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Subject: Re: [PATCH 14/14] staging: android: ion: Add UNMAPPED heap type and
 helper
To:     Laura Abbott <labbott@redhat.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>
 <5718cc6c-1082-fec8-5c97-3f52bcfd98d9@redhat.com>
 <59d7f837-acb7-8ee0-ef47-f38f0c798d26@redhat.com>
From:   "Andrew F. Davis" <afd@ti.com>
Message-ID: <615d2b04-e5d3-e074-6794-590a560b7282@ti.com>
Date:   Wed, 16 Jan 2019 10:18:57 -0600
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On 1/15/19 1:11 PM, Laura Abbott wrote:
> On 1/15/19 10:43 AM, Laura Abbott wrote:
>> 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.
>>
> 
> I found https://lore.kernel.org/lkml/20190111181731.11782-1-hch@lst.de/T/#u
> which I think is closer to what we might want to be looking at.
> 

That does seem to be something that could be used, I'll have to try to
understand this for a bit how to bring that into use here.

>>>>> +    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
>>
>