +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result);
>  
>  void kvm_hv_irq_routing_update(struct kvm *kvm);
>  int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fad1d09..6ad3599 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6886,6 +6886,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	} else
>  		WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
>  
> +	if (unlikely(kvm_run->exit_reason == KVM_EXIT_HYPERV_HCALL))
> +		kvm_hv_hypercall_set_result(vcpu, kvm_run->hv_hcall.result);
> +
>  	r = vcpu_run(vcpu);
>  
>  out:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 9da9051..a62c4fb 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -199,6 +199,7 @@ struct kvm_hyperv_exit {
>  #define KVM_EXIT_S390_STSI        25
>  #define KVM_EXIT_IOAPIC_EOI       26
>  #define KVM_EXIT_HYPERV           27
> +#define KVM_EXIT_HYPERV_HCALL     28
>  
>  /* For KVM_EXIT_INTERNAL_ERROR */
>  /* Emulate instruction failed. */
> @@ -355,6 +356,12 @@ struct kvm_run {
>  		} eoi;
>  		/* KVM_EXIT_HYPERV */
>  		struct kvm_hyperv_exit hyperv;
> +		/* KVM_EXIT_HYPERV_HCALL */
> +		struct {
> +			__u64 input;
> +			__u64 params[2];
> +			__u64 result;

Please put result before params, so that it's possible to add more
parameters in the future.

Paolo

> +		} hv_hcall;
>  		/* Fix the size of the union. */
>  		char padding[256];
>  	};
> 

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 12/01/2016 11:50, Andrey Smetanin wrote:
> The patch implements KVM_EXIT_HV_HCALL functionality
> for Hyper-V VMBus hypercalls: HV_X64_HCALL_POST_MESSAGE,
> HV_X64_HCALL_SIGNAL_EVENT.
> 
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org
> ---
>  Documentation/virtual/kvm/api.txt |  8 ++++++++
>  arch/x86/kvm/hyperv.c             | 28 +++++++++++++++++++++-------
>  arch/x86/kvm/hyperv.h             |  1 +
>  arch/x86/kvm/x86.c                |  3 +++
>  include/uapi/linux/kvm.h          |  7 +++++++
>  5 files changed, 40 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 053f613..23d4b9d 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
>  event/message pages and to enable/disable SynIC messages/events processing
>  in userspace.
>  
> +		/* KVM_EXIT_HYPERV_HCALL */
> +		struct {
> +			__u64 input;
> +			__u64 params[2];
> +			__u64 result;
> +		} hv_hcall;
> +Indicates that the VCPU exits into userspace to process some guest
> +Hyper-V hypercalls.

Is this something other than KVM_EXIT_HYPERV because of the previous
discussion about MSRs?  Otherwise, it definitely should be a separate
type of the existing KVM_EXIT_HYPERV exit.

(In fact, I do not think anymore that I will add the MSR exit in 4.5.
It's kind of against the KVM design to do "CPU things" outside the
kernel.  My conjecture is that MSRs are either simple and thus not
security sensitive, or complicated and thus require state that resides
in the kernel).

>  		/* Fix the size of the union. */
>  		char padding[256];
>  	};
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 0e7c90f..76c9ec4 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1087,18 +1087,32 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>  	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
>  		kvm_vcpu_on_spin(vcpu);
>  		break;
> +	case HV_X64_HCALL_POST_MESSAGE:
> +	case HV_X64_HCALL_SIGNAL_EVENT:
> +		vcpu->run->exit_reason = KVM_EXIT_HYPERV_HCALL;
> +		vcpu->run->hv_hcall.input = param;
> +		vcpu->run->hv_hcall.params[0] = ingpa;
> +		vcpu->run->hv_hcall.params[1] = outgpa;
> +		return 0;
>  	default:
>  		res = HV_STATUS_INVALID_HYPERCALL_CODE;
>  		break;
>  	}
>  
>  	ret = res | (((u64)rep_done & 0xfff) << 32);
> -	if (longmode) {
> -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret);
> -	} else {
> -		kvm_register_write(vcpu, VCPU_REGS_RDX, ret >> 32);
> -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret & 0xffffffff);
> -	}
> -
> +	kvm_hv_hypercall_set_result(vcpu, ret);
>  	return 1;
>  }
> +
> +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
> +{
> +	bool longmode;
> +
> +	longmode = is_64_bit_mode(vcpu);
> +	if (longmode)
> +		kvm_register_write(vcpu, VCPU_REGS_RAX, result);
> +	else {
> +		kvm_register_write(vcpu, VCPU_REGS_RDX, result >> 32);
> +		kvm_register_write(vcpu, VCPU_REGS_RAX, result & 0xffffffff);
> +	}
> +}
> diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> index 60eccd4..64a4a3b 100644
> --- a/arch/x86/kvm/hyperv.h
> +++ b/arch/x86/kvm/hyperv.h
> @@ -52,6 +52,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
>  
>  bool kvm_hv_hypercall_enabled(struct kvm *kvm);
>  int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
> +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result);
>  
>  void kvm_hv_irq_routing_update(struct kvm *kvm);
>  int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fad1d09..6ad3599 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6886,6 +6886,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	} else
>  		WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
>  
> +	if (unlikely(kvm_run->exit_reason == KVM_EXIT_HYPERV_HCALL))
> +		kvm_hv_hypercall_set_result(vcpu, kvm_run->hv_hcall.result);
> +
>  	r = vcpu_run(vcpu);
>  
>  out:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 9da9051..a62c4fb 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -199,6 +199,7 @@ struct kvm_hyperv_exit {
>  #define KVM_EXIT_S390_STSI        25
>  #define KVM_EXIT_IOAPIC_EOI       26
>  #define KVM_EXIT_HYPERV           27
> +#define KVM_EXIT_HYPERV_HCALL     28
>  
>  /* For KVM_EXIT_INTERNAL_ERROR */
>  /* Emulate instruction failed. */
> @@ -355,6 +356,12 @@ struct kvm_run {
>  		} eoi;
>  		/* KVM_EXIT_HYPERV */
>  		struct kvm_hyperv_exit hyperv;
> +		/* KVM_EXIT_HYPERV_HCALL */
> +		struct {
> +			__u64 input;
> +			__u64 params[2];
> +			__u64 result;

Please put result before params, so that it's possible to add more
parameters in the future.

