linux-kernel - RE: [PATCH] RDMA/siw: work around clang stack size warning

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Message-ID:
 <BN8PR15MB2513B863DCE33BF222FA6D1B9978A@BN8PR15MB2513.namprd15.prod.outlook.com>
Date: Tue, 24 Jun 2025 10:47:25 +0000
From: Bernard Metzler <BMT@...ich.ibm.com>
To: Arnd Bergmann <arnd@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>,
        Leon
 Romanovsky <leon@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>
CC: Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers
	<nick.desaulniers+lkml@...il.com>,
        Bill Wendling <morbo@...gle.com>,
        Justin
 Stitt <justinstitt@...gle.com>,
        Potnuri Bharat Teja <bharat@...lsio.com>,
        Showrya M N <showrya@...lsio.com>, Eric Biggers <ebiggers@...gle.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>
Subject: RE:  [PATCH] RDMA/siw: work around clang stack size warning



> -----Original Message-----
> From: Arnd Bergmann <arnd@...nel.org>
> Sent: Friday, June 20, 2025 1:43 PM
> To: Bernard Metzler <BMT@...ich.ibm.com>; Jason Gunthorpe <jgg@...pe.ca>;
> Leon Romanovsky <leon@...nel.org>; Nathan Chancellor <nathan@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>; Nick Desaulniers
> <nick.desaulniers+lkml@...il.com>; Bill Wendling <morbo@...gle.com>; Justin
> Stitt <justinstitt@...gle.com>; Potnuri Bharat Teja <bharat@...lsio.com>;
> Showrya M N <showrya@...lsio.com>; Eric Biggers <ebiggers@...gle.com>;
> linux-rdma@...r.kernel.org; linux-kernel@...r.kernel.org;
> llvm@...ts.linux.dev
> Subject: [EXTERNAL] [PATCH] RDMA/siw: work around clang stack size warning
> 
> From: Arnd Bergmann <arnd@...db.de>
> 
> clang inlines a lot of functions into siw_qp_sq_process(), with the
> aggregate stack frame blowing the warning limit in some configurations:
> 
> drivers/infiniband/sw/siw/siw_qp_tx.c:1014:5: error: stack frame size
> (1544) exceeds limit (1280) in 'siw_qp_sq_process' [-Werror,-Wframe-larger-
> than]
> 
> The real problem here is the array of kvec structures in siw_tx_hdt that
> makes up the majority of the consumed stack space.
> 
> Ideally there would be a way to avoid allocating the array on the
> stack, but that would require a larger rework. Add a noinline_for_stack
> annotation to avoid the warning for now, and make clang behave the same
> way as gcc here. The combined stack usage is still similar, but is spread
> over multiple functions now.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/infiniband/sw/siw/siw_qp_tx.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c
> b/drivers/infiniband/sw/siw/siw_qp_tx.c
> index 6432bce7d083..3a08f57d2211 100644
> --- a/drivers/infiniband/sw/siw/siw_qp_tx.c
> +++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
> @@ -277,6 +277,15 @@ static int siw_qp_prepare_tx(struct siw_iwarp_tx
> *c_tx)
>  	return PKT_FRAGMENTED;
>  }
> 
> +static noinline_for_stack int
> +siw_sendmsg(struct socket *sock, unsigned int msg_flags,
> +	    struct kvec *vec, size_t num, size_t len)
> +{
> +	struct msghdr msg = { .msg_flags = msg_flags };
> +
> +	return kernel_sendmsg(sock, &msg, vec, num, len);
> +}
> +
>  /*
>   * Send out one complete control type FPDU, or header of FPDU carrying
>   * data. Used for fixed sized packets like Read.Requests or zero length
> @@ -285,12 +294,11 @@ static int siw_qp_prepare_tx(struct siw_iwarp_tx
> *c_tx)
>  static int siw_tx_ctrl(struct siw_iwarp_tx *c_tx, struct socket *s,
>  			      int flags)
>  {
> -	struct msghdr msg = { .msg_flags = flags };
>  	struct kvec iov = { .iov_base =
>  				    (char *)&c_tx->pkt.ctrl + c_tx->ctrl_sent,
>  			    .iov_len = c_tx->ctrl_len - c_tx->ctrl_sent };
> 
> -	int rv = kernel_sendmsg(s, &msg, &iov, 1, iov.iov_len);
> +	int rv = siw_sendmsg(s, flags, &iov, 1, iov.iov_len);
> 
>  	if (rv >= 0) {
>  		c_tx->ctrl_sent += rv;
> @@ -427,13 +435,13 @@ static void siw_unmap_pages(struct kvec *iov,
> unsigned long kmap_mask, int len)
>   * Write out iov referencing hdr, data and trailer of current FPDU.
>   * Update transmit state dependent on write return status
>   */
> -static int siw_tx_hdt(struct siw_iwarp_tx *c_tx, struct socket *s)
> +static noinline_for_stack int siw_tx_hdt(struct siw_iwarp_tx *c_tx,
> +					 struct socket *s)
>  {
>  	struct siw_wqe *wqe = &c_tx->wqe_active;
>  	struct siw_sge *sge = &wqe->sqe.sge[c_tx->sge_idx];
>  	struct kvec iov[MAX_ARRAY];
>  	struct page *page_array[MAX_ARRAY];
> -	struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_EOR };
> 
>  	int seg = 0, do_crc = c_tx->do_crc, is_kva = 0, rv;
>  	unsigned int data_len = c_tx->bytes_unsent, hdr_len = 0, trl_len = 0,
> @@ -586,14 +594,16 @@ static int siw_tx_hdt(struct siw_iwarp_tx *c_tx,
> struct socket *s)
>  		rv = siw_0copy_tx(s, page_array, &wqe->sqe.sge[c_tx->sge_idx],
>  				  c_tx->sge_off, data_len);
>  		if (rv == data_len) {
> -			rv = kernel_sendmsg(s, &msg, &iov[seg], 1, trl_len);
> +
> +			rv = siw_sendmsg(s, MSG_DONTWAIT | MSG_EOR, &iov[seg],
> +					 1, trl_len);
>  			if (rv > 0)
>  				rv += data_len;
>  			else
>  				rv = data_len;
>  		}
>  	} else {
> -		rv = kernel_sendmsg(s, &msg, iov, seg + 1,
> +		rv = siw_sendmsg(s, MSG_DONTWAIT | MSG_EOR, iov, seg + 1,
>  				    hdr_len + data_len + trl_len);
>  		siw_unmap_pages(iov, kmap_mask, seg);
>  	}
> --
> 2.39.5

looks good and was tested.

Acked-by: Bernard Metzler <bmt@...ich.ibm.com>