linux-kernel - Re: [PATCH v1 4/4] swiotlb: panic if nslabs is too small

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Date:   Fri, 19 Aug 2022 19:20:31 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     dongli.zhang@...cle.com
Cc:     ak@...ux.intel.com, akpm@...ux-foundation.org,
        alexander.sverdlin@...ia.com, andi.kleen@...el.com, bp@...en8.de,
        bp@...e.de, cminyard@...sta.com, corbet@....net,
        damien.lemoal@...nsource.wdc.com, dave.hansen@...ux.intel.com,
        hch@...radead.org, iommu@...ts.linux-foundation.org,
        joe.jin@...cle.com, joe@...ches.com, keescook@...omium.org,
        kirill.shutemov@...el.com, kys@...rosoft.com,
        linux-doc@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        ltykernel@...il.com, michael.h.kelley@...rosoft.com,
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        vkuznets@...hat.com, wei.liu@...nel.org, x86@...nel.org
Subject: Re: [PATCH v1 4/4] swiotlb: panic if nslabs is too small

> Panic on purpose if nslabs is too small, in order to sync with the remap
> retry logic.
> 
> In addition, print the number of bytes for tlb alloc failure.
> 
> Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
> ---
>  kernel/dma/swiotlb.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index fd21f4162f4b..1758b724c7a8 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -242,6 +242,9 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
>  	if (swiotlb_force_disable)
>  		return;
>  
> +	if (nslabs < IO_TLB_MIN_SLABS)
> +		panic("%s: nslabs = %lu too small\n", __func__, nslabs);

Hi,

This patch breaks MIPS. Please take a look. Thanks.

On v5.19.0:
  Linux version 5.19.0 (builder@...ldhost) (mips64-openwrt-linux-musl-gcc (OpenWrt GCC 11.2.0 r19590-042d558536) 11.2.0, GNU ld (GNU Binutils) 2.37) #0 SMP Sun Jul 31 15:12:47 2022
  Skipping L2 locking due to reduced L2 cache size
  CVMSEG size: 0 cache lines (0 bytes)
  printk: bootconsole [early0] enabled
  CPU0 revision is: 000d9301 (Cavium Octeon II)
  Kernel sections are not in the memory maps
  Wasting 278528 bytes for tracking 4352 unused pages
  Initrd not found or empty - disabling initrd
  Using appended Device Tree.
  software IO TLB: SWIOTLB bounce buffer size adjusted to 0MB
  software IO TLB: mapped [mem 0x0000000004b0c000-0x0000000004b4c000] (0MB)

On v6.0-rc1, with
  commit 0bf28fc40d89 ("swiotlb: panic if nslabs is too small")
  commit 20347fca71a3 ("swiotlb: split up the global swiotlb lock")
  commit 534ea58b3ceb ("Revert "MIPS: octeon: Remove vestiges of CONFIG_CAVIUM_RESERVE32"")

  Linux version 6.0.0-rc1 (builder@...ldhost) (mips64-openwrt-linux-musl-gcc (OpenWrt GCC 11.2.0 r19590-042d558536) 11.2.0, GNU ld (GNU Binutils) 2.37) #0 SMP Sun Jul 31 15:12:47 2022
  Failed to allocate CAVIUM_RESERVE32 memory area
  Skipping L2 locking due to reduced L2 cache size
  CVMSEG size: 0 cache lines (0 bytes)
  printk: bootconsole [early0] enabled
  CPU0 revision is: 000d9301 (Cavium Octeon II)
  Kernel sections are not in the memory maps
  Wasting 278528 bytes for tracking 4352 unused pages
  Initrd not found or empty - disabling initrd
  Using appended Device Tree.
  software IO TLB: SWIOTLB bounce buffer size adjusted to 0MB
  software IO TLB: area num 1.
  Kernel panic - not syncing: swiotlb_init_remap: nslabs = 128 too small

On v6.0-rc1, with
  commit 20347fca71a3 ("swiotlb: split up the global swiotlb lock")
  commit 534ea58b3ceb ("Revert "MIPS: octeon: Remove vestiges of CONFIG_CAVIUM_RESERVE32"")

  Linux version 6.0.0-rc1+ (builder@...ldhost) (mips64-openwrt-linux-musl-gcc (OpenWrt GCC 11.2.0 r19590-042d558536) 11.2.0, GNU ld (GNU Binutils) 2.37) #0 SMP Sun Jul 31 15:12:47 2022
  Failed to allocate CAVIUM_RESERVE32 memory area
  Skipping L2 locking due to reduced L2 cache size
  CVMSEG size: 0 cache lines (0 bytes)
  printk: bootconsole [early0] enabled
  CPU0 revision is: 000d9301 (Cavium Octeon II)
  Kernel sections are not in the memory maps
  Wasting 278528 bytes for tracking 4352 unused pages
  Initrd not found or empty - disabling initrd
  Using appended Device Tree.
  software IO TLB: SWIOTLB bounce buffer size adjusted to 0MB
  software IO TLB: area num 1.
  software IO TLB: mapped [mem 0x0000000004c0c000-0x0000000004c4c000] (0MB)