# \[PATCH\] vhost: reduce stack usage in log\_used

- From: Li Wang \<hidden\>
- Date: 2020-09-11 15:16:40 
- List: netdev
- Page: https://ratatoskr.run/netdev/2020/09/6102037
- Thread: https://ratatoskr.run/kvm/2020/09/6102037/t.md

```text
Fix the warning: [-Werror=-Wframe-larger-than=]

drivers/vhost/vhost.c: In function log_used:
drivers/vhost/vhost.c:1906:1:
warning: the frame size of 1040 bytes is larger than 1024 bytes

Signed-off-by: Li Wang <redacted>
---
 drivers/vhost/vhost.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index b45519c..41769de 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1884,25 +1884,31 @@ static int log_write_hva(struct vhost_virtqueue *vq, u64 hva, u64 len)
 
 static int log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
 {
-	struct iovec iov[64];
+	struct iovec *iov;
 	int i, ret;
 
 	if (!vq->iotlb)
 		return log_write(vq->log_base, vq->log_addr + used_offset, len);
 
+	iov = kcalloc(64, sizeof(*iov), GFP_KERNEL);
+	if (!iov)
+		return -ENOMEM;
+
 	ret = translate_desc(vq, (uintptr_t)vq->used + used_offset,
 			     len, iov, 64, VHOST_ACCESS_WO);
 	if (ret < 0)
-		return ret;
+		goto out;
 
 	for (i = 0; i < ret; i++) {
 		ret = log_write_hva(vq,	(uintptr_t)iov[i].iov_base,
 				    iov[i].iov_len);
 		if (ret)
-			return ret;
+			goto out;
 	}
 
-	return 0;
+out:
+	kfree(iov);
+	return ret;
 }
 
 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
-- 
2.7.4

```