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Subject: Re: [PATCH 14/14] staging: android: ion: Add UNMAPPED heap type and
 helper
To:     "Andrew F. Davis" <afd@ti.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?Q?Arve_Hj=c3=b8nnev=c3=a5g?= <arve@android.com>
Cc:     devel@driverdev.osuosl.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
References: <20190111180523.27862-1-afd@ti.com>
 <20190111180523.27862-15-afd@ti.com>
 <bd3c15f2-2635-588e-80b4-18e8e44d27b3@redhat.com>
 <ee3bb691-8c9b-457c-5da3-522a4baff140@ti.com>
From:   Laura Abbott <labbott@redhat.com>
Message-ID: <5718cc6c-1082-fec8-5c97-3f52bcfd98d9@redhat.com>
Date:   Tue, 15 Jan 2019 10:43:51 -0800
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On 1/15/19 7:58 AM, Andrew F. Davis wrote:
> On 1/14/19 8:32 PM, Laura Abbott wrote:
>> On 1/11/19 10:05 AM, Andrew F. Davis wrote:
>>> The "unmapped" heap is very similar to the carveout heap except
>>> the backing memory is presumed to be unmappable by the host, in
>>> my specific case due to firewalls. This memory can still be
>>> allocated from and used by devices that do have access to the
>>> backing memory.
>>>
>>> Based originally on the secure/unmapped heap from Linaro for
>>> the OP-TEE SDP implementation, this was re-written to match
>>> the carveout heap helper code.
>>>
>>> Suggested-by: Etienne Carriere <etienne.carriere@linaro.org>
>>> Signed-off-by: Andrew F. Davis <afd@ti.com>
>>> ---
>>>    drivers/staging/android/ion/Kconfig           |  10 ++
>>>    drivers/staging/android/ion/Makefile          |   1 +
>>>    drivers/staging/android/ion/ion.h             |  16 +++
>>>    .../staging/android/ion/ion_unmapped_heap.c   | 123 ++++++++++++++++++
>>>    drivers/staging/android/uapi/ion.h            |   3 +
>>>    5 files changed, 153 insertions(+)
>>>    create mode 100644 drivers/staging/android/ion/ion_unmapped_heap.c
>>>
>>> diff --git a/drivers/staging/android/ion/Kconfig
>>> b/drivers/staging/android/ion/Kconfig
>>> index 0fdda6f62953..a117b8b91b14 100644
>>> --- a/drivers/staging/android/ion/Kconfig
>>> +++ b/drivers/staging/android/ion/Kconfig
>>> @@ -42,3 +42,13 @@ config ION_CMA_HEAP
>>>          Choose this option to enable CMA heaps with Ion. This heap is
>>> backed
>>>          by the Contiguous Memory Allocator (CMA). If your system has
>>> these
>>>          regions, you should say Y here.
>>> +
>>> +config ION_UNMAPPED_HEAP
>>> +    bool "ION unmapped heap support"
>>> +    depends on ION
>>> +    help
>>> +      Choose this option to enable UNMAPPED heaps with Ion. This heap is
>>> +      backed in specific memory pools, carveout from the Linux memory.
>>> +      Unlike carveout heaps these are assumed to be not mappable by
>>> +      kernel or user-space.
>>> +      Unless you know your system has these regions, you should say N
>>> here.
