linux-kernel - [PATCH v2 2/6] Drivers: hv: Use nested hypercall for post message and signal event

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Message-Id: <1751582677-30930-3-git-send-email-nunodasneves@linux.microsoft.com>
Date: Thu,  3 Jul 2025 15:44:33 -0700
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: linux-hyperv@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
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	Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Subject: [PATCH v2 2/6] Drivers: hv: Use nested hypercall for post message and signal event

When running nested, these hypercalls must be sent to the L0 hypervisor
or VMBus will fail.

Remove hv_do_nested_hypercall() and hv_do_fast_nested_hypercall8()
altogether and open-code these cases, since there are only 2 and all
they do is add the nested bit.

Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Reviewed-by: Roman Kisel <romank@...ux.microsoft.com>
---
 arch/x86/include/asm/mshyperv.h | 20 --------------------
 drivers/hv/connection.c         |  7 +++++--
 drivers/hv/hv.c                 |  6 ++++--
 3 files changed, 9 insertions(+), 24 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 5ec92e3e2e37..e00a8431ef8e 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -111,12 +111,6 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
 	return hv_status;
 }
 
-/* Hypercall to the L0 hypervisor */
-static inline u64 hv_do_nested_hypercall(u64 control, void *input, void *output)
-{
-	return hv_do_hypercall(control | HV_HYPERCALL_NESTED, input, output);
-}
-
 /* Fast hypercall with 8 bytes of input and no output */
 static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
 {
@@ -164,13 +158,6 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
 	return _hv_do_fast_hypercall8(control, input1);
 }
 
-static inline u64 hv_do_fast_nested_hypercall8(u16 code, u64 input1)
-{
-	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED;
-
-	return _hv_do_fast_hypercall8(control, input1);
-}
-
 /* Fast hypercall with 16 bytes of input */
 static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 input2)
 {
@@ -222,13 +209,6 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
 	return _hv_do_fast_hypercall16(control, input1, input2);
 }
 
-static inline u64 hv_do_fast_nested_hypercall16(u16 code, u64 input1, u64 input2)
-{
-	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED;
-
-	return _hv_do_fast_hypercall16(control, input1, input2);
-}
-
 extern struct hv_vp_assist_page **hv_vp_assist_page;
 
 static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned int cpu)
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index be490c598785..47c93cee1ef6 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -518,8 +518,11 @@ void vmbus_set_event(struct vmbus_channel *channel)
 					 channel->sig_event, 0);
 		else
 			WARN_ON_ONCE(1);
-	} else {
-		hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
+	} else if (hv_nested) {
+		u64 control = HVCALL_SIGNAL_EVENT;
+
+		control |= hv_nested ? HV_HYPERCALL_NESTED : 0;
+		hv_do_fast_hypercall8(control, channel->sig_event);
 	}
 }
 EXPORT_SYMBOL_GPL(vmbus_set_event);
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 308c8f279df8..b14c5f9e0ef2 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -85,8 +85,10 @@ int hv_post_message(union hv_connection_id connection_id,
 		else
 			status = HV_STATUS_INVALID_PARAMETER;
 	} else {
-		status = hv_do_hypercall(HVCALL_POST_MESSAGE,
-					 aligned_msg, NULL);
+		u64 control = HVCALL_POST_MESSAGE;
+
+		control |= hv_nested ? HV_HYPERCALL_NESTED : 0;
+		status = hv_do_hypercall(control, aligned_msg, NULL);
 	}
 
 	local_irq_restore(flags);
-- 
2.34.1