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SubjectRe: [PATCH v6 24/27] x86: Add swiotlb force off support
On Thu, Dec 13, 2012 at 02:02:18PM -0800, Yinghai Lu wrote:
> So use could disable swiotlb from command line, even swiotlb support
> is compiled in. Just like we have intel_iommu=on and intel_iommu=off.

Does this have any usage besides testing?

And also pls in the future use scripts/get_maintainer.pl so
that you can extract from the email of the maintainer (which would be me).

>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> ---
> Documentation/kernel-parameters.txt | 7 +++++++
> arch/x86/kernel/pci-swiotlb.c | 10 +++++-----
> drivers/iommu/amd_iommu.c | 1 +
> include/linux/swiotlb.h | 1 +
> lib/swiotlb.c | 5 ++++-
> 5 files changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 20e248c..08b4c9d 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2832,6 +2832,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>
> swiotlb= [IA-64] Number of I/O TLB slabs
>
> + swiotlb=[force|off|on] [KNL] disable or enable swiotlb.
> + force
> + on
> + Enable swiotlb.
> + off
> + Disable swiotlb.
> +
> switches= [HW,M68k]
>
> sysfs.deprecated=0|1 [KNL]
> diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
> index 6f93eb7..80afd3b 100644
> --- a/arch/x86/kernel/pci-swiotlb.c
> +++ b/arch/x86/kernel/pci-swiotlb.c
> @@ -58,12 +58,12 @@ static struct dma_map_ops swiotlb_dma_ops = {
> */
> int __init pci_swiotlb_detect_override(void)
> {
> - int use_swiotlb = swiotlb | swiotlb_force;
> -
> if (swiotlb_force)
> swiotlb = 1;
> + else if (swiotlb_force_off)
> + swiotlb = 0;
>
> - return use_swiotlb;
> + return swiotlb;
> }
> IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
> pci_xen_swiotlb_detect,
> @@ -76,9 +76,9 @@ IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
> */
> int __init pci_swiotlb_detect_4gb(void)
> {
> - /* don't initialize swiotlb if iommu=off (no_iommu=1) */
> + /* don't initialize swiotlb if iommu=off (no_iommu=1) or force off */
> #ifdef CONFIG_X86_64
> - if (!no_iommu && max_pfn > MAX_DMA32_PFN)
> + if (!no_iommu && !swiotlb_force_off && max_pfn > MAX_DMA32_PFN)
> swiotlb = 1;
> #endif
> return swiotlb;
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 55074cb..4f370d3 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -3082,6 +3082,7 @@ int __init amd_iommu_init_dma_ops(void)
> unhandled = device_dma_ops_init();
> if (unhandled && max_pfn > MAX_DMA32_PFN) {
> /* There are unhandled devices - initialize swiotlb for them */
> + WARN(swiotlb_force_off, "Please remove swiotlb=off\n");
> swiotlb = 1;
> }
>
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index f7535d1..dd7cf65 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -8,6 +8,7 @@ struct dma_attrs;
> struct scatterlist;
>
> extern int swiotlb_force;
> +extern int swiotlb_force_off;
>
> /*
> * Maximum allowable number of contiguous slabs to map,
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index 6b99ea7..3f51b2c 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -51,6 +51,7 @@
> #define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
>
> int swiotlb_force;
> +int swiotlb_force_off;
>
> /*
> * Used to do a quick range check in swiotlb_tbl_unmap_single and
> @@ -102,8 +103,10 @@ setup_io_tlb_npages(char *str)
> }
> if (*str == ',')
> ++str;
> - if (!strcmp(str, "force"))
> + if (!strcmp(str, "force") || !strcmp(str, "on"))
> swiotlb_force = 1;
> + if (!strcmp(str, "off"))
> + swiotlb_force_off = 1;
>
> return 1;
> }
> --
> 1.7.10.4
>
> --
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