Paolo

> +		} hv_hcall;
>  		/* Fix the size of the union. */
>  		char padding[256];
>  	};
> 

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 14/01/2016 09:30, Pavel Fedin wrote:
>  Hello!
> 
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
>>  event/message pages and to enable/disable SynIC messages/events processing
>>  in userspace.
>>
>> +		/* KVM_EXIT_HYPERV_HCALL */
>> +		struct {
>> +			__u64 input;
>> +			__u64 params[2];
>> +			__u64 result;
>> +		} hv_hcall;
>> +Indicates that the VCPU exits into userspace to process some guest
>> +Hyper-V hypercalls.
> 
> Why introducing this? We already have KVM_EXIT_HYPERCALL, which is
> exactly the same. AFAIK it's not used at the moment.
> Additionally, in theory we could have hypercalls handled in
> userspace for something else except HyperV. And not only for x86.

Because, as the docs say, we don't want to do that.  We want to use
KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
can't do that for compatibility purposes.  This is the latter.  So we
should not add a new exit (I suggested elsewhere the existing hyper-v
exit) but we shouldn't use KVM_EXIT_HYPERCALL either.

There is a precedent in fact of using "something else than
KVM_EXIT_HYPERCALL" for interoperability/compatibility hypercalls,
namely KVM_EXIT_PAPR_HCALL.

Paolo

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 14/01/2016 09:30, Pavel Fedin wrote:
>  Hello!
> 
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
>>  event/message pages and to enable/disable SynIC messages/events processing
>>  in userspace.
>>
>> +		/* KVM_EXIT_HYPERV_HCALL */
>> +		struct {
>> +			__u64 input;
>> +			__u64 params[2];
>> +			__u64 result;
>> +		} hv_hcall;
>> +Indicates that the VCPU exits into userspace to process some guest
>> +Hyper-V hypercalls.
> 
> Why introducing this? We already have KVM_EXIT_HYPERCALL, which is
> exactly the same. AFAIK it's not used at the moment.
> Additionally, in theory we could have hypercalls handled in
> userspace for something else except HyperV. And not only for x86.

Because, as the docs say, we don't want to do that.  We want to use
KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
can't do that for compatibility purposes.  This is the latter.  So we
should not add a new exit (I suggested elsewhere the existing hyper-v
exit) but we shouldn't use KVM_EXIT_HYPERCALL either.

There is a precedent in fact of using "something else than
KVM_EXIT_HYPERCALL" for interoperability/compatibility hypercalls,
namely KVM_EXIT_PAPR_HCALL.

Paolo

Re: [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Paolo Bonzini]

On 19/01/2016 17:47, Paolo Bonzini wrote:
>> > ping
> I'll try to get to this and the others tomorrow.

There are a few changes to make, and I'd like KY to ack the first
patches, so I'll have to defer this to the next release.

Paolo

Re: [Qemu-devel] [PATCH v1 0/5] KVM: Hyper-V VMBus hypercalls

[Paolo Bonzini]

On 19/01/2016 17:47, Paolo Bonzini wrote:
>> > ping
> I'll try to get to this and the others tomorrow.

There are a few changes to make, and I'd like KY to ack the first
patches, so I'll have to defer this to the next release.

Paolo

RE: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Pavel Fedin]

 Hello!

> Because, as the docs say, we don't want to do that.

 Where do they say this? I remember that "we want to use KVM_EXIT_IO or KVM_EXIT_MMIO for handling device I/O". In other words - we
should not introduce anything that requires any other mechanism (e. g. hypercalls) to handle this. And that's all. By the way,
Hyper-V implementation contradicts this rule by itself. And i wonder why we need it at all, but, well, why not. So, Hyper-V violates
this rule only because it was designed by other people under different rules. And we have to follow these rules. So we have to
support hypercalls. And hypercalls cannot map to EXIT_IO or EXIT_MMIO, so...

>  We want to use
> KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
> can't do that for compatibility purposes.  This is the latter.

 Yes, basically this is what i told above...

>  So we
> should not add a new exit (I suggested elsewhere the existing hyper-v
> exit)

 Yes, this would also be more consistent i think, if we think subsystem-centric ("we are implementing Hyper-V") instead of
implementation-centric ("we are implementing hypercalls").

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Pavel Fedin]

 Hello!

> Because, as the docs say, we don't want to do that.

 Where do they say this? I remember that "we want to use KVM_EXIT_IO or KVM_EXIT_MMIO for handling device I/O". In other words - we
should not introduce anything that requires any other mechanism (e. g. hypercalls) to handle this. And that's all. By the way,
Hyper-V implementation contradicts this rule by itself. And i wonder why we need it at all, but, well, why not. So, Hyper-V violates
this rule only because it was designed by other people under different rules. And we have to follow these rules. So we have to
support hypercalls. And hypercalls cannot map to EXIT_IO or EXIT_MMIO, so...

