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Date:   Thu, 9 Nov 2017 09:36:02 +0800
From:   "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
To:     Robin Murphy <robin.murphy@....com>
CC:     Leon Romanovsky <leon@...nel.org>, <shaobo.xu@...el.com>,
        <xavier.huwei@....com>, <lijun_nudt@....com>, <oulijun@...wei.com>,
        <linux-rdma@...r.kernel.org>, <charles.chenxin@...wei.com>,
        <linuxarm@...wei.com>, <iommu@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <dledford@...hat.com>, <liuyixian@...wei.com>,
        <zhangxiping3@...wei.com>, <shaoboxu@....com>
Subject: Re: [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08



On 2017/11/1 20:26, Robin Murphy wrote:
> On 01/11/17 07:46, Wei Hu (Xavier) wrote:
>>
>> On 2017/10/12 20:59, Robin Murphy wrote:
>>> On 12/10/17 13:31, Wei Hu (Xavier) wrote:
>>>> On 2017/10/1 0:10, Leon Romanovsky wrote:
>>>>> On Sat, Sep 30, 2017 at 05:28:59PM +0800, Wei Hu (Xavier) wrote:
>>>>>> If the IOMMU is enabled, the length of sg obtained from
>>>>>> __iommu_map_sg_attrs is not 4kB. When the IOVA is set with the sg
>>>>>> dma address, the IOVA will not be page continuous. and the VA
>>>>>> returned from dma_alloc_coherent is a vmalloc address. However,
>>>>>> the VA obtained by the page_address is a discontinuous VA. Under
>>>>>> these circumstances, the IOVA should be calculated based on the
>>>>>> sg length, and record the VA returned from dma_alloc_coherent
>>>>>> in the struct of hem.
>>>>>>
>>>>>> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@...wei.com>
>>>>>> Signed-off-by: Shaobo Xu <xushaobo2@...wei.com>
>>>>>> Signed-off-by: Lijun Ou <oulijun@...wei.com>
>>>>>> ---
>>>>> Doug,
>>>>>
>>>>> I didn't invest time in reviewing it, but having "is_vmalloc_addr" in
>>>>> driver code to deal with dma_alloc_coherent is most probably wrong.
>>>>>
>>>>> Thanks
>>>> Hi,  Leon & Doug
>>>>     We refered the function named __ttm_dma_alloc_page in the kernel
>>>> code as below:
>>>>     And there are similar methods in bch_bio_map and mem_to_page
>>>> functions in current 4.14-rcx.
>>>>
>>>>         static struct dma_page *__ttm_dma_alloc_page(struct dma_pool *pool)
>>>>         {
>>>>             struct dma_page *d_page;
>>>>
>>>>             d_page = kmalloc(sizeof(struct dma_page), GFP_KERNEL);
>>>>             if (!d_page)
>>>>                 return NULL;
>>>>
>>>>             d_page->vaddr = dma_alloc_coherent(pool->dev, pool->size,
>>>>                                &d_page->dma,
>>>>                                    pool->gfp_flags);
>>>>             if (d_page->vaddr) {
>>>>                 if (is_vmalloc_addr(d_page->vaddr))
>>>>                     d_page->p = vmalloc_to_page(d_page->vaddr);
>>>>                 else
>>>>                     d_page->p = virt_to_page(d_page->vaddr);
>>> There are cases on various architectures where neither of those is
>>> right. Whether those actually intersect with TTM or RDMA use-cases is
>>> another matter, of course.
>>>
>>> What definitely is a problem is if you ever take that page and end up
>>> accessing it through any virtual address other than the one explicitly
>>> returned by dma_alloc_coherent(). That can blow the coherency wide open
>>> and invite data loss, right up to killing the whole system with a
>>> machine check on certain architectures.
>>>
>>> Robin.
>> Hi, Robin
>>     Thanks for your comment.
>>
>>     We have one problem and the related code as below.
>>     1. call dma_alloc_coherent function  serval times to alloc memory.
>>     2. vmap the allocated memory pages.
>>     3. software access memory by using the return virt addr of vmap
>>         and hardware using the dma addr of dma_alloc_coherent.
