linux-kernel - Re: [PATCH net v1] net: stmmac: TSO: Fix unbalanced DMA map/unmap for non-paged SKB data

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Message-ID: <20241205173431.0000779e@gmail.com>
Date: Thu, 5 Dec 2024 17:34:31 +0800
From: Furong Xu <0x1207@...il.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Jon Hunter <jonathanh@...dia.com>, Thierry Reding
 <thierry.reding@...il.com>, Robin Murphy <robin.murphy@....com>, Jakub
 Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu
 <joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Maxime
 Coquelin <mcoquelin.stm32@...il.com>, xfr@...look.com, Suraj Jaiswal
 <quic_jsuraj@...cinc.com>, Thierry Reding <treding@...dia.com>,
 "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>, Will Deacon
 <will@...nel.org>
Subject: Re: [PATCH net v1] net: stmmac: TSO: Fix unbalanced DMA map/unmap
 for non-paged SKB data

Hi Russell,

On Wed, 4 Dec 2024 17:45:43 +0000, "Russell King (Oracle)" <linux@...linux.org.uk> wrote:
> So yes, "des" is being offset, which will upset the unmap operation.
> Please try the following patch, thanks:
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 9b262cdad60b..c81ea8cdfe6e 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4192,8 +4192,8 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
>  	struct stmmac_txq_stats *txq_stats;
>  	struct stmmac_tx_queue *tx_q;
>  	u32 pay_len, mss, queue;
> +	dma_addr_t tso_des, des;
>  	u8 proto_hdr_len, hdr;
> -	dma_addr_t des;
>  	bool set_ic;
>  	int i;
>  
> @@ -4289,14 +4289,15 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
>  
>  		/* If needed take extra descriptors to fill the remaining payload */
>  		tmp_pay_len = pay_len - TSO_MAX_BUFF_SIZE;
> +		tso_des = des;
>  	} else {
>  		stmmac_set_desc_addr(priv, first, des);
>  		tmp_pay_len = pay_len;
> -		des += proto_hdr_len;
> +		tso_des = des + proto_hdr_len;
>  		pay_len = 0;
>  	}
>  
> -	stmmac_tso_allocator(priv, des, tmp_pay_len, (nfrags == 0), queue);
> +	stmmac_tso_allocator(priv, tso_des, tmp_pay_len, (nfrags == 0), queue);
>  
>  	/* In case two or more DMA transmit descriptors are allocated for this
>  	 * non-paged SKB data, the DMA buffer address should be saved to
> 

Much appreciated for your comments and suggestions, I sent a new patch to fix
this issue. Please let me know if you have any new advice.
https://lore.kernel.org/netdev/20241205091830.3719609-1-0x1207@gmail.com/

Thanks,
Furong