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Re: [PATCH] modify the IO_TLB_SEGSIZE to io_tlb_segsize configurable as

To: xiaomin1 <xiaoming.wang@intel.com>
Subject: Re: [PATCH] modify the IO_TLB_SEGSIZE to io_tlb_segsize configurable as flexible requirement about SW-IOMMU.
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Thu, 5 Feb 2015 14:32:41 -0500
Cc: ralf@linux-mips.org, boris.ostrovsky@oracle.com, david.vrabel@citrix.com, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, akpm@linux-foundation.org, linux@horizon.com, lauraa@codeaurora.org, heiko.carstens@de.ibm.com, d.kasatkin@samsung.com, takahiro.akashi@linaro.org, chris@chris-wilson.co.uk, pebolle@tiscali.nl, Chuansheng Liu <chuansheng.liu@intel.com>, Zhang Dongxing <dongxing.zhang@intel.com>
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On Fri, Feb 06, 2015 at 07:01:14AM +0800, xiaomin1 wrote:
> The maximum of SW-IOMMU is limited to 2^11*128 = 256K.
> While in different platform and different requirements this seems improper.
> So modify the IO_TLB_SEGSIZE to io_tlb_segsize as configurable is make sense.

More details please. What is the issue you are hitting?

> 
> Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
> Signed-off-by: Zhang Dongxing <dongxing.zhang@intel.com>
> Signed-off-by: xiaomin1 <xiaoming.wang@intel.com>
> ---
>  arch/mips/cavium-octeon/dma-octeon.c |    2 +-
>  arch/mips/netlogic/common/nlm-dma.c  |    2 +-
>  drivers/xen/swiotlb-xen.c            |    6 +++---
>  include/linux/swiotlb.h              |    8 +------
>  lib/swiotlb.c                        |   39 
> ++++++++++++++++++++++++----------
>  5 files changed, 34 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/mips/cavium-octeon/dma-octeon.c 
> b/arch/mips/cavium-octeon/dma-octeon.c
> index 3778655..a521af6 100644
> --- a/arch/mips/cavium-octeon/dma-octeon.c
> +++ b/arch/mips/cavium-octeon/dma-octeon.c
> @@ -312,7 +312,7 @@ void __init plat_swiotlb_setup(void)
>               swiotlbsize = 64 * (1<<20);
>  #endif
>       swiotlb_nslabs = swiotlbsize >> IO_TLB_SHIFT;
> -     swiotlb_nslabs = ALIGN(swiotlb_nslabs, IO_TLB_SEGSIZE);
> +     swiotlb_nslabs = ALIGN(swiotlb_nslabs, io_tlb_segsize);
>       swiotlbsize = swiotlb_nslabs << IO_TLB_SHIFT;
>  
>       octeon_swiotlb = alloc_bootmem_low_pages(swiotlbsize);
> diff --git a/arch/mips/netlogic/common/nlm-dma.c 
> b/arch/mips/netlogic/common/nlm-dma.c
> index f3d4ae8..eeffa8f 100644
> --- a/arch/mips/netlogic/common/nlm-dma.c
> +++ b/arch/mips/netlogic/common/nlm-dma.c
> @@ -99,7 +99,7 @@ void __init plat_swiotlb_setup(void)
>  
>       swiotlbsize = 1 << 20; /* 1 MB for now */
>       swiotlb_nslabs = swiotlbsize >> IO_TLB_SHIFT;
> -     swiotlb_nslabs = ALIGN(swiotlb_nslabs, IO_TLB_SEGSIZE);
> +     swiotlb_nslabs = ALIGN(swiotlb_nslabs, io_tlb_segsize);
>       swiotlbsize = swiotlb_nslabs << IO_TLB_SHIFT;
>  
>       nlm_swiotlb = alloc_bootmem_low_pages(swiotlbsize);
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 810ad41..3b3e9fe 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -164,11 +164,11 @@ xen_swiotlb_fixup(void *buf, size_t size, unsigned long 
> nslabs)
>       dma_addr_t dma_handle;
>       phys_addr_t p = virt_to_phys(buf);
>  
> -     dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
> +     dma_bits = get_order(io_tlb_segsize << IO_TLB_SHIFT) + PAGE_SHIFT;
>  
>       i = 0;
>       do {
> -             int slabs = min(nslabs - i, (unsigned long)IO_TLB_SEGSIZE);
> +             int slabs = min(nslabs - i, (unsigned long)io_tlb_segsize);
>  
>               do {
>                       rc = xen_create_contiguous_region(
> @@ -187,7 +187,7 @@ static unsigned long xen_set_nslabs(unsigned long nr_tbl)
>  {
>       if (!nr_tbl) {
>               xen_io_tlb_nslabs = (64 * 1024 * 1024 >> IO_TLB_SHIFT);
> -             xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE);
> +             xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, io_tlb_segsize);
>       } else
>               xen_io_tlb_nslabs = nr_tbl;
>  
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index e7a018e..13506db 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -8,13 +8,7 @@ struct dma_attrs;
>  struct scatterlist;
>  
>  extern int swiotlb_force;
> -
> -/*
> - * Maximum allowable number of contiguous slabs to map,
> - * must be a power of 2.  What is the appropriate value ?
> - * The complexity of {map,unmap}_single is linearly dependent on this value.
> - */
> -#define IO_TLB_SEGSIZE       128
> +extern int io_tlb_segsize;
>  
>  /*
>   * log of the size of each IO TLB slab.  The number of slabs is command line
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index 4abda07..50c415a 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -56,6 +56,15 @@
>  int swiotlb_force;
>  
>  /*
> + * Maximum allowable number of contiguous slabs to map,
> + * must be a power of 2.  What is the appropriate value ?
> + * define io_tlb_segsize as a parameter
> + * which can be changed dynamically in config file for special usage.
> + * The complexity of {map,unmap}_single is linearly dependent on this value.
> + */
> +int io_tlb_segsize = 128;
> +
> +/*
