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Thu, 21 May 2026 02:45:26 -0700 (PDT) Received: from [192.168.88.32] ([169.155.232.242]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49033d9eca8sm52423715e9.12.2026.05.21.02.45.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 May 2026 02:45:26 -0700 (PDT) Message-ID: Date: Thu, 21 May 2026 11:45:25 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next] net: ibm: emac: Clear MAL descriptors without memset To: Rosen Penev , netdev@vger.kernel.org Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , open list References: <20260517033621.1839397-1-rosenp@gmail.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260517033621.1839397-1-rosenp@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/17/26 5:36 AM, Rosen Penev wrote: > Clear MAL descriptor rings with explicit field stores instead of > memset(). The descriptor rings are carved from MAL coherent DMA memory, > which may be mapped uncached on 32-bit powerpc. The optimized memset() > path can use dcbz there and trigger an alignment warning. > > The skb tracking arrays remain ordinary CPU memory and still use memset(). > > Assisted-by: Codex:GPT-5.5 > Signed-off-by: Rosen Penev > --- > drivers/net/ethernet/ibm/emac/core.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c > index 1fd7cb50c568..7ab5c944f5de 100644 > --- a/drivers/net/ethernet/ibm/emac/core.c > +++ b/drivers/net/ethernet/ibm/emac/core.c > @@ -1161,6 +1161,17 @@ static void emac_clean_rx_ring(struct emac_instance *dev) > } > } > > +static void emac_clear_mal_desc(struct mal_descriptor *desc, int count) > +{ > + int i; > + > + for (i = 0; i < count; i++) { > + desc[i].ctrl = 0; > + desc[i].data_len = 0; > + desc[i].data_ptr = 0; Sashiko noted that the compiler could still optimize the above to a memset(). Perhaps a barrier() is needed here? /P