Subject: [PATCH net-next 01/11] net: ethtool: let drivers remove lost RSS contexts

From: Jakub Kicinski <[email-masked]>
Date: Tue, 2 Jul 2024 16:47:46 -0700

RSS contexts may get lost from a device, in various extreme circumstances.
Specifically if the firmware leaks resources and resets, or crashes and
either recovers in partially working state or the crash causes a
different FW version to run - creating the context again may fail.

Drivers should do their absolute best to prevent this from happening.
When it does, however, telling user that a context exists, when it can't
possibly be used any more is counter productive. Add a helper for
drivers to discard contexts. Print an error, in the future netlink
notification will also be sent.

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 include/linux/ethtool.h |  2 ++
 net/ethtool/rss.c       | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index f74bb0cf8ed1..3ce5be0d168a 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -210,6 +210,8 @@ static inline size_t ethtool_rxfh_context_size(u32 indir_size, u32 key_size,
 	return struct_size_t(struct ethtool_rxfh_context, data, flex_len);
 }
 
+void ethtool_rxfh_context_lost(struct net_device *dev, u32 context_id);
+
 /* declare a link mode bitmap */
 #define __ETHTOOL_DECLARE_LINK_MODE_MASK(name)		\
 	DECLARE_BITMAP(name, __ETHTOOL_LINK_MODE_MASK_NBITS)
diff --git a/net/ethtool/rss.c b/net/ethtool/rss.c
index 71679137eff2..e2e5bab56a6b 100644
--- a/net/ethtool/rss.c
+++ b/net/ethtool/rss.c
@@ -159,3 +159,17 @@ const struct ethnl_request_ops ethnl_rss_request_ops = {
 	.fill_reply		= rss_fill_reply,
 	.cleanup_data		= rss_cleanup_data,
 };
+
+void ethtool_rxfh_context_lost(struct net_device *dev, u32 context_id)
+{
+	struct ethtool_rxfh_context *ctx;
+
+	WARN_ONCE(!rtnl_is_locked() &&
+		  !lockdep_is_held_type(&dev->ethtool->rss_lock, -1),
+		  "RSS context lock assertion failed\n");
+
+	netdev_err(dev, "device error, RSS context %d lost\n", context_id);
+	ctx = xa_erase(&dev->ethtool->rss_ctx, context_id);
+	kfree(ctx);
+}
+EXPORT_SYMBOL(ethtool_rxfh_context_lost);
-- 
2.45.2