From nobody Sun Feb 8 11:22:06 2026 Received: from mail.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 52E1733F9; Tue, 20 Aug 2024 03:04:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=150.107.74.76 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724123045; cv=none; b=XtK1uORLP82tr3u/H5uWRqed3RN8P9tVIIHsWsRVviS3uRKCDcvMBYf41bu4hYGjHhUtsSWwgFw+6e9qcvkTPqSlPQXbL4Kk1B3hy2g/VHAokdHRr4+4TfUAFMdQwYcW2BM6VKtYV4VLvih02kFLfocDkZuSLgzFcbjt/C6dJAc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724123045; c=relaxed/simple; bh=OjjfPsRQw2C5OYfWFUNyPBR+zTrnb8hFbXcYKzQlOJ8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=dlMWEoJZntLyZN9aRyuGEGGOleKMMYp5VFc+yRrI9E2X38TIPstppF1qZsWal6xZd6VTm60EBswSSc394WcTz6RgQxRIOz68AxUFfHOwd4GZcXTw/z8yGyI2OVUj2ZMfazwwyP6NG3I7Bcey8VFvr0lp1GYmcyr69ACEducfSuY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au; spf=pass smtp.mailfrom=ellerman.id.au; dkim=pass (2048-bit key) header.d=ellerman.id.au header.i=@ellerman.id.au header.b=njMO9TNU; arc=none smtp.client-ip=150.107.74.76 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ellerman.id.au Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ellerman.id.au header.i=@ellerman.id.au header.b="njMO9TNU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1724123041; bh=zOJXN3PPcGbNvywa22BP3hA8HhqWXwzidaOciMyqTGg=; h=From:To:Cc:Subject:Date:From; b=njMO9TNUd8w07bVzEmCHfZBWYSHFjyDQ2Eh/HuPH3RNxwcPshGk1qDY4/FdJYJ2Di opc/M6BpX7Fjei0n1tUmLTA3yLAO2ChcYzonDX0byT6ostYCB+HDhBISTj+k13mcG0 CIRNXv7/9MXxKMMJWUniI9jyX4zY2y48LannEJ0iYgO+IO6wnJzwXb0BJbOxf8bAEU 1EjJOAY/9m5ew2WmEKgWYw10/1DfygMN0UymGJUMmTzj9NSxaWpEVvKq3zwMh5VAoe 0JHKpadeR06QeaQ016L1Lton0Bx1AdktGOi1e1+nlXzYdwtLi9iExqJ4JP4D66QLsr qopox6JhliG1A== Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mail.ozlabs.org (Postfix) with ESMTPSA id 4WnvSK3h96z4w2F; Tue, 20 Aug 2024 13:04:01 +1000 (AEST) From: Michael Ellerman To: cassel@kernel.org Cc: dlemoal@kernel.org, linux-ide@vger.kernel.org, , , , linux-ppc@kolla.no, vidra@ufal.mff.cuni.cz Subject: [PATCH v2] ata: pata_macio: Fix DMA table overflow Date: Tue, 20 Aug 2024 13:03:58 +1000 Message-ID: <20240820030358.627711-1-mpe@ellerman.id.au> X-Mailer: git-send-email 2.46.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Kolbj=C3=B8rn and Jon=C3=A1=C5=A1 reported that their 32-bit PowerMacs were= crashing in pata-macio since commit 09fe2bfa6b83 ("ata: pata_macio: Fix max_segment_size with PAGE_SIZE =3D=3D 64K"). For example: kernel BUG at drivers/ata/pata_macio.c:544! Oops: Exception in kernel mode, sig: 5 [#1] BE PAGE_SIZE=3D4K MMU=3DHash SMP NR_CPUS=3D2 DEBUG_PAGEALLOC PowerMac ... NIP pata_macio_qc_prep+0xf4/0x190 LR pata_macio_qc_prep+0xfc/0x190 Call Trace: 0xc1421660 (unreliable) ata_qc_issue+0x14c/0x2d4 __ata_scsi_queuecmd+0x200/0x53c ata_scsi_queuecmd+0x50/0xe0 scsi_queue_rq+0x788/0xb1c __blk_mq_issue_directly+0x58/0xf4 blk_mq_plug_issue_direct+0x8c/0x1b4 blk_mq_flush_plug_list.part.0+0x584/0x5e0 __blk_flush_plug+0xf8/0x194 __submit_bio+0x1b8/0x2e0 submit_bio_noacct_nocheck+0x230/0x304 btrfs_work_helper+0x200/0x338 process_one_work+0x1a8/0x338 worker_thread+0x364/0x4c0 kthread+0x100/0x104 