>  We want to use
> KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
> can't do that for compatibility purposes.  This is the latter.

 Yes, basically this is what i told above...

>  So we
> should not add a new exit (I suggested elsewhere the existing hyper-v
> exit)

 Yes, this would also be more consistent i think, if we think subsystem-centric ("we are implementing Hyper-V") instead of
implementation-centric ("we are implementing hypercalls").

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia

Re: [PATCH v1 2/5] drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header

[KY Srinivasan]

> -----Original Message-----
> From: Andrey Smetanin [mailto:asmetanin@virtuozzo.com]
> Sent: Tuesday, January 12, 2016 2:51 AM
> To: kvm@vger.kernel.org
> Cc: Gleb Natapov <gleb@kernel.org>; Paolo Bonzini
> <pbonzini@redhat.com>; Joerg Roedel <joro@8bytes.org>; KY Srinivasan
> <kys@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>; Roman
> Kagan <rkagan@virtuozzo.com>; Denis V. Lunev <den@openvz.org>; qemu-
> devel@nongnu.org
> Subject: [PATCH v1 2/5] drivers/hv: Move VMBus hypercall codes into Hyper-
> V UAPI header
> 
> VMBus hypercall codes inside Hyper-V UAPI header will
> be used by QEMU to implement VMBus host devices support.
> 
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org

Acked-by: K. Y. Srinivasan <kys@microsoft.com>

> 
> ---
>  arch/x86/include/uapi/asm/hyperv.h | 2 ++
>  drivers/hv/hv.c                    | 5 +++--
>  drivers/hv/hyperv_vmbus.h          | 6 ------
>  3 files changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/include/uapi/asm/hyperv.h
> b/arch/x86/include/uapi/asm/hyperv.h
> index 0c50fab..bc1c8a9 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -227,6 +227,8 @@
> 
>  /* Declare the various hypercall operations. */
>  #define HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
> +#define HV_X64_HCALL_POST_MESSAGE			0x005c
> +#define HV_X64_HCALL_SIGNAL_EVENT			0x005d
> 
>  #define HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE		0x00000001
>  #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT	12
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 6341be8..56437d5 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -329,7 +329,7 @@ int hv_post_message(union hv_connection_id
> connection_id,
>  	aligned_msg->payload_size = payload_size;
>  	memcpy((void *)aligned_msg->payload, payload, payload_size);
> 
> -	status = do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL)
> +	status = do_hypercall(HV_X64_HCALL_POST_MESSAGE,
> aligned_msg, NULL)
>  		& 0xFFFF;
> 
>  	put_cpu();
> @@ -347,7 +347,8 @@ u16 hv_signal_event(void *con_id)
>  {
>  	u16 status;
> 
> -	status = (do_hypercall(HVCALL_SIGNAL_EVENT, con_id, NULL) &
> 0xFFFF);
> +	status = (do_hypercall(HV_X64_HCALL_SIGNAL_EVENT, con_id,
> NULL)
> +		  & 0xFFFF);
> 
>  	return status;
>  }
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 678663e..36cad1f 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -251,12 +251,6 @@ struct hv_monitor_page {
>  	u8 rsvdz4[1984];
>  };
> 
> -/* Declare the various hypercall operations. */
> -enum hv_call_code {
> -	HVCALL_POST_MESSAGE	= 0x005c,
> -	HVCALL_SIGNAL_EVENT	= 0x005d,
> -};
> -
>  /* Definition of the hv_post_message hypercall input structure. */
>  struct hv_input_post_message {
>  	union hv_connection_id connectionid;
> --
> 2.4.3

Re: [Qemu-devel] [PATCH v1 2/5] drivers/hv: Move VMBus hypercall codes into Hyper-V UAPI header

[KY Srinivasan]

> -----Original Message-----
> From: Andrey Smetanin [mailto:asmetanin@virtuozzo.com]
> Sent: Tuesday, January 12, 2016 2:51 AM
> To: kvm@vger.kernel.org
> Cc: Gleb Natapov <gleb@kernel.org>; Paolo Bonzini
> <pbonzini@redhat.com>; Joerg Roedel <joro@8bytes.org>; KY Srinivasan
> <kys@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>; Roman
> Kagan <rkagan@virtuozzo.com>; Denis V. Lunev <den@openvz.org>; qemu-
> devel@nongnu.org
> Subject: [PATCH v1 2/5] drivers/hv: Move VMBus hypercall codes into Hyper-
> V UAPI header
> 
> VMBus hypercall codes inside Hyper-V UAPI header will
> be used by QEMU to implement VMBus host devices support.
> 
> Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Joerg Roedel <joro@8bytes.org>
> CC: "K. Y. Srinivasan" <kys@microsoft.com>
> CC: Haiyang Zhang <haiyangz@microsoft.com>
> CC: Roman Kagan <rkagan@virtuozzo.com>
> CC: Denis V. Lunev <den@openvz.org>
> CC: qemu-devel@nongnu.org

