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 <[email protected]>
Reviewed-by: Tianyu Lan <[email protected]>
Reviewed-by: Michael Kelley <[email protected]>
---
 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 90db1e17582d..b1085473778c 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);
@@ -88,6 +92,11 @@ int hv_post_message(union hv_connection_id connection_id,
                u64 control = HVCALL_POST_MESSAGE;
 
                control |= hv_nested ? HV_HYPERCALL_NESTED : 0;
+               /*
+                * 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(control, aligned_msg, NULL);
        }
 
-- 
2.43.0


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