start_kernel_thread+0x10/0x14 That commit increased max_segment_size to 64KB, with the justification that the SCSI core was already using that size when PAGE_SIZE =3D=3D 64KB, and that there was existing logic to split over-sized requests. However with a sufficiently large request, the splitting logic causes each sg to be split into two commands in the DMA table, leading to overflow of the DMA table, triggering the BUG_ON(). With default settings the bug doesn't trigger, because the request size is limited by max_sectors_kb =3D=3D 1280, however max_sectors_kb can be increased, and apparently some distros do that by default using udev rules. Fix the bug for 4KB kernels by reverting to the old max_segment_size. For 64KB kernels the sg_tablesize needs to be halved, to allow for the possibility that each sg will be split into two. Fixes: 09fe2bfa6b83 ("ata: pata_macio: Fix max_segment_size with PAGE_SIZE = =3D=3D 64K") Cc: stable@vger.kernel.org # v6.10+ Reported-by: Kolbj=C3=B8rn Barmen Closes: https://lore.kernel.org/all/62d248bb-e97a-25d2-bcf2-9160c518cae5@ko= lla.no/ Reported-by: Jon=C3=A1=C5=A1 Vidra Closes: https://lore.kernel.org/all/3b6441b8-06e6-45da-9e55-f92f2c86933e@uf= al.mff.cuni.cz/ Tested-by: Kolbj=C3=B8rn Barmen Signed-off-by: Michael Ellerman --- drivers/ata/pata_macio.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) v2: Namespace the defines as requested by Damien. Tab align the defines. diff --git a/drivers/ata/pata_macio.c b/drivers/ata/pata_macio.c index 1b85e8bf4ef9..1cb8d24b088f 100644 --- a/drivers/ata/pata_macio.c +++ b/drivers/ata/pata_macio.c @@ -208,6 +208,19 @@ static const char* macio_ata_names[] =3D { /* Don't let a DMA segment go all the way to 64K */ #define MAX_DBDMA_SEG 0xff00 =20 +#ifdef CONFIG_PAGE_SIZE_64KB +/* + * The SCSI core requires the segment size to cover at least a page, so + * for 64K page size kernels it must be at least 64K. However the + * hardware can't handle 64K, so pata_macio_qc_prep() will split large + * requests. To handle the split requests the tablesize must be halved. + */ +#define PATA_MACIO_MAX_SEGMENT_SIZE SZ_64K +#define PATA_MACIO_SG_TABLESIZE (MAX_DCMDS / 2) +#else +#define PATA_MACIO_MAX_SEGMENT_SIZE MAX_DBDMA_SEG +#define PATA_MACIO_SG_TABLESIZE MAX_DCMDS +#endif =20 /* * Wait 1s for disk to answer on IDE bus after a hard reset @@ -912,16 +925,10 @@ static int pata_macio_do_resume(struct pata_macio_pri= v *priv) =20 static const struct scsi_host_template pata_macio_sht =3D { __ATA_BASE_SHT(DRV_NAME), - .sg_tablesize =3D MAX_DCMDS, + .sg_tablesize =3D PATA_MACIO_SG_TABLESIZE, /* We may not need that strict one */ .dma_boundary =3D ATA_DMA_BOUNDARY, - /* - * The SCSI core requires the segment size to cover at least a page, so - * for 64K page size kernels this must be at least 64K. However the - * hardware can't handle 64K, so pata_macio_qc_prep() will split large - * requests. - */ - .max_segment_size =3D SZ_64K, + .max_segment_size =3D PATA_MACIO_MAX_SEGMENT_SIZE, .device_configure =3D pata_macio_device_configure, .sdev_groups =3D ata_common_sdev_groups, .can_queue =3D ATA_DEF_QUEUE, --=20 2.46.0