Acked-by: K. Y. Srinivasan <kys@microsoft.com>

> 
> ---
>  arch/x86/include/uapi/asm/hyperv.h | 2 ++
>  drivers/hv/hv.c                    | 5 +++--
>  drivers/hv/hyperv_vmbus.h          | 6 ------
>  3 files changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/include/uapi/asm/hyperv.h
> b/arch/x86/include/uapi/asm/hyperv.h
> index 0c50fab..bc1c8a9 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -227,6 +227,8 @@
> 
>  /* Declare the various hypercall operations. */
>  #define HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
> +#define HV_X64_HCALL_POST_MESSAGE			0x005c
> +#define HV_X64_HCALL_SIGNAL_EVENT			0x005d
> 
>  #define HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE		0x00000001
>  #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT	12
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 6341be8..56437d5 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -329,7 +329,7 @@ int hv_post_message(union hv_connection_id
> connection_id,
>  	aligned_msg->payload_size = payload_size;
>  	memcpy((void *)aligned_msg->payload, payload, payload_size);
> 
> -	status = do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL)
> +	status = do_hypercall(HV_X64_HCALL_POST_MESSAGE,
> aligned_msg, NULL)
>  		& 0xFFFF;
> 
>  	put_cpu();
> @@ -347,7 +347,8 @@ u16 hv_signal_event(void *con_id)
>  {
>  	u16 status;
> 
> -	status = (do_hypercall(HVCALL_SIGNAL_EVENT, con_id, NULL) &
> 0xFFFF);
> +	status = (do_hypercall(HV_X64_HCALL_SIGNAL_EVENT, con_id,
> NULL)
> +		  & 0xFFFF);
> 
>  	return status;
>  }
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 678663e..36cad1f 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -251,12 +251,6 @@ struct hv_monitor_page {
>  	u8 rsvdz4[1984];
>  };
> 
> -/* Declare the various hypercall operations. */
> -enum hv_call_code {
> -	HVCALL_POST_MESSAGE	= 0x005c,
> -	HVCALL_SIGNAL_EVENT	= 0x005d,
> -};
> -
>  /* Definition of the hv_post_message hypercall input structure. */
>  struct hv_input_post_message {
>  	union hv_connection_id connectionid;
> --
> 2.4.3

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Wed, Jan 20, 2016 at 02:59:08PM +0100, Paolo Bonzini wrote:
> >> --- a/Documentation/virtual/kvm/api.txt
> >> +++ b/Documentation/virtual/kvm/api.txt
> >> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
> >>  event/message pages and to enable/disable SynIC messages/events processing
> >>  in userspace.
> >>
> >> +		/* KVM_EXIT_HYPERV_HCALL */
> >> +		struct {
> >> +			__u64 input;
> >> +			__u64 params[2];
> >> +			__u64 result;
> >> +		} hv_hcall;
> >> +Indicates that the VCPU exits into userspace to process some guest
> >> +Hyper-V hypercalls.
> > 
> > Why introducing this? We already have KVM_EXIT_HYPERCALL, which is
> > exactly the same. AFAIK it's not used at the moment.
> > Additionally, in theory we could have hypercalls handled in
> > userspace for something else except HyperV. And not only for x86.
> 
> Because, as the docs say, we don't want to do that.  We want to use
> KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
> can't do that for compatibility purposes.

I must admit I saw this part in the docs but failed to understand it.

Is it supposed to mean that we want to avoid using hypercalls as a means
of guest communications with the host userspace in general, and use PIO
or MMIO instead, unless hypercalls are mandated by a guest implemenation
we can't affect (as is the case for Hyper-V)?

Because *implementing* Hyper-V hypercalls in terms of KVM_EXIT_IO or
KVM_EXIT_MMIO looked hard at best.

> So we should not add a new exit

Why?  VCPU exit codes are not a scarse resource.

> (I suggested elsewhere the existing hyper-v exit)

So far we've envisaged two reasons for VCPU exit related to hyper-v: one
for hyper-v MSRs and the other for hypercalls.  Since there was a
discussion on implementing generic MSR access by Peter we thought it
wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
interfering with the MSR implementation.

Thanks,
Roman.

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Wed, Jan 20, 2016 at 02:59:08PM +0100, Paolo Bonzini wrote:
> >> --- a/Documentation/virtual/kvm/api.txt
> >> +++ b/Documentation/virtual/kvm/api.txt
> >> @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
> >>  event/message pages and to enable/disable SynIC messages/events processing
> >>  in userspace.
> >>
> >> +		/* KVM_EXIT_HYPERV_HCALL */
> >> +		struct {
> >> +			__u64 input;
> >> +			__u64 params[2];
> >> +			__u64 result;
> >> +		} hv_hcall;
> >> +Indicates that the VCPU exits into userspace to process some guest
> >> +Hyper-V hypercalls.
> > 
> > Why introducing this? We already have KVM_EXIT_HYPERCALL, which is
> > exactly the same. AFAIK it's not used at the moment.
> > Additionally, in theory we could have hypercalls handled in
> > userspace for something else except HyperV. And not only for x86.
> 
> Because, as the docs say, we don't want to do that.  We want to use
> KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
> can't do that for compatibility purposes.

I must admit I saw this part in the docs but failed to understand it.

Is it supposed to mean that we want to avoid using hypercalls as a means
of guest communications with the host userspace in general, and use PIO
or MMIO instead, unless hypercalls are mandated by a guest implemenation
we can't affect (as is the case for Hyper-V)?

Because *implementing* Hyper-V hypercalls in terms of KVM_EXIT_IO or
KVM_EXIT_MMIO looked hard at best.

> So we should not add a new exit

Why?  VCPU exit codes are not a scarse resource.

> (I suggested elsewhere the existing hyper-v exit)

So far we've envisaged two reasons for VCPU exit related to hyper-v: one
for hyper-v MSRs and the other for hypercalls.  Since there was a
discussion on implementing generic MSR access by Peter we thought it
wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
interfering with the MSR implementation.

Thanks,
Roman.

