linux-kernel - [PATCH hyperv-next v4 07/16] Drivers: hv: Post messages through the confidential VMBus if available

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Message-ID: <20250714221545.5615-8-romank@linux.microsoft.com>
Date: Mon, 14 Jul 2025 15:15:36 -0700
From: Roman Kisel <romank@...ux.microsoft.com>
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Subject: [PATCH hyperv-next v4 07/16] Drivers: hv: Post messages through the confidential VMBus if available

When the confidential VMBus is available, the guest should post
messages to the paravisor.

Update hv_post_message() to post messages to the paravisor rather than
through GHCB or TD calls.

Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
---
 drivers/hv/hv.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index e9ee0177d765..816f8a14ff63 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -74,7 +74,11 @@ int hv_post_message(union hv_connection_id connection_id,
 	aligned_msg->payload_size = payload_size;
 	memcpy((void *)aligned_msg->payload, payload, payload_size);
 
-	if (ms_hyperv.paravisor_present) {
+	if (ms_hyperv.paravisor_present && !vmbus_is_confidential()) {
+		/*
+		 * If the VMBus isn't confidential, use the CoCo-specific
+		 * mechanism to communicate with the hypervisor.
+		 */
 		if (hv_isolation_type_tdx())
 			status = hv_tdx_hypercall(HVCALL_POST_MESSAGE,
 						  virt_to_phys(aligned_msg), 0);
@@ -85,6 +89,11 @@ int hv_post_message(union hv_connection_id connection_id,
 		else
 			status = HV_STATUS_INVALID_PARAMETER;
 	} else {
+		/*
+		 * If there is no paravisor, this will go to the hypervisor.
+		 * In the Confidential VMBus case, there is the paravisor
+		 * to which this will trap.
+		 */
 		status = hv_do_hypercall(HVCALL_POST_MESSAGE,
 					 aligned_msg, NULL);
 	}
-- 
2.43.0