linux-kernel - Re: [PATCH v6 23/27] x86: Don't panic if can not alloc buffer for swiotlb

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Message-ID: <20121222022113.GD3468@phenom.dumpdata.com>
Date:	Fri, 21 Dec 2012 21:21:13 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...ne.org>
Subject: Re: [PATCH v6 23/27] x86: Don't panic if can not alloc buffer for
 swiotlb

On Thu, Dec 13, 2012 at 02:02:17PM -0800, Yinghai Lu wrote:
> Normal boot path on system with iommu support:
> swiotlb buffer will be allocated early at first and then try to initialize
> iommu, if iommu for intel or amd could setup properly, swiotlb buffer
> will be freed.
> 
> The early allocating is with bootmem, and could panic when we try to use
> kdump with buffer above 4G only.
> 
> Replace the panic with WARN, and the kernel can go on without swiotlb,
> and could iommu later.


What if SWIOTLB is the only option? Meaning there are no other IOMMUs?


> 
> Signed-off-by: Yinghai Lu <yinghai@...ne.org>
> ---
>  arch/x86/kernel/pci-swiotlb.c |    5 ++++-
>  include/linux/swiotlb.h       |    2 +-
>  lib/swiotlb.c                 |   17 +++++++++++------
>  3 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
> index 6c483ba..6f93eb7 100644
> --- a/arch/x86/kernel/pci-swiotlb.c
> +++ b/arch/x86/kernel/pci-swiotlb.c
> @@ -91,7 +91,10 @@ IOMMU_INIT(pci_swiotlb_detect_4gb,
>  void __init pci_swiotlb_init(void)
>  {
>  	if (swiotlb) {
> -		swiotlb_init(0);
> +		if (swiotlb_init(0)) {
> +			swiotlb = 0;
> +			return;
> +		}
>  		dma_ops = &swiotlb_dma_ops;
>  	}
>  }
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index 8d08b3e..f7535d1 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -22,7 +22,7 @@ extern int swiotlb_force;
>   */
>  #define IO_TLB_SHIFT 11
>  
> -extern void swiotlb_init(int verbose);
> +int swiotlb_init(int verbose);
>  extern void swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
>  extern unsigned long swiotlb_nr_tbl(void);
>  extern int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs);
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index f114bf6..6b99ea7 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -170,7 +170,7 @@ void __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
>   * Statically reserve bounce buffer space and initialize bounce buffer data
>   * structures for the software IO TLB used to implement the DMA API.
>   */
> -static void __init
> +static int __init
>  swiotlb_init_with_default_size(size_t default_size, int verbose)
>  {
>  	unsigned long bytes;
> @@ -185,17 +185,22 @@ swiotlb_init_with_default_size(size_t default_size, int verbose)
>  	/*
>  	 * Get IO TLB memory from the low pages
>  	 */
> -	io_tlb_start = alloc_bootmem_low_pages(PAGE_ALIGN(bytes));
> -	if (!io_tlb_start)
> -		panic("Cannot allocate SWIOTLB buffer");
> +	io_tlb_start = alloc_bootmem_low_pages_nopanic(PAGE_ALIGN(bytes));
> +	if (!io_tlb_start) {
> +		WARN(1, "Cannot allocate SWIOTLB buffer");
> +		return -1;
> +	}
>  
>  	swiotlb_init_with_tbl(io_tlb_start, io_tlb_nslabs, verbose);
> +
> +	return 0;
>  }
>  
> -void __init
> +int __init
>  swiotlb_init(int verbose)
>  {
> -	swiotlb_init_with_default_size(64 * (1<<20), verbose);	/* default to 64MB */
> +	/* default to 64MB */
> +	return swiotlb_init_with_default_size(64 * (1<<20), verbose);
>  }
>  
>  /*
> -- 
> 1.7.10.4
> 
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