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Roman Kagan]

On Wed, Jan 20, 2016 at 02:43:01PM +0100, Paolo Bonzini wrote:
> 
> 
> On 12/01/2016 11:50, Andrey Smetanin wrote:
> > The patch implements KVM_EXIT_HV_HCALL functionality
> > for Hyper-V VMBus hypercalls: HV_X64_HCALL_POST_MESSAGE,
> > HV_X64_HCALL_SIGNAL_EVENT.
> > 
> > Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> > Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> > CC: Gleb Natapov <gleb@kernel.org>
> > CC: Paolo Bonzini <pbonzini@redhat.com>
> > CC: Joerg Roedel <joro@8bytes.org>
> > CC: "K. Y. Srinivasan" <kys@microsoft.com>
> > CC: Haiyang Zhang <haiyangz@microsoft.com>
> > CC: Roman Kagan <rkagan@virtuozzo.com>
> > CC: Denis V. Lunev <den@openvz.org>
> > CC: qemu-devel@nongnu.org
> > ---
> >  Documentation/virtual/kvm/api.txt |  8 ++++++++
> >  arch/x86/kvm/hyperv.c             | 28 +++++++++++++++++++++-------
> >  arch/x86/kvm/hyperv.h             |  1 +
> >  arch/x86/kvm/x86.c                |  3 +++
> >  include/uapi/linux/kvm.h          |  7 +++++++
> >  5 files changed, 40 insertions(+), 7 deletions(-)
> > 
> > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> > index 053f613..23d4b9d 100644
> > --- a/Documentation/virtual/kvm/api.txt
> > +++ b/Documentation/virtual/kvm/api.txt
> > @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
> >  event/message pages and to enable/disable SynIC messages/events processing
> >  in userspace.
> >  
> > +		/* KVM_EXIT_HYPERV_HCALL */
> > +		struct {
> > +			__u64 input;
> > +			__u64 params[2];
> > +			__u64 result;
> > +		} hv_hcall;
> > +Indicates that the VCPU exits into userspace to process some guest
> > +Hyper-V hypercalls.
> 
> Is this something other than KVM_EXIT_HYPERV because of the previous
> discussion about MSRs?  Otherwise, it definitely should be a separate
> type of the existing KVM_EXIT_HYPERV exit.

Mostly.  Besides, it wasn't obvious why we needed another level of
dispatch.

> (In fact, I do not think anymore that I will add the MSR exit in 4.5.
> It's kind of against the KVM design to do "CPU things" outside the
> kernel.  My conjecture is that MSRs are either simple and thus not
> security sensitive, or complicated and thus require state that resides
> in the kernel).
> 
> >  		/* Fix the size of the union. */
> >  		char padding[256];
> >  	};
> > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> > index 0e7c90f..76c9ec4 100644
> > --- a/arch/x86/kvm/hyperv.c
> > +++ b/arch/x86/kvm/hyperv.c
> > @@ -1087,18 +1087,32 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> >  	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
> >  		kvm_vcpu_on_spin(vcpu);
> >  		break;
> > +	case HV_X64_HCALL_POST_MESSAGE:
> > +	case HV_X64_HCALL_SIGNAL_EVENT:
> > +		vcpu->run->exit_reason = KVM_EXIT_HYPERV_HCALL;
> > +		vcpu->run->hv_hcall.input = param;
> > +		vcpu->run->hv_hcall.params[0] = ingpa;
> > +		vcpu->run->hv_hcall.params[1] = outgpa;
> > +		return 0;
> >  	default:
> >  		res = HV_STATUS_INVALID_HYPERCALL_CODE;
> >  		break;
> >  	}
> >  
> >  	ret = res | (((u64)rep_done & 0xfff) << 32);
> > -	if (longmode) {
> > -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret);
> > -	} else {
> > -		kvm_register_write(vcpu, VCPU_REGS_RDX, ret >> 32);
> > -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret & 0xffffffff);
> > -	}
> > -
> > +	kvm_hv_hypercall_set_result(vcpu, ret);
> >  	return 1;
> >  }
> > +
> > +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
> > +{
> > +	bool longmode;
> > +
> > +	longmode = is_64_bit_mode(vcpu);
> > +	if (longmode)
> > +		kvm_register_write(vcpu, VCPU_REGS_RAX, result);
> > +	else {
> > +		kvm_register_write(vcpu, VCPU_REGS_RDX, result >> 32);
> > +		kvm_register_write(vcpu, VCPU_REGS_RAX, result & 0xffffffff);
> > +	}
> > +}
> > diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> > index 60eccd4..64a4a3b 100644
> > --- a/arch/x86/kvm/hyperv.h
> > +++ b/arch/x86/kvm/hyperv.h
> > @@ -52,6 +52,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
> >  
> >  bool kvm_hv_hypercall_enabled(struct kvm *kvm);
> >  int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
> > +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result);
> >  
> >  void kvm_hv_irq_routing_update(struct kvm *kvm);
> >  int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint);
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index fad1d09..6ad3599 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -6886,6 +6886,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> >  	} else
> >  		WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
> >  
> > +	if (unlikely(kvm_run->exit_reason == KVM_EXIT_HYPERV_HCALL))
> > +		kvm_hv_hypercall_set_result(vcpu, kvm_run->hv_hcall.result);
> > +
> >  	r = vcpu_run(vcpu);
> >  
> >  out:
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 9da9051..a62c4fb 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -199,6 +199,7 @@ struct kvm_hyperv_exit {
> >  #define KVM_EXIT_S390_STSI        25
> >  #define KVM_EXIT_IOAPIC_EOI       26
> >  #define KVM_EXIT_HYPERV           27
> > +#define KVM_EXIT_HYPERV_HCALL     28
> >  
> >  /* For KVM_EXIT_INTERNAL_ERROR */
> >  /* Emulate instruction failed. */
> > @@ -355,6 +356,12 @@ struct kvm_run {
> >  		} eoi;
> >  		/* KVM_EXIT_HYPERV */
> >  		struct kvm_hyperv_exit hyperv;
> > +		/* KVM_EXIT_HYPERV_HCALL */
> > +		struct {
> > +			__u64 input;
> > +			__u64 params[2];
> > +			__u64 result;
> 
> Please put result before params, so that it's possible to add more
> parameters in the future.