>   * Used to do a quick range check in swiotlb_tbl_unmap_single and
>   * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by 
> this
>   * API.
> @@ -97,12 +106,20 @@ static DEFINE_SPINLOCK(io_tlb_lock);
>  static int late_alloc;
>  
>  static int __init
> +setup_io_tlb_segsize(char *str)
> +{
> +     get_option(&str, &io_tlb_segsize);
> +     return 0;
> +}
> +__setup("io_tlb_segsize=", setup_io_tlb_segsize);
> +
> +static int __init
>  setup_io_tlb_npages(char *str)
>  {
>       if (isdigit(*str)) {
>               io_tlb_nslabs = simple_strtoul(str, &str, 0);
> -             /* avoid tail segment of size < IO_TLB_SEGSIZE */
> -             io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
> +             /* avoid tail segment of size < io_tlb_segsize */
> +             io_tlb_nslabs = ALIGN(io_tlb_nslabs, io_tlb_segsize);
>       }
>       if (*str == ',')
>               ++str;
> @@ -183,7 +200,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long 
> nslabs, int verbose)
>  
>       /*
>        * Allocate and initialize the free list array.  This array is used
> -      * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE
> +      * to find contiguous free memory regions of size up to io_tlb_segsize
>        * between io_tlb_start and io_tlb_end.
>        */
>       io_tlb_list = memblock_virt_alloc(
> @@ -193,7 +210,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long 
> nslabs, int verbose)
>                               PAGE_ALIGN(io_tlb_nslabs * sizeof(phys_addr_t)),
>                               PAGE_SIZE);
>       for (i = 0; i < io_tlb_nslabs; i++) {
> -             io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
> +             io_tlb_list[i] = io_tlb_segsize - OFFSET(i, io_tlb_segsize);
>               io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
>       }
>       io_tlb_index = 0;
> @@ -217,7 +234,7 @@ swiotlb_init(int verbose)
>  
>       if (!io_tlb_nslabs) {
>               io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
> -             io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
> +             io_tlb_nslabs = ALIGN(io_tlb_nslabs, io_tlb_segsize);
>       }
>  
>       bytes = io_tlb_nslabs << IO_TLB_SHIFT;
> @@ -249,7 +266,7 @@ swiotlb_late_init_with_default_size(size_t default_size)
>  
>       if (!io_tlb_nslabs) {
>               io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
> -             io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
> +             io_tlb_nslabs = ALIGN(io_tlb_nslabs, io_tlb_segsize);
>       }
>  
>       /*
> @@ -308,7 +325,7 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long 
> nslabs)
>  
>       /*
>        * Allocate and initialize the free list array.  This array is used
> -      * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE
> +      * to find contiguous free memory regions of size up to io_tlb_segsize
>        * between io_tlb_start and io_tlb_end.
>        */
>       io_tlb_list = (unsigned int *)__get_free_pages(GFP_KERNEL,
> @@ -324,7 +341,7 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long 
> nslabs)
>               goto cleanup4;
>  
>       for (i = 0; i < io_tlb_nslabs; i++) {
> -             io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
> +             io_tlb_list[i] = io_tlb_segsize - OFFSET(i, io_tlb_segsize);
>               io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
>       }
>       io_tlb_index = 0;
> @@ -493,7 +510,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
>  
>                       for (i = index; i < (int) (index + nslots); i++)
>                               io_tlb_list[i] = 0;
> -                     for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != 
> IO_TLB_SEGSIZE - 1) && io_tlb_list[i]; i--)
> +                     for (i = index - 1; (OFFSET(i, io_tlb_segsize) != 
> io_tlb_segsize - 1) && io_tlb_list[i]; i--)
>                               io_tlb_list[i] = ++count;
>                       tlb_addr = io_tlb_start + (index << IO_TLB_SHIFT);
>  
> @@ -571,7 +588,7 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, 
> phys_addr_t tlb_addr,
>        */
>       spin_lock_irqsave(&io_tlb_lock, flags);
>       {
> -             count = ((index + nslots) < ALIGN(index + 1, IO_TLB_SEGSIZE) ?
> +             count = ((index + nslots) < ALIGN(index + 1, io_tlb_segsize) ?
>                        io_tlb_list[index + nslots] : 0);
>               /*
>                * Step 1: return the slots to the free list, merging the
> @@ -585,7 +602,7 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, 
> phys_addr_t tlb_addr,
>                * Step 2: merge the returned slots with the preceding slots,
>                * if available (non zero)
>                */
> -             for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != 
> IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
> +             for (i = index - 1; (OFFSET(i, io_tlb_segsize) != 
> io_tlb_segsize -1) && io_tlb_list[i]; i--)
>                       io_tlb_list[i] = ++count;
>       }
>       spin_unlock_irqrestore(&io_tlb_lock, flags);
> -- 
> 1.7.9.5
> 

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