On Tue, Apr 01, 2014 at 10:51:58AM +0900, Jungseok Lee wrote:
> This patch corrects kernel command line handler when io_tlb_nslabs
> is set to 0.
>
> A current implementation allocates default size memory (64MB) when
> 0 is given to io_tlb_nslabs ("swiotlb=0") by kernel command line.
> In other words, memory is allocated unintentionally.
What are the other IOMMUs that end up taking over the DMA ops?
Or do you end up with no DMA ops?
>
> Signed-off-by: Jungseok Lee <jays.lee@xxxxxxxxxxx>
> Signed-off-by: Sungjinn Chung <sungjinn.chung@xxxxxxxxxxx>
> ---
> lib/swiotlb.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index b604b83..9fe9f71 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -55,6 +55,8 @@
>
> int swiotlb_force;
>
> +static int swiotlb_no_use;
> +
> /*
> * 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
> @@ -102,6 +104,8 @@ setup_io_tlb_npages(char *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);
> + if (!io_tlb_nslabs)
> + swiotlb_no_use = 1;
> }
> if (*str == ',')
> ++str;
> @@ -212,7 +216,7 @@ swiotlb_init(int verbose)
> unsigned char *vstart;
> unsigned long bytes;
>
> - if (!io_tlb_nslabs) {
> + if (!swiotlb_no_use && !io_tlb_nslabs) {
> io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
> io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
> }
> @@ -244,7 +248,7 @@ swiotlb_late_init_with_default_size(size_t default_size)
> unsigned int order;
> int rc = 0;
>
> - if (!io_tlb_nslabs) {
> + if (!swiotlb_no_use && !io_tlb_nslabs) {
> io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
> io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
> }
> --
> 1.7.10.4
>
>
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