The number of parameters is fixed in the Hyper-V spec: they are either
physical addresses of the input and output parameter structures, or (for
"fast" hypercalls) up to two input parameters.

That said, there's also another variant called "extended fast
hypercalls" when extra parameters are placed in XMM registers so if we
ever decide to implement those we'll need another field in this
structure, so it indeed looks sensible to swap result and params now.

Thanks,
Roman.

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Roman Kagan]

On Wed, Jan 20, 2016 at 02:43:01PM +0100, Paolo Bonzini wrote:
> 
> 
> On 12/01/2016 11:50, Andrey Smetanin wrote:
> > The patch implements KVM_EXIT_HV_HCALL functionality
> > for Hyper-V VMBus hypercalls: HV_X64_HCALL_POST_MESSAGE,
> > HV_X64_HCALL_SIGNAL_EVENT.
> > 
> > Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
> > Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> > CC: Gleb Natapov <gleb@kernel.org>
> > CC: Paolo Bonzini <pbonzini@redhat.com>
> > CC: Joerg Roedel <joro@8bytes.org>
> > CC: "K. Y. Srinivasan" <kys@microsoft.com>
> > CC: Haiyang Zhang <haiyangz@microsoft.com>
> > CC: Roman Kagan <rkagan@virtuozzo.com>
> > CC: Denis V. Lunev <den@openvz.org>
> > CC: qemu-devel@nongnu.org
> > ---
> >  Documentation/virtual/kvm/api.txt |  8 ++++++++
> >  arch/x86/kvm/hyperv.c             | 28 +++++++++++++++++++++-------
> >  arch/x86/kvm/hyperv.h             |  1 +
> >  arch/x86/kvm/x86.c                |  3 +++
> >  include/uapi/linux/kvm.h          |  7 +++++++
> >  5 files changed, 40 insertions(+), 7 deletions(-)
> > 
> > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> > index 053f613..23d4b9d 100644
> > --- a/Documentation/virtual/kvm/api.txt
> > +++ b/Documentation/virtual/kvm/api.txt
> > @@ -3359,6 +3359,14 @@ Hyper-V SynIC state change. Notification is used to remap SynIC
> >  event/message pages and to enable/disable SynIC messages/events processing
> >  in userspace.
> >  
> > +		/* KVM_EXIT_HYPERV_HCALL */
> > +		struct {
> > +			__u64 input;
> > +			__u64 params[2];
> > +			__u64 result;
> > +		} hv_hcall;
> > +Indicates that the VCPU exits into userspace to process some guest
> > +Hyper-V hypercalls.
> 
> Is this something other than KVM_EXIT_HYPERV because of the previous
> discussion about MSRs?  Otherwise, it definitely should be a separate
> type of the existing KVM_EXIT_HYPERV exit.

Mostly.  Besides, it wasn't obvious why we needed another level of
dispatch.

> (In fact, I do not think anymore that I will add the MSR exit in 4.5.
> It's kind of against the KVM design to do "CPU things" outside the
> kernel.  My conjecture is that MSRs are either simple and thus not
> security sensitive, or complicated and thus require state that resides
> in the kernel).
> 
> >  		/* Fix the size of the union. */
> >  		char padding[256];
> >  	};
> > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> > index 0e7c90f..76c9ec4 100644
> > --- a/arch/x86/kvm/hyperv.c
> > +++ b/arch/x86/kvm/hyperv.c
> > @@ -1087,18 +1087,32 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> >  	case HV_X64_HCALL_NOTIFY_LONG_SPIN_WAIT:
> >  		kvm_vcpu_on_spin(vcpu);
> >  		break;
> > +	case HV_X64_HCALL_POST_MESSAGE:
> > +	case HV_X64_HCALL_SIGNAL_EVENT:
> > +		vcpu->run->exit_reason = KVM_EXIT_HYPERV_HCALL;
> > +		vcpu->run->hv_hcall.input = param;
> > +		vcpu->run->hv_hcall.params[0] = ingpa;
> > +		vcpu->run->hv_hcall.params[1] = outgpa;
> > +		return 0;
> >  	default:
> >  		res = HV_STATUS_INVALID_HYPERCALL_CODE;
> >  		break;
> >  	}
> >  
> >  	ret = res | (((u64)rep_done & 0xfff) << 32);
> > -	if (longmode) {
> > -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret);
> > -	} else {
> > -		kvm_register_write(vcpu, VCPU_REGS_RDX, ret >> 32);
> > -		kvm_register_write(vcpu, VCPU_REGS_RAX, ret & 0xffffffff);
> > -	}
> > -
> > +	kvm_hv_hypercall_set_result(vcpu, ret);
> >  	return 1;
> >  }
> > +
> > +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
> > +{
> > +	bool longmode;
> > +
> > +	longmode = is_64_bit_mode(vcpu);
> > +	if (longmode)
> > +		kvm_register_write(vcpu, VCPU_REGS_RAX, result);
> > +	else {
> > +		kvm_register_write(vcpu, VCPU_REGS_RDX, result >> 32);
> > +		kvm_register_write(vcpu, VCPU_REGS_RAX, result & 0xffffffff);
> > +	}
> > +}
> > diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> > index 60eccd4..64a4a3b 100644
> > --- a/arch/x86/kvm/hyperv.h
> > +++ b/arch/x86/kvm/hyperv.h
> > @@ -52,6 +52,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
> >  
> >  bool kvm_hv_hypercall_enabled(struct kvm *kvm);
> >  int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
> > +void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result);
> >  
> >  void kvm_hv_irq_routing_update(struct kvm *kvm);
> >  int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vcpu_id, u32 sint);
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index fad1d09..6ad3599 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -6886,6 +6886,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> >  	} else
> >  		WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
> >  
> > +	if (unlikely(kvm_run->exit_reason == KVM_EXIT_HYPERV_HCALL))
> > +		kvm_hv_hypercall_set_result(vcpu, kvm_run->hv_hcall.result);
> > +
> >  	r = vcpu_run(vcpu);
> >  
> >  out:
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 9da9051..a62c4fb 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -199,6 +199,7 @@ struct kvm_hyperv_exit {
> >  #define KVM_EXIT_S390_STSI        25
> >  #define KVM_EXIT_IOAPIC_EOI       26
> >  #define KVM_EXIT_HYPERV           27
> > +#define KVM_EXIT_HYPERV_HCALL     28
> >  
> >  /* For KVM_EXIT_INTERNAL_ERROR */
> >  /* Emulate instruction failed. */
> > @@ -355,6 +356,12 @@ struct kvm_run {
> >  		} eoi;
> >  		/* KVM_EXIT_HYPERV */
> >  		struct kvm_hyperv_exit hyperv;
> > +		/* KVM_EXIT_HYPERV_HCALL */
> > +		struct {
> > +			__u64 input;
> > +			__u64 params[2];
> > +			__u64 result;
> 
> Please put result before params, so that it's possible to add more
> parameters in the future.

