From 1b136b50e07c1c3678dce710875cb8e5ddff7904 Mon Sep 17 00:00:00 2001
From: Ved Shanbhogue <ved@rivosinc.com>
Date: Mon, 1 Jul 2024 10:13:51 -0500
Subject: [PATCH] Defer cqon clearing if a iofence is pending

---
 .../libiommu/src/iommu_command_queue.c        |  6 +++
 iommu_ref_model/libiommu/src/iommu_reg.c      | 13 +++--
 iommu_ref_model/test/test_app.c               | 54 +++++++++++++++++++
 3 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/iommu_ref_model/libiommu/src/iommu_command_queue.c b/iommu_ref_model/libiommu/src/iommu_command_queue.c
index 0f5aa3cd..a2a535b1 100644
--- a/iommu_ref_model/libiommu/src/iommu_command_queue.c
+++ b/iommu_ref_model/libiommu/src/iommu_command_queue.c
@@ -513,6 +513,12 @@ do_pending_iofence() {
         g_reg_file.cqh.index =
             (g_reg_file.cqh.index + 1) & ((1UL << (g_reg_file.cqb.log2szm1 + 1)) - 1);
     }
+    // If IOFENCE is not pending and CQ was requested to be
+    // turned off then turn it off now
+    if ( g_iofence_wait_pending_inv == 0 ) {
+        g_reg_file.cqcsr.cqon = g_reg_file.cqcsr.cqen;
+        g_reg_file.cqcsr.busy = 0;
+    }
     return;
 }
 void
diff --git a/iommu_ref_model/libiommu/src/iommu_reg.c b/iommu_ref_model/libiommu/src/iommu_reg.c
index 978ef9a5..041cb3ca 100644
--- a/iommu_ref_model/libiommu/src/iommu_reg.c
+++ b/iommu_ref_model/libiommu/src/iommu_reg.c
@@ -19,6 +19,7 @@ uint8_t g_fctl_be_writeable;
 uint8_t g_max_iommu_mode;
 uint8_t g_fill_ats_trans_in_ioatc;
 uint32_t g_max_devid_mask;
+extern uint8_t g_iofence_wait_pending_inv;
 
 uint8_t
 is_access_valid(
@@ -352,8 +353,12 @@ write_register(
                 }
                 if ( cqcsr_temp.cqen == 0 ) {
                     // mark queue as being off
-                    g_reg_file.cqcsr.cqon = 0;
                     g_reg_file.cqcsr.cqen = 0;
+                    // If IOFENCE is waiting then CQ stays active
+                    // through the wait
+                    if ( g_iofence_wait_pending_inv == 0 ) {
+                        g_reg_file.cqcsr.cqon = 0;
+                    }
                 }
             }
             // Command-queue-interrupt-enable bit enables
@@ -367,8 +372,10 @@ write_register(
             if ( cqcsr_temp.cmd_ill == 1 )    g_reg_file.cqcsr.cmd_ill = 0;
             if ( cqcsr_temp.fence_w_ip == 1 ) g_reg_file.cqcsr.fence_w_ip = 0;
 
-            // Clear the busy bit
-            g_reg_file.cqcsr.busy = 0;
+            // Clear the busy bit. The busy bit may stay active
+            // if an IOFENCE is pending
+            if ( g_reg_file.cqcsr.cqen == g_reg_file.cqcsr.cqon )
+                g_reg_file.cqcsr.busy = 0;
             return;
         case FQCSR_OFFSET:
             // Write to `fqcsr` may require the IOMMU to perform
diff --git a/iommu_ref_model/test/test_app.c b/iommu_ref_model/test/test_app.c
index 00bb9618..8ceb3f92 100644
--- a/iommu_ref_model/test/test_app.c
+++ b/iommu_ref_model/test/test_app.c
@@ -3324,6 +3324,60 @@ main(void) {
     // Complete next two
     inv_cc.PAYLOAD = (0x1234UL << 48UL) | (1UL << 32UL) | 0x00000003UL;
     fail_if( ( handle_invalidation_completion(&inv_cc) != 0 ) );
+
+    // Test turning off command queue while IOFENCE is pending
+    // send one - itag should be 0
+    exp_msg.MSGCODE = INVAL_REQ_MSG_CODE;
+    exp_msg.TAG = 0;
+    exp_msg.RID = 0x1234;
+    exp_msg.PV = 0;
+    exp_msg.PID = 0;
+    exp_msg.PRIV = 0;
+    exp_msg.EXEC_REQ = 0;
+    exp_msg.DSV = 1;
+    exp_msg.DSEG = 0x43;
+    exp_msg.PAYLOAD = 0x1234000000000000;
+    message_received = 0;
+    ats_command(INVAL, 1, 0, 0, 0x43, 0x1234, 0x1234000000000000);
+    fail_if( ( message_received == 0 ) );
+    fail_if( ( exp_msg_received == 0 ) );
+
+    // Fence it - fence should block
+    iofence_PPN = get_free_ppn(1);
+    iofence_data = 0x1234567812345678;
+    write_memory((char *)&iofence_data, (iofence_PPN * PAGESIZE), 8);
+    pr_go_requested = 0;
+    pw_go_requested = 0;
+    iofence(IOFENCE_C, 1, 1, 1, 0, (iofence_PPN * PAGESIZE), 0xDEADBEEF);
+    // Fence should not complete
+    read_memory((iofence_PPN * PAGESIZE), 8, (char *)&iofence_data);
+    fail_if( ( iofence_data != 0x1234567812345678 )  );
+    fail_if( ( pr_go_requested == 1) );
+    fail_if( ( pw_go_requested == 1) );
+
+    cqcsr.raw = read_register(CQCSR_OFFSET, 4);
+    cqcsr.cqen = 0;
+    write_register(CQCSR_OFFSET, 4, cqcsr.raw);
+
+    cqcsr.raw = read_register(CQCSR_OFFSET, 4);
+    fail_if( ( cqcsr.cqon != 1 ) );
+    fail_if( ( cqcsr.cqen != 0 ) );
+    fail_if( ( cqcsr.busy != 1 ) );
+
+    // Make it timeout
+    do_ats_timer_expiry(0x00000001);
+
+    cqcsr.raw = read_register(CQCSR_OFFSET, 4);
+    fail_if( ( cqcsr.cqon != 0 ) );
+    fail_if( ( cqcsr.cqen != 0 ) );
+    fail_if( ( cqcsr.busy != 0 ) );
+
+    cqcsr.cqen = 1;
+    cqcsr.cmd_to = 1;
+    write_register(CQCSR_OFFSET, 4, cqcsr.raw);
+    cqcsr.raw = read_register(CQCSR_OFFSET, 4);
+    i = read_register(CQH_OFFSET, 4);
+    write_register(CQT_OFFSET, 4, i);
     END_TEST();
 
     START_TEST("MSI write-through mode");