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Tue, 20 Oct 2026 10:27:07 -0700 (PDT) Received: from localhost ([2a03:2880:7ff:4::]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ad802917c3sm487593a91.7.2026.10.20.10.27.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Oct 2026 10:27:07 -0700 (PDT) From: Dimitri Daskalakis To: "David S. Miller" Cc: Alexander Duyck , Jakub Kicinski , kernel-team@meta.com, Andrew Lunn , Eric Dumazet , Paolo Abeni , Simon Horman , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Mohsin Bashir , Bobby Eshleman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Dimitri Daskalakis , Dimitri Daskalakis Subject: [PATCH net] eth: fbnic: Correct packet header prefetch Date: Tue, 20 Oct 2026 10:27:06 -0700 Message-ID: <20261020172706.1090951-1-dimitri.daskalakis1@gmail.com> X-Mailer: git-send-email 2.52.0 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Dimitri Daskalakis The existing call to net_prefetch() fetched a stale address. The data pointer is not initialized until after the call to xdp_prepare_buff(). Thus, making the prefetch ineffective. Open code the address calcuation to give the prefetch as much time as possible. This was found by manual code inspection. No issues have been observed from this. Fixes: 9064ab485f04 ("eth: fbnic: Prefetch packet headers on Rx") Signed-off-by: Jakub Kicinski Signed-off-by: Dimitri Daskalakis --- drivers/net/ethernet/meta/fbnic/fbnic_txrx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c b/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c index 10caacffee0f..69cd96a4508f 100644 --- a/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c +++ b/drivers/net/ethernet/meta/fbnic/fbnic_txrx.c @@ -1011,7 +1011,7 @@ static void fbnic_pkt_prepare(struct fbnic_napi_vector *nv, u64 rcd, /* Build frame around buffer */ hdr_start = page_address(page) + hdr_pg_start; - net_prefetch(pkt->buff.data); + net_prefetch(hdr_start + headroom); xdp_prepare_buff(&pkt->buff, hdr_start, headroom, len - FBNIC_RX_PAD, true); -- 2.52.0