The number of parameters is fixed in the Hyper-V spec: they are either
physical addresses of the input and output parameter structures, or (for
"fast" hypercalls) up to two input parameters.

That said, there's also another variant called "extended fast
hypercalls" when extra parameters are placed in XMM registers so if we
ever decide to implement those we'll need another field in this
structure, so it indeed looks sensible to swap result and params now.

Thanks,
Roman.

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 20/01/2016 16:20, 'Roman Kagan' wrote:
>> > Because, as the docs say, we don't want to do that.  We want to use
>> > KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
>> > can't do that for compatibility purposes.
> I must admit I saw this part in the docs but failed to understand it.
> 
> Is it supposed to mean that we want to avoid using hypercalls as a means
> of guest communications with the host userspace in general, and use PIO
> or MMIO instead, unless hypercalls are mandated by a guest implemenation
> we can't affect (as is the case for Hyper-V)?

In this case we use hypercalls. :)

However, we use a separate exit instead of putting everything under
KVM_EXIT_HYPERCALL.  This, as you mentioned, has the advantage that you
can customize it according to the calling convention (which may help
avoiding TOCTTOU issues, too).

> Because *implementing* Hyper-V hypercalls in terms of KVM_EXIT_IO or
> KVM_EXIT_MMIO looked hard at best.
> 
>> > So we should not add a new exit
> Why?  VCPU exit codes are not a scarse resource.

Indeed, but grouping makes things easier to understand.

> So far we've envisaged two reasons for VCPU exit related to hyper-v: one
> for hyper-v MSRs and the other for hypercalls.  Since there was a
> discussion on implementing generic MSR access by Peter we thought it
> wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
> interfering with the MSR implementation.

That's a good idea.  However, I think I'm not going to accept the MSR
exit feature, and then the current Hyper-V exit API makes some sense
indeed (it's just 3 values, transferring them all at once is not
expensive at all).

Paolo

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 20/01/2016 16:20, 'Roman Kagan' wrote:
>> > Because, as the docs say, we don't want to do that.  We want to use
>> > KVM_EXIT_IO or KVM_EXIT_MMIO, with two exceptions: s390 and wherever we
>> > can't do that for compatibility purposes.
> I must admit I saw this part in the docs but failed to understand it.
> 
> Is it supposed to mean that we want to avoid using hypercalls as a means
> of guest communications with the host userspace in general, and use PIO
> or MMIO instead, unless hypercalls are mandated by a guest implemenation
> we can't affect (as is the case for Hyper-V)?

In this case we use hypercalls. :)

However, we use a separate exit instead of putting everything under
KVM_EXIT_HYPERCALL.  This, as you mentioned, has the advantage that you
can customize it according to the calling convention (which may help
avoiding TOCTTOU issues, too).

> Because *implementing* Hyper-V hypercalls in terms of KVM_EXIT_IO or
> KVM_EXIT_MMIO looked hard at best.
> 
>> > So we should not add a new exit
> Why?  VCPU exit codes are not a scarse resource.

Indeed, but grouping makes things easier to understand.

> So far we've envisaged two reasons for VCPU exit related to hyper-v: one
> for hyper-v MSRs and the other for hypercalls.  Since there was a
> discussion on implementing generic MSR access by Peter we thought it
> wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
> interfering with the MSR implementation.

That's a good idea.  However, I think I'm not going to accept the MSR
exit feature, and then the current Hyper-V exit API makes some sense
indeed (it's just 3 values, transferring them all at once is not
expensive at all).

