FAILED: Patch "crypto: virtio: Add spinlock protection with virtqueue notification" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From af9a17d29ce9060664f56264bcc64b976fddd2b5 Mon Sep 17 00:00:00 2001
From: Bibo Mao <maobibo@loongson.cn>
Date: Tue, 13 Jan 2026 11:05:54 +0800
Subject: [PATCH] crypto: virtio: Add spinlock protection with virtqueue
 notification

When VM boots with one virtio-crypto PCI device and builtin backend,
run openssl benchmark command with multiple processes, such as
  openssl speed -evp aes-128-cbc -engine afalg  -seconds 10 -multi 32

openssl processes will hangup and there is error reported like this:
 virtio_crypto virtio0: dataq.0:id 3 is not a head!

It seems that the data virtqueue need protection when it is handled
for virtio done notification. If the spinlock protection is added
in virtcrypto_done_task(), openssl benchmark with multiple processes
works well.

Fixes: fed93fb62e05 ("crypto: virtio - Handle dataq logic with tasklet")
Cc: stable@vger.kernel.org
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260113030556.3522533-2-maobibo@loongson.cn>
---
 drivers/crypto/virtio/virtio_crypto_core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/crypto/virtio/virtio_crypto_core.c b/drivers/crypto/virtio/virtio_crypto_core.c
index 3d241446099cc..ccc6b5c1b24b3 100644
--- a/drivers/crypto/virtio/virtio_crypto_core.c
+++ b/drivers/crypto/virtio/virtio_crypto_core.c
@@ -75,15 +75,20 @@ static void virtcrypto_done_task(unsigned long data)
 	struct data_queue *data_vq = (struct data_queue *)data;
 	struct virtqueue *vq = data_vq->vq;
 	struct virtio_crypto_request *vc_req;
+	unsigned long flags;
 	unsigned int len;
 
+	spin_lock_irqsave(&data_vq->lock, flags);
 	do {
 		virtqueue_disable_cb(vq);
 		while ((vc_req = virtqueue_get_buf(vq, &len)) != NULL) {
+			spin_unlock_irqrestore(&data_vq->lock, flags);
 			if (vc_req->alg_cb)
 				vc_req->alg_cb(vc_req, len);
+			spin_lock_irqsave(&data_vq->lock, flags);
 		}
 	} while (!virtqueue_enable_cb(vq));
+	spin_unlock_irqrestore(&data_vq->lock, flags);
 }
 
 static void virtcrypto_dataq_callback(struct virtqueue *vq)
-- 
2.51.0