netdev - Re: [PATCH net v1 1/1] ethtool: fix clearing of WoL flags

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Date: Thu, 19 Oct 2023 12:50:48 +0200
From: Michal Kubecek <mkubecek@...e.cz>
To: Köry Maincent <kory.maincent@...tlin.com>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Lunn <andrew@...n.ch>, Eric Dumazet <edumazet@...gle.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Vladimir Oltean <olteanv@...il.com>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net v1 1/1] ethtool: fix clearing of WoL flags

On Thu, Oct 19, 2023 at 12:21:14PM +0200, Köry Maincent wrote:
> On Thu, 19 Oct 2023 11:51:40 +0200 > Michal Kubecek <mkubecek@...e.cz> wrote:
> > 
> > The issue was indeed introduced by commit 108a36d07c01 ("ethtool: Fix
> > mod state of verbose no_mask bitset"). The problem is that a "no mask"
> > verbose bitset only contains bit attributes for bits to be set. This
> > worked correctly before this commit because we were always updating
> > a zero bitmap (since commit 6699170376ab ("ethtool: fix application of
> > verbose no_mask bitset"), that is) so that the rest was left zero
> > naturally. But now the 1->0 change (old_val is true, bit not present in
> > netlink nest) no longer works.
> 
> Doh I had not seen this issue! Thanks you for reporting it.
> I will send the revert then and will update the fix for next merge-window.

Something like the diff below (against current mainline) might do the
trick but it's just an idea, not even build tested.

Michal


diff --git a/net/ethtool/bitset.c b/net/ethtool/bitset.c
index 883ed9be81f9..4d4398879c95 100644
--- a/net/ethtool/bitset.c
+++ b/net/ethtool/bitset.c
@@ -74,6 +74,28 @@ static void ethnl_bitmap32_clear(u32 *dst, unsigned int start, unsigned int end,
 	}
 }
 
+/**
+  * ethnl_bitmap32_equal() - Compare two bitmaps
+  * @map1:  first bitmap
+  * @map2:  second bitmap
+  * @nbits: bit size to compare
+  *
+  * Return: true if first @nbits are equal, false if not
+  */
+
+static bool ethnl_bitmap32_equal(const u32 *map1, const u32 *map2,
+				 unsigned int nbits)
+{
+	bool ret;
+
+	if (memcmp(map1, map2, nbits / 32 * sizeof(u32)))
+		return false;
+	if (nbits % 32 == 0)
+		return true;
+	return !((map1[nbits / 32] ^ map2[nbits / 32]) &
+		 ethnl_lower_bits(nbits % 32));
+}
+
 /**
  * ethnl_bitmap32_not_zero() - Check if any bit is set in an interval
  * @map:   bitmap to test
@@ -431,7 +453,7 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 			      ethnl_string_array_t names,
 			      struct netlink_ext_ack *extack, bool *mod)
 {
-	u32 *orig_bitmap, *saved_bitmap = NULL;
+	u32 *saved_bitmap = NULL;
 	struct nlattr *bit_attr;
 	bool no_mask;
 	bool dummy;
@@ -462,9 +484,6 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 			return -ENOMEM;
 		memcpy(saved_bitmap, bitmap, nbytes);
 		ethnl_bitmap32_clear(bitmap, 0, nbits, &dummy);
-		orig_bitmap = saved_bitmap;
-	} else {
-		orig_bitmap = bitmap;
 	}
 
 	nla_for_each_nested(bit_attr, tb[ETHTOOL_A_BITSET_BITS], rem) {
@@ -481,7 +500,7 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 				      names, extack);
 		if (ret < 0)
 			goto out;
-		old_val = orig_bitmap[idx / 32] & ((u32)1 << (idx % 32));
+		old_val = bitmap[idx / 32] & ((u32)1 << (idx % 32));
 		if (new_val != old_val) {
 			if (new_val)
 				bitmap[idx / 32] |= ((u32)1 << (idx % 32));
@@ -490,6 +509,8 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 			*mod = true;
 		}
 	}
+	if (saved_bitmap)
+		*mod = ethnl_bitmap32_cmp(saved_bitmap, bitmap, nbits);
 
 	ret = 0;
 out:

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