linux-kernel - [PATCH hyperv-next v3 13/15] Drivers: hv: Support confidential VMBus channels

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Message-ID: <20250604004341.7194-14-romank@linux.microsoft.com>
Date: Tue,  3 Jun 2025 17:43:39 -0700
From: Roman Kisel <romank@...ux.microsoft.com>
To: alok.a.tiwari@...cle.com,
	arnd@...db.de,
	bp@...en8.de,
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	dave.hansen@...ux.intel.com,
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Subject: [PATCH hyperv-next v3 13/15] Drivers: hv: Support confidential VMBus channels

To run a confidential VMBus channels, one has to initialize the
co_ring_buffers and co_external_memory fields of the channel
structure.

Advertise support upon negoatiating the version and compute
values for those fields and initialize them.

Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
---
 drivers/hv/channel_mgmt.c | 19 +++++++++++++++++++
 drivers/hv/connection.c   |  3 +++
 2 files changed, 22 insertions(+)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index ca2fe10c110a..33bc29e826bd 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -1021,6 +1021,7 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 	struct vmbus_channel_offer_channel *offer;
 	struct vmbus_channel *oldchannel, *newchannel;
 	size_t offer_sz;
+	bool co_ring_buffer, co_external_memory;
 
 	offer = (struct vmbus_channel_offer_channel *)hdr;
 
@@ -1033,6 +1034,22 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 		return;
 	}
 
+	co_ring_buffer = is_co_ring_buffer(offer);
+	if (co_ring_buffer) {
+		if (vmbus_proto_version < VERSION_WIN10_V6_0 || !vmbus_is_confidential()) {
+			atomic_dec(&vmbus_connection.offer_in_progress);
+			return;
+		}
+	}
+
+	co_external_memory = is_co_external_memory(offer);
+	if (is_co_external_memory(offer)) {
+		if (vmbus_proto_version < VERSION_WIN10_V6_0 || !vmbus_is_confidential()) {
+			atomic_dec(&vmbus_connection.offer_in_progress);
+			return;
+		}
+	}
+
 	oldchannel = find_primary_channel_by_offer(offer);
 
 	if (oldchannel != NULL) {
@@ -1111,6 +1128,8 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 		pr_err("Unable to allocate channel object\n");
 		return;
 	}
+	newchannel->co_ring_buffer = co_ring_buffer;
+	newchannel->co_external_memory = co_external_memory;
 
 	vmbus_setup_channel_state(newchannel, offer);
 
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index be490c598785..eeb472019d69 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -105,6 +105,9 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
 		vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
 	}
 
+	if (vmbus_is_confidential() && version >= VERSION_WIN10_V6_0)
+		msg->feature_flags = VMBUS_FEATURE_FLAG_CONFIDENTIAL_CHANNELS;
+
 	/*
 	 * shared_gpa_boundary is zero in non-SNP VMs, so it's safe to always
 	 * bitwise OR it
-- 
2.43.0