>>> diff --git a/drivers/staging/android/ion/Makefile
>>> b/drivers/staging/android/ion/Makefile
>>> index 17f3a7569e3d..c71a1f3de581 100644
>>> --- a/drivers/staging/android/ion/Makefile
>>> +++ b/drivers/staging/android/ion/Makefile
>>> @@ -4,3 +4,4 @@ obj-$(CONFIG_ION_SYSTEM_HEAP) += ion_system_heap.o
>>> ion_page_pool.o
>>>    obj-$(CONFIG_ION_CARVEOUT_HEAP) += ion_carveout_heap.o
>>>    obj-$(CONFIG_ION_CHUNK_HEAP) += ion_chunk_heap.o
>>>    obj-$(CONFIG_ION_CMA_HEAP) += ion_cma_heap.o
>>> +obj-$(CONFIG_ION_UNMAPPED_HEAP) += ion_unmapped_heap.o
>>> diff --git a/drivers/staging/android/ion/ion.h
>>> b/drivers/staging/android/ion/ion.h
>>> index 97b2876b165a..ce74332018ba 100644
>>> --- a/drivers/staging/android/ion/ion.h
>>> +++ b/drivers/staging/android/ion/ion.h
>>> @@ -341,4 +341,20 @@ static inline struct ion_heap
>>> *ion_chunk_heap_create(phys_addr_t base, size_t si
>>>    }
>>>    #endif
>>>    +#ifdef CONFIG_ION_UNMAPPED_HEAP
>>> +/**
>>> + * ion_unmapped_heap_create
>>> + * @base:        base address of carveout memory
>>> + * @size:        size of carveout memory region
>>> + *
>>> + * Creates an unmapped ion_heap using the passed in data
>>> + */
>>> +struct ion_heap *ion_unmapped_heap_create(phys_addr_t base, size_t
>>> size);
>>> +#else
>>> +struct ion_heap *ion_unmapped_heap_create(phys_addr_t base, size_t size)
>>> +{
>>> +    return ERR_PTR(-ENODEV);
>>> +}
>>> +#endif
>>> +
>>>    #endif /* _ION_H */
>>> diff --git a/drivers/staging/android/ion/ion_unmapped_heap.c
>>> b/drivers/staging/android/ion/ion_unmapped_heap.c
>>> new file mode 100644
>>> index 000000000000..7602b659c2ec
>>> --- /dev/null
>>> +++ b/drivers/staging/android/ion/ion_unmapped_heap.c
>>> @@ -0,0 +1,123 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * ION Memory Allocator unmapped heap helper
>>> + *
>>> + * Copyright (C) 2015-2016 Texas Instruments Incorporated -
>>> http://www.ti.com/
>>> + *    Andrew F. Davis <afd@ti.com>
>>> + *
>>> + * ION "unmapped" heaps are physical memory heaps not by default
>>> mapped into
>>> + * a virtual address space. The buffer owner can explicitly request
>>> kernel
>>> + * space mappings but the underlying memory may still not be
>>> accessible for
>>> + * various reasons, such as firewalls.
>>> + */
>>> +
>>> +#include <linux/err.h>
>>> +#include <linux/genalloc.h>
>>> +#include <linux/scatterlist.h>
>>> +#include <linux/slab.h>
>>> +
>>> +#include "ion.h"
>>> +
>>> +#define ION_UNMAPPED_ALLOCATE_FAIL -1
>>> +
>>> +struct ion_unmapped_heap {
>>> +    struct ion_heap heap;
>>> +    struct gen_pool *pool;
>>> +};
>>> +
>>> +static phys_addr_t ion_unmapped_allocate(struct ion_heap *heap,
>>> +                     unsigned long size)
>>> +{
>>> +    struct ion_unmapped_heap *unmapped_heap =
>>> +        container_of(heap, struct ion_unmapped_heap, heap);
>>> +    unsigned long offset;
>>> +
>>> +    offset = gen_pool_alloc(unmapped_heap->pool, size);
>>> +    if (!offset)
>>> +        return ION_UNMAPPED_ALLOCATE_FAIL;
>>> +
>>> +    return offset;
>>> +}
>>> +
>>> +static void ion_unmapped_free(struct ion_heap *heap, phys_addr_t addr,
>>> +                  unsigned long size)
>>> +{
>>> +    struct ion_unmapped_heap *unmapped_heap =
>>> +        container_of(heap, struct ion_unmapped_heap, heap);
>>> +
>>> +    gen_pool_free(unmapped_heap->pool, addr, size);
>>> +}
>>> +
>>> +static int ion_unmapped_heap_allocate(struct ion_heap *heap,
>>> +                      struct ion_buffer *buffer,
>>> +                      unsigned long size,
>>> +                      unsigned long flags)
>>> +{
>>> +    struct sg_table *table;
>>> +    phys_addr_t paddr;
>>> +    int ret;
>>> +
>>> +    table = kmalloc(sizeof(*table), GFP_KERNEL);
>>> +    if (!table)
>>> +        return -ENOMEM;
>>> +    ret = sg_alloc_table(table, 1, GFP_KERNEL);
>>> +    if (ret)
>>> +        goto err_free;
>>> +
>>> +    paddr = ion_unmapped_allocate(heap, size);
>>> +    if (paddr == ION_UNMAPPED_ALLOCATE_FAIL) {
>>> +        ret = -ENOMEM;
>>> +        goto err_free_table;
>>> +    }
>>> +
>>> +    sg_set_page(table->sgl, pfn_to_page(PFN_DOWN(paddr)), size, 0);
>>> +    buffer->sg_table = table;
>>> +
>>
>>
>> If this memory is actually unmapped this is not going to work because
>> the struct page will not be valid.
>>
> 
> If it will never get mapped then it doesn't need a valid struct page as
> far as I can tell. We only use it as a marker to where the start of
> backing memory is, and that is calculated based on the struct page
> pointer address, not its contents.
