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From: Steven Price <steven.price@arm.com>
To: Claire Chang <tientzu@chromium.org>,
	Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	boris.ostrovsky@oracle.com, jgross@suse.com,
	Christoph Hellwig <hch@lst.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>
Cc: benh@kernel.crashing.org, paulus@samba.org,
	"list@263.net:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
	sstabellini@kernel.org, Robin Murphy <robin.murphy@arm.com>,
	grant.likely@arm.com, xypron.glpk@gmx.de,
	Thierry Reding <treding@nvidia.com>,
	mingo@kernel.org, bauerman@linux.ibm.com, peterz@infradead.org,
	Greg KH <gregkh@linuxfoundation.org>,
	Saravana Kannan <saravanak@google.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	heikki.krogerus@linux.intel.com,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	linux-devicetree <devicetree@vger.kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	linuxppc-dev@lists.ozlabs.org, xen-devel@lists.xenproject.org,
	Nicolas Boichat <drinkcat@chromium.org>,
	Jim Quinlan <james.quinlan@broadcom.com>,
	tfiga@chromium.org, bskeggs@redhat.com, bhelgaas@google.com,
	chris@chris-wilson.co.uk, daniel@ffwll.ch, airlied@linux.ie,
	dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	jani.nikula@linux.intel.com, jxgao@google.com,
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	maarten.lankhorst@linux.intel.com, matthew.auld@intel.com,
	nouveau@lists.freedesktop.org, rodrigo.vivi@intel.com,
	thomas.hellstrom@linux.intel.com
Subject: Re: [PATCH v5 05/16] swiotlb: Add restricted DMA pool initialization
Date: Fri, 23 Apr 2021 12:34:31 +0100	[thread overview]
Message-ID: <c9abca62-328d-d0d6-a8a6-a67475171f92@arm.com> (raw)
In-Reply-To: <20210422081508.3942748-6-tientzu@chromium.org>

On 22/04/2021 09:14, 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    | 80 +++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 86 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 57a9adb920bf..ffbb8724e06c 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>
> @@ -681,3 +688,76 @@ 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;
> +#ifdef CONFIG_ARM
> +		if (!PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
> +			kfree(mem);
> +			return -EINVAL;
> +		}
> +#endif /* CONFIG_ARM */
> +		swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, false);
> +
> +		rmem->priv = mem;
> +	}
> +
> +#ifdef CONFIG_DEBUG_FS
> +	if (!io_tlb_default_mem->debugfs)
> +		io_tlb_default_mem->debugfs =
> +			debugfs_create_dir("swiotlb", NULL);

At this point it's possible for io_tlb_default_mem to be NULL, leading 
to a splat.

But even then if it's not and we have the situation where debugfs==NULL 
then the debugfs_create_dir() here will cause a subsequent attempt in 
swiotlb_create_debugfs() to fail (directory already exists) leading to 
mem->debugfs being assigned an error value. I suspect the creation of 
the debugfs directory needs to be separated from io_tlb_default_mem 
being set.

Other than that I gave this series a go with our prototype of Arm's 
Confidential Computer Architecture[1] - since the majority of the 
guest's memory is protected from the host the restricted DMA pool allows 
(only) a small area to be shared with the host.

After fixing (well hacking round) the above it all seems to be working 
fine with virtio drivers.

Thanks,

Steve

[1] 
https://www.arm.com/why-arm/architecture/security-features/arm-confidential-compute-architecture

  reply	other threads:[~2021-04-23 11:34 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-22  8:14 [PATCH v5 00/16] Restricted DMA Claire Chang
2021-04-22  8:14 ` [PATCH v5 01/16] swiotlb: Fix the type of index Claire Chang
2021-04-23  7:11   ` Christoph Hellwig
2021-04-22  8:14 ` [PATCH v5 02/16] swiotlb: Refactor swiotlb init functions Claire Chang
2021-04-22  8:14 ` [PATCH v5 03/16] swiotlb: Refactor swiotlb_create_debugfs Claire Chang
2021-04-22  8:14 ` [PATCH v5 04/16] swiotlb: Add DMA_RESTRICTED_POOL Claire Chang
2021-04-22  8:14 ` [PATCH v5 05/16] swiotlb: Add restricted DMA pool initialization Claire Chang
2021-04-23 11:34   ` Steven Price [this message]
2021-04-26 16:37     ` Claire Chang
2021-04-28  9:50       ` Steven Price
2021-04-22  8:14 ` [PATCH v5 06/16] swiotlb: Add a new get_io_tlb_mem getter Claire Chang
2021-04-22  8:14 ` [PATCH v5 07/16] swiotlb: Update is_swiotlb_buffer to add a struct device argument Claire Chang
2021-04-22  8:15 ` [PATCH v5 08/16] swiotlb: Update is_swiotlb_active " Claire Chang
2021-04-23 13:31   ` Robin Murphy
2021-04-26 16:37     ` Claire Chang
2021-04-22  8:15 ` [PATCH v5 09/16] swiotlb: Bounce data from/to restricted DMA pool if available Claire Chang
2021-04-22  8:15 ` [PATCH v5 10/16] swiotlb: Move alloc_size to find_slots Claire Chang
2021-04-22  8:15 ` [PATCH v5 11/16] swiotlb: Refactor swiotlb_tbl_unmap_single Claire Chang
2021-04-22  8:15 ` [PATCH v5 12/16] dma-direct: Add a new wrapper __dma_direct_free_pages() Claire Chang
2021-04-22  8:15 ` [PATCH v5 13/16] swiotlb: Add restricted DMA alloc/free support Claire Chang
2021-04-22  8:15 ` [PATCH v5 14/16] dma-direct: Allocate memory from restricted DMA pool if available Claire Chang
2021-04-23 13:46   ` Robin Murphy
2021-05-03 14:26     ` Claire Chang
2021-04-22  8:15 ` [PATCH v5 15/16] dt-bindings: of: Add restricted DMA pool Claire Chang
2021-04-22  8:15 ` [PATCH v5 16/16] of: Add plumbing for " Claire Chang
2021-04-23  2:52   ` Claire Chang
2021-04-23 13:35   ` Robin Murphy
2021-04-26 16:38     ` Claire Chang
2021-05-10  9:53 ` [PATCH v5 00/16] Restricted DMA Claire Chang

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