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

Claire Chang
2021-05-20T06:39:37Z

On Thu, May 20, 2021 at 2:54 AM Florian Fainelli <f.fainelli@gmail.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@chromium.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@gmail.com>
> --
> Florian