> The simple answer is "don't do that". Seriously. dma_alloc_coherent()
> gives you a CPU virtual address and a DMA address with which to access
> your buffer, and that is the limit of what you may infer about it. You
> have no guarantee that the virtual address is either in the linear map
> or vmalloc, and not some other special place. You have no guarantee that
> the underlying memory even has an associated struct page at all.
>
>>     When IOMMU is disabled in ARM64 architecture, we use virt_to_page()
>>     before vmap(), it works. And when IOMMU is enabled using
>>     virt_to_page() will cause calltrace later, we found the return
>>     addr of dma_alloc_coherent is vmalloc addr, so we add the
>>     condition judgement statement as below, it works. 
>>         for (i = 0; i < buf->nbufs; ++i)
>>                 pages[i] =
>>                     is_vmalloc_addr(buf->page_list[i].buf) ?
>>                     vmalloc_to_page(buf->page_list[i].buf) :
>>                     virt_to_page(buf->page_list[i].buf);
>>     Can you give us suggestion? better method?
> Oh my goodness, having now taken a closer look at this driver, I'm lost
> for words in disbelief. To pick just one example:
>
> 	u32 bits_per_long = BITS_PER_LONG;
> 	...
> 	if (bits_per_long == 64) {
> 		/* memory mapping nonsense */
> 	}
>
> WTF does the size of a long have to do with DMA buffer management!?
>
> Of course I can guess that it might be trying to make some tortuous
> inference about vmalloc space being constrained on 32-bit platforms, but
> still...
We will fix it. Thanks
>>     The related code as below:
>>         buf->page_list = kcalloc(buf->nbufs, sizeof(*buf->page_list),
>>                      GFP_KERNEL);
>>         if (!buf->page_list)
>>             return -ENOMEM;
>>
>>         for (i = 0; i < buf->nbufs; ++i) {
>>             buf->page_list[i].buf = dma_alloc_coherent(dev,
>>                                   page_size, &t,
>>                                   GFP_KERNEL);
>>             if (!buf->page_list[i].buf)
>>                 goto err_free;
>>
>>             buf->page_list[i].map = t;
>>             memset(buf->page_list[i].buf, 0, page_size);
>>         }
>>
>>         pages = kmalloc_array(buf->nbufs, sizeof(*pages),
>>                           GFP_KERNEL);
>>         if (!pages)
>>                 goto err_free;
>>
>>         for (i = 0; i < buf->nbufs; ++i)
>>                 pages[i] =
>>                     is_vmalloc_addr(buf->page_list[i].buf) ?
>>                     vmalloc_to_page(buf->page_list[i].buf) :
>>                     virt_to_page(buf->page_list[i].buf);
>>
>>         buf->direct.buf = vmap(pages, buf->nbufs, VM_MAP,
>>                            PAGE_KERNEL);
>>         kfree(pages);
>>         if (!buf->direct.buf)
>>                 goto err_free;
> OK, this is complete crap. As above, you cannot assume that a struct
> page even exists; even if it does you cannot assume that using a
> PAGE_KERNEL mapping will not result in mismatched attributes,
> unpredictable behaviour and data loss. Trying to remap coherent DMA
> allocations like this is just egregiously wrong.
>
> What I do like is that you can seemingly fix all this by simply deleting
> hns_roce_buf::direct and all the garbage code related to it, and using
> the page_list entries consistently because the alternate paths involving
> those appear to do the right thing already.
Hi, Robin
    Thanks for your suggestion.
    We will fix it.

    Regards
Wei Hu
> That is, of course, assuming that the buffers involved can be so large
> that it's not practical to just always make a single allocation and
> fragment it into multiple descriptors if the hardware does have some
> maximum length constraint - frankly I'm a little puzzled by the
> PAGE_SIZE * 2 threshold, given that that's not a fixed size.
>
> Robin.
>
>>     Regards
>> Wei Hu
>>>>             } else {
>>>>                 kfree(d_page);
>>>>                 d_page = NULL;
>>>>             }
>>>>             return d_page;
>>>>         }
>>>>
>>>>     Regards
>>>> Wei Hu
>>>>>>   drivers/infiniband/hw/hns/hns_roce_alloc.c |  5 ++++