Re: [PATCH net-next V6] net/mlx5: Improve write-combining test reliability for ARM64 Grace CPUs

[Paolo Abeni <pabeni@redhat.com>]

Hi,

On 9/28/25 11:08 PM, Tariq Toukan wrote:
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/wc.c b/drivers/net/ethernet/mellanox/mlx5/core/wc.c
> index 999d6216648a..c281153bd411 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/wc.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/wc.c
> @@ -7,6 +7,10 @@
>  #include "mlx5_core.h"
>  #include "wq.h"
>  
> +#if IS_ENABLED(CONFIG_KERNEL_MODE_NEON) && IS_ENABLED(CONFIG_ARM64)
> +#include <asm/neon.h>
> +#endif
> +
>  #define TEST_WC_NUM_WQES 255
>  #define TEST_WC_LOG_CQ_SZ (order_base_2(TEST_WC_NUM_WQES))
>  #define TEST_WC_SQ_LOG_WQ_SZ TEST_WC_LOG_CQ_SZ
> @@ -255,6 +259,27 @@ static void mlx5_wc_destroy_sq(struct mlx5_wc_sq *sq)
>  	mlx5_wq_destroy(&sq->wq_ctrl);
>  }
>  
> +static void mlx5_iowrite64_copy(struct mlx5_wc_sq *sq, __be32 mmio_wqe[16],
> +				size_t mmio_wqe_size, unsigned int offset)
> +{
> +#if IS_ENABLED(CONFIG_KERNEL_MODE_NEON) && IS_ENABLED(CONFIG_ARM64)
> +	if (cpu_has_neon()) {
> +		kernel_neon_begin();
> +		asm volatile
> +		(".arch_extension simd;\n\t"

Here I'm observing build errors with aarch64-linux-gnu-gcc 12.1.1
20220507 (Red Hat Cross 12.1.1-1):

/tmp/cchqHdeI.s: Assembler messages:
/tmp/cchqHdeI.s:746: Error: unknown architectural extension `simd;'

I can't reproduce the error on any recent compiler version via
godbolt.org, so I *think* this should not block/be reverted for the MR,
but could you please have a look soonish?

Thanks,

Paolo