gpu: nvgpu: recover on first interrupt reported for mmu nack

In case of mmu nack error interrupt is received twice through SM
reported mmu nack interrupt and mmu fault in undertermined order.
Recover on the first received interrupt to avoid semaphore release
and skip doing a second recovery.

Also fix NULL pointer dereference in function
gv11b_fifo_reset_pbdma_and_eng_faulted when channel reference is
invalid in teardown path.

Bug 200382235

Change-Id: I361a5725d7b6355ebf02b2870727f647fbd7a37e
Signed-off-by: Aparna Das <aparnad@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1739804
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

1 files changed, 21 insertions, 14 deletions

diff --git a/drivers/gpu/nvgpu/gv11b/gr_gv11b.c b/drivers/gpu/nvgpu/gv11b/gr_gv11b.c
index 694ff8ad..aed45ceb 100644
--- a/drivers/gpu/nvgpu/gv11b/gr_gv11b.c
+++ b/drivers/gpu/nvgpu/gv11b/gr_gv11b.c
@@ -2093,23 +2093,30 @@ static int gr_gv11b_handle_warp_esr_error_mmu_nack(struct gk20a *g,
         u32 warp_esr_error,
         struct channel_gk20a *fault_ch)
 {
-        struct tsg_gk20a *tsg;
         u32 offset;
+        int err = 0;
 
+        fault_ch = gk20a_channel_get(fault_ch);
         if (fault_ch) {
-                tsg = &g->fifo.tsg[fault_ch->tsgid];
-
-                /*
-                 * Upon receiving MMU_FAULT error, MMU will forward MMU_NACK
-                 * to SM. So MMU_FAULT handling path will take care of
-                 * triggering RC recovery
-                 *
-                 * In MMU_NACK handling path, we just set the error notifier
-                 * and clear the interrupt so that the User Space sees the error
-                 * as soon as semaphores are released by SM
-                 */
-                gk20a_fifo_set_ctx_mmu_error_tsg(g, tsg);
+                if (!fault_ch->mmu_nack_handled) {
+                        /* recovery is not done for the channel implying mmu
+                         * nack interrupt is serviced before mmu fault. Force
+                         * recovery by returning an error. Also indicate we
+                         * should skip a second recovery.
+                         */
+                        fault_ch->mmu_nack_handled = true;
+                        err = -EFAULT;
+                }
         }
+        /* else mmu fault is serviced first and channel is closed */
+
+        /* do not release reference to ch as we do not want userspace to close
+         * this channel on recovery. Otherwise mmu fault handler will enter
+         * recovery path even if channel is invalid. We want to explicitly check
+         * for teardown value in mmu fault handler.
+         */
+        if (!err)
+                gk20a_channel_put(fault_ch);
 
         /* clear interrupt */
         offset = gk20a_gr_gpc_offset(g, gpc) +
@@ -2122,7 +2129,7 @@ static int gr_gv11b_handle_warp_esr_error_mmu_nack(struct gk20a *g,
                         "ESR %s(0x%x)",
                         "MMU NACK ERROR",
                         warp_esr_error);
-        return 0;
+        return err;
 }
 
 static bool gr_gv11b_check_warp_esr_error(struct gk20a *g, u32 warp_esr_error)