linux-kernel - [PATCH] misc: fastrpc: copy to user only for non-DMA-BUF heap buffers

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Date:   Thu, 23 Sep 2021 14:07:52 +0530
From:   Jeya R <jeyr@...eaurora.org>
To:     linux-arm-msm@...r.kernel.org, srinivas.kandagatla@...aro.org
Cc:     Jeya R <jeyr@...eaurora.org>, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, fastrpc.upstream@....qualcomm.com
Subject: [PATCH] misc: fastrpc: copy to user only for non-DMA-BUF heap buffers

fastrpc_put_args is copying all the output buffers to user. For large
number of output context buffers, this might cause performance
degradation. Copying is not needed for DMA-BUF heap buffers.

Signed-off-by: Jeya R <jeyr@...eaurora.org>
---
 drivers/misc/fastrpc.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index beda610..536eabf 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -890,15 +890,17 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx,
 	inbufs = REMOTE_SCALARS_INBUFS(ctx->sc);
 
 	for (i = inbufs; i < ctx->nbufs; ++i) {
-		void *src = (void *)(uintptr_t)rpra[i].pv;
-		void *dst = (void *)(uintptr_t)ctx->args[i].ptr;
-		u64 len = rpra[i].len;
+		if (!ctx->maps[i]) {
+			void *src = (void *)(uintptr_t)rpra[i].pv;
+			void *dst = (void *)(uintptr_t)ctx->args[i].ptr;
+			u64 len = rpra[i].len;
 
-		if (!kernel) {
-			if (copy_to_user((void __user *)dst, src, len))
-				return -EFAULT;
-		} else {
-			memcpy(dst, src, len);
+			if (!kernel) {
+				if (copy_to_user((void __user *)dst, src, len))
+					return -EFAULT;
+			} else {
+				memcpy(dst, src, len);
+			}
 		}
 	}
 
-- 
2.7.4