linux-kernel - [PATCH rdma-next] RDMA/bng_re: Remove prefetch instruction

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Message-ID: <20251126-remove-prefetch-v1-1-fcac22007ea7@nvidia.com>
Date: Wed, 26 Nov 2025 09:57:37 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Siva Reddy Kallam <siva.kallam@...adcom.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Leon Romanovsky <leon@...nel.org>,
	Usman Ansari <usman.ansari@...adcom.com>
Cc: linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	kernel test robot <lkp@...el.com>
Subject: [PATCH rdma-next] RDMA/bng_re: Remove prefetch instruction

From: Leon Romanovsky <leonro@...dia.com>

The prefetch instruction is meant to speed up access to memory referenced
by its address argument. In the bng_re code path, it has no effect,
because the pointer refers to a function that is executed immediately
afterward.

The issue was identified due to the following kbuild compilation error:

  drivers/infiniband/hw/bng_re/bng_fw.c: In function 'bng_re_creq_irq':
    drivers/infiniband/hw/bng_re/bng_fw.c:278:9: error: implicit
    declaration of function 'prefetch' [-Wimplicit-function-declaration]
      278 |     prefetch(bng_re_get_qe(hwq, sw_cons, NULL));
          |     ^~~~~~~~

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202511260607.Kuxn4NnN-lkp@intel.com/
Fixes: 4f830cd8d7fe ("RDMA/bng_re: Add infrastructure for enabling Firmware channel")
Signed-off-by: Leon Romanovsky <leonro@...dia.com>
---
 drivers/infiniband/hw/bng_re/bng_fw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/bng_re/bng_fw.c b/drivers/infiniband/hw/bng_re/bng_fw.c
index 803610fb9c58..7d9539113cf5 100644
--- a/drivers/infiniband/hw/bng_re/bng_fw.c
+++ b/drivers/infiniband/hw/bng_re/bng_fw.c
@@ -525,7 +525,7 @@ static irqreturn_t bng_re_creq_irq(int irq, void *dev_instance)
 	hwq = &creq->hwq;
 	/* Prefetch the CREQ element */
 	sw_cons = HWQ_CMP(hwq->cons, hwq);
-	prefetch(bng_re_get_qe(hwq, sw_cons, NULL));
+	bng_re_get_qe(hwq, sw_cons, NULL);
 
 	tasklet_schedule(&creq->creq_tasklet);
 	return IRQ_HANDLED;

---
base-commit: 01dad9ca37c60d08f71e2ef639875ae895deede6
change-id: 20251126-remove-prefetch-ac5cba4dc9ca

Best regards,
--  
Leon Romanovsky <leonro@...dia.com>