> 

You can't rely on pfn_to_page returning a valid page pointer if the
pfn doesn't point to reserved memory. Even if you aren't relying
on the contents, that's no guarantee you can use that to to get
the valid pfn back. You can get away with that sometimes but it's
not correct to rely on it all the time.

>>> +    return 0;
>>> +
>>> +err_free_table:
>>> +    sg_free_table(table);
>>> +err_free:
>>> +    kfree(table);
>>> +    return ret;
>>> +}
>>> +
>>> +static void ion_unmapped_heap_free(struct ion_buffer *buffer)
>>> +{
>>> +    struct ion_heap *heap = buffer->heap;
>>> +    struct sg_table *table = buffer->sg_table;
>>> +    struct page *page = sg_page(table->sgl);
>>> +    phys_addr_t paddr = PFN_PHYS(page_to_pfn(page));
>>> +
>>> +    ion_unmapped_free(heap, paddr, buffer->size);
>>> +    sg_free_table(buffer->sg_table);
>>> +    kfree(buffer->sg_table);
>>> +}
>>> +
>>> +static struct ion_heap_ops unmapped_heap_ops = {
>>> +    .allocate = ion_unmapped_heap_allocate,
>>> +    .free = ion_unmapped_heap_free,
>>> +    /* no .map_user, user mapping of unmapped heaps not allowed */
>>> +    .map_kernel = ion_heap_map_kernel,
>>> +    .unmap_kernel = ion_heap_unmap_kernel,
>>> +};
>>> +
>>> +struct ion_heap *ion_unmapped_heap_create(phys_addr_t base, size_t size)
>>> +{
>>> +    struct ion_unmapped_heap *unmapped_heap;
>>> +
>>> +    unmapped_heap = kzalloc(sizeof(*unmapped_heap), GFP_KERNEL);
>>> +    if (!unmapped_heap)
>>> +        return ERR_PTR(-ENOMEM);
>>> +
>>> +    unmapped_heap->pool = gen_pool_create(PAGE_SHIFT, -1);
>>> +    if (!unmapped_heap->pool) {
>>> +        kfree(unmapped_heap);
>>> +        return ERR_PTR(-ENOMEM);
>>> +    }
>>> +    gen_pool_add(unmapped_heap->pool, base, size, -1);
>>> +    unmapped_heap->heap.ops = &unmapped_heap_ops;
>>> +    unmapped_heap->heap.type = ION_HEAP_TYPE_UNMAPPED;
>>> +
>>> +    return &unmapped_heap->heap;
>>> +}
>>> diff --git a/drivers/staging/android/uapi/ion.h
>>> b/drivers/staging/android/uapi/ion.h
>>> index 5d7009884c13..d5f98bc5f340 100644
>>> --- a/drivers/staging/android/uapi/ion.h
>>> +++ b/drivers/staging/android/uapi/ion.h
>>> @@ -19,6 +19,8 @@
>>>     *                 carveout heap, allocations are physically
>>>     *                 contiguous
>>>     * @ION_HEAP_TYPE_DMA:         memory allocated via DMA API
>>> + * @ION_HEAP_TYPE_UNMAPPED:     memory not intended to be mapped into
>>> the
>>> + *                 linux address space unless for debug cases
>>>     * @ION_NUM_HEAPS:         helper for iterating over heaps, a bit mask
>>>     *                 is used to identify the heaps, so only 32
>>>     *                 total heap types are supported
>>> @@ -29,6 +31,7 @@ enum ion_heap_type {
>>>        ION_HEAP_TYPE_CARVEOUT,
>>>        ION_HEAP_TYPE_CHUNK,
>>>        ION_HEAP_TYPE_DMA,
>>> +    ION_HEAP_TYPE_UNMAPPED,
>>>        ION_HEAP_TYPE_CUSTOM, /*
>>>                       * must be last so device specific heaps always
>>>                       * are at the end of this enum
>>>
>>
>> Overall this seems way too similar to the carveout heap
>> to justify adding another heap type. It also still missing
>> the part of where exactly you call ion_unmapped_heap_create.
>> Figuring that out is one of the blocking items for moving
>> Ion out of staging.
>>
> 
> I agree with this being almost a 1:1 copy of the carveout heap, I'm just
> not sure of a good way to do this without a new heap type. Adding flags
> to the existing carveout type seem a bit messy. Plus then those flags
> should be valid for other heap types, gets complicated quickly..
> 
> I'll reply to the second part in your other top level response.
> 
> Andrew
> 
>> Thanks,
>> Laura