linux-kernel - Re: [PATCH v7 04/15] swiotlb: Add restricted DMA pool initialization

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Message-ID: <CALiNf29jpi7=UKFPc7TK8wiNbq6TL=Uj-Mvmj9HRvOLnr-r_Ow@mail.gmail.com>
Date:   Thu, 20 May 2021 14:39:08 +0800
From:   Claire Chang <tientzu@...omium.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>, mpe@...erman.id.au,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
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Subject: Re: [PATCH v7 04/15] swiotlb: Add restricted DMA pool initialization

On Thu, May 20, 2021 at 2:54 AM Florian Fainelli <f.fainelli@...il.com> wrote:
>
>
>
> On 5/17/2021 11:42 PM, Claire Chang wrote:
> > Add the initialization function to create restricted DMA pools from
> > matching reserved-memory nodes.
> >
> > Signed-off-by: Claire Chang <tientzu@...omium.org>
> > ---
> >  include/linux/device.h  |  4 +++
> >  include/linux/swiotlb.h |  3 +-
> >  kernel/dma/swiotlb.c    | 76 +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 82 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/device.h b/include/linux/device.h
> > index 38a2071cf776..4987608ea4ff 100644
> > --- a/include/linux/device.h
> > +++ b/include/linux/device.h
> > @@ -416,6 +416,7 @@ struct dev_links_info {
> >   * @dma_pools:       Dma pools (if dma'ble device).
> >   * @dma_mem: Internal for coherent mem override.
> >   * @cma_area:        Contiguous memory area for dma allocations
> > + * @dma_io_tlb_mem: Internal for swiotlb io_tlb_mem override.
> >   * @archdata:        For arch-specific additions.
> >   * @of_node: Associated device tree node.
> >   * @fwnode:  Associated device node supplied by platform firmware.
> > @@ -521,6 +522,9 @@ struct device {
> >  #ifdef CONFIG_DMA_CMA
> >       struct cma *cma_area;           /* contiguous memory area for dma
> >                                          allocations */
> > +#endif
> > +#ifdef CONFIG_DMA_RESTRICTED_POOL
> > +     struct io_tlb_mem *dma_io_tlb_mem;
> >  #endif
> >       /* arch specific additions */
> >       struct dev_archdata     archdata;
> > diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> > index 216854a5e513..03ad6e3b4056 100644
> > --- a/include/linux/swiotlb.h
> > +++ b/include/linux/swiotlb.h
> > @@ -72,7 +72,8 @@ extern enum swiotlb_force swiotlb_force;
> >   *           range check to see if the memory was in fact allocated by this
> >   *           API.
> >   * @nslabs:  The number of IO TLB blocks (in groups of 64) between @start and
> > - *           @end. This is command line adjustable via setup_io_tlb_npages.
> > + *           @end. For default swiotlb, this is command line adjustable via
> > + *           setup_io_tlb_npages.
> >   * @used:    The number of used IO TLB block.
> >   * @list:    The free list describing the number of free entries available
> >   *           from each index.
> > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> > index b849b01a446f..1d8eb4de0d01 100644
> > --- a/kernel/dma/swiotlb.c
> > +++ b/kernel/dma/swiotlb.c
> > @@ -39,6 +39,13 @@
> >  #ifdef CONFIG_DEBUG_FS
> >  #include <linux/debugfs.h>
> >  #endif
> > +#ifdef CONFIG_DMA_RESTRICTED_POOL
> > +#include <linux/io.h>
> > +#include <linux/of.h>
> > +#include <linux/of_fdt.h>
> > +#include <linux/of_reserved_mem.h>
> > +#include <linux/slab.h>
> > +#endif
> >
> >  #include <asm/io.h>
> >  #include <asm/dma.h>
> > @@ -690,3 +697,72 @@ static int __init swiotlb_create_default_debugfs(void)
> >  late_initcall(swiotlb_create_default_debugfs);
> >
> >  #endif
> > +
> > +#ifdef CONFIG_DMA_RESTRICTED_POOL
> > +static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
> > +                                 struct device *dev)
> > +{
> > +     struct io_tlb_mem *mem = rmem->priv;
> > +     unsigned long nslabs = rmem->size >> IO_TLB_SHIFT;
> > +
> > +     if (dev->dma_io_tlb_mem)
> > +             return 0;
> > +
> > +     /*
> > +      * Since multiple devices can share the same pool, the private data,
> > +      * io_tlb_mem struct, will be initialized by the first device attached
> > +      * to it.
> > +      */
> > +     if (!mem) {
> > +             mem = kzalloc(struct_size(mem, slots, nslabs), GFP_KERNEL);
> > +             if (!mem)
> > +                     return -ENOMEM;
> > +
> > +             if (PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
> > +                     kfree(mem);
> > +                     return -EINVAL;
>
> This could probably deserve a warning here to indicate that the reserved
> area must be accessible within the linear mapping as I would expect a
> lot of people to trip over that.

Ok. Will add it.

>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> --
> Florian