Paolo

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Wed, Jan 20, 2016 at 06:02:25PM +0100, Paolo Bonzini wrote:
> 
> 
> On 20/01/2016 16:20, 'Roman Kagan' wrote:
> >> > So we should not add a new exit
> > Why?  VCPU exit codes are not a scarse resource.
> 
> Indeed, but grouping makes things easier to understand.
> 
> > So far we've envisaged two reasons for VCPU exit related to hyper-v: one
> > for hyper-v MSRs and the other for hypercalls.  Since there was a
> > discussion on implementing generic MSR access by Peter we thought it
> > wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
> > interfering with the MSR implementation.
> 
> That's a good idea.  However, I think I'm not going to accept the MSR
> exit feature, and then the current Hyper-V exit API makes some sense
> indeed (it's just 3 values, transferring them all at once is not
> expensive at all).

OK can we please sum up (as I'm now a bit confused) what we do now:

1) use a single vcpu exit for both Hyper-V cases (which implies we need
   to fix this patchset to add the subcode for hypercalls)

 or

2) use individual vcpu exits for Hyper-V MSRs and for Hyper-V hypercalls
   (which implies we need to submit an incremental patch dropping the
   subcode from Hyper-V MSR exit and renaming it to better describe the
   reality)?

Thanks,
Roman.

Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

['Roman Kagan']

On Wed, Jan 20, 2016 at 06:02:25PM +0100, Paolo Bonzini wrote:
> 
> 
> On 20/01/2016 16:20, 'Roman Kagan' wrote:
> >> > So we should not add a new exit
> > Why?  VCPU exit codes are not a scarse resource.
> 
> Indeed, but grouping makes things easier to understand.
> 
> > So far we've envisaged two reasons for VCPU exit related to hyper-v: one
> > for hyper-v MSRs and the other for hypercalls.  Since there was a
> > discussion on implementing generic MSR access by Peter we thought it
> > wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
> > interfering with the MSR implementation.
> 
> That's a good idea.  However, I think I'm not going to accept the MSR
> exit feature, and then the current Hyper-V exit API makes some sense
> indeed (it's just 3 values, transferring them all at once is not
> expensive at all).

OK can we please sum up (as I'm now a bit confused) what we do now:

1) use a single vcpu exit for both Hyper-V cases (which implies we need
   to fix this patchset to add the subcode for hypercalls)

 or

2) use individual vcpu exits for Hyper-V MSRs and for Hyper-V hypercalls
   (which implies we need to submit an incremental patch dropping the
   subcode from Hyper-V MSR exit and renaming it to better describe the
   reality)?

Thanks,
Roman.

Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 20/01/2016 18:31, 'Roman Kagan' wrote:
> On Wed, Jan 20, 2016 at 06:02:25PM +0100, Paolo Bonzini wrote:
>>
>>
>> On 20/01/2016 16:20, 'Roman Kagan' wrote:
>>>>> So we should not add a new exit
>>> Why?  VCPU exit codes are not a scarse resource.
>>
>> Indeed, but grouping makes things easier to understand.
>>
>>> So far we've envisaged two reasons for VCPU exit related to hyper-v: one
>>> for hyper-v MSRs and the other for hypercalls.  Since there was a
>>> discussion on implementing generic MSR access by Peter we thought it
>>> wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
>>> interfering with the MSR implementation.
>>
>> That's a good idea.  However, I think I'm not going to accept the MSR
>> exit feature, and then the current Hyper-V exit API makes some sense
>> indeed (it's just 3 values, transferring them all at once is not
>> expensive at all).
> 
> OK can we please sum up (as I'm now a bit confused) what we do now:
> 
> 1) use a single vcpu exit for both Hyper-V cases (which implies we need
>    to fix this patchset to add the subcode for hypercalls)

This.

Paolo

>  or
> 
> 2) use individual vcpu exits for Hyper-V MSRs and for Hyper-V hypercalls
>    (which implies we need to submit an incremental patch dropping the
>    subcode from Hyper-V MSR exit and renaming it to better describe the
>    reality)?
> 
> Thanks,
> Roman.
> --
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Re: [Qemu-devel] [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit

[Paolo Bonzini]

On 20/01/2016 18:31, 'Roman Kagan' wrote:
> On Wed, Jan 20, 2016 at 06:02:25PM +0100, Paolo Bonzini wrote:
>>
>>
>> On 20/01/2016 16:20, 'Roman Kagan' wrote:
>>>>> So we should not add a new exit
>>> Why?  VCPU exit codes are not a scarse resource.
>>
>> Indeed, but grouping makes things easier to understand.
>>
>>> So far we've envisaged two reasons for VCPU exit related to hyper-v: one
>>> for hyper-v MSRs and the other for hypercalls.  Since there was a
>>> discussion on implementing generic MSR access by Peter we thought it
>>> wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid
>>> interfering with the MSR implementation.
>>
>> That's a good idea.  However, I think I'm not going to accept the MSR
>> exit feature, and then the current Hyper-V exit API makes some sense
>> indeed (it's just 3 values, transferring them all at once is not
>> expensive at all).
> 
> OK can we please sum up (as I'm now a bit confused) what we do now:
> 
> 1) use a single vcpu exit for both Hyper-V cases (which implies we need
>    to fix this patchset to add the subcode for hypercalls)

This.

Paolo

>  or
> 
> 2) use individual vcpu exits for Hyper-V MSRs and for Hyper-V hypercalls
>    (which implies we need to submit an incremental patch dropping the
>    subcode from Hyper-V MSR exit and renaming it to better describe the
>    reality)?
> 
> Thanks,
> Roman.
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