linux-kernel - Re: [PATCH net v2 3/3] net: bcmgenet: synchronize UMAC

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Message-ID: <07b4cb83-08db-449d-9d73-88e84fa570bd@broadcom.com>
Date: Fri, 26 Apr 2024 11:19:43 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Doug Berger <opendmb@...il.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH net v2 3/3] net: bcmgenet: synchronize UMAC_CMD access

On 4/25/24 15:27, Doug Berger wrote:
> The UMAC_CMD register is written from different execution
> contexts and has insufficient synchronization protections to
> prevent possible corruption. Of particular concern are the
> acceses from the phy_device delayed work context used by the
> adjust_link call and the BH context that may be used by the
> ndo_set_rx_mode call.
> 
> A spinlock is added to the driver to protect contended register
> accesses (i.e. reg_lock) and it is used to synchronize accesses
> to UMAC_CMD.
> 
> Fixes: 1c1008c793fa ("net: bcmgenet: add main driver file")
> Cc: stable@...r.kernel.org
> Signed-off-by: Doug Berger <opendmb@...il.com>

Acked-by: Florian Fainelli <florian.fainelli@...adcom.com>

As a bug fix this is totally fine. I believe there could be an 
improvement made in 'net-next' whereby we introduce an 
unimac_rmw_locked() or something that essentially does:

void unimac_rmw_locked(struct bcmgenet_priv *priv, u32 offset, u32 
mask_clear, u32 mask_set)
{
	u32 reg;
	spin_lock_bh(&priv->reg_lock);
	reg = bcmgenet_umac_readl(priv, offset);
	reg &= ~mask_clear;
	reg |= mask_set;
	bcmgenet_umac_writel(priv, reg, offset);
	spin_unlock_bh(&priv->reg_lock);
}

At least a couple of callers could benefit from it. Thanks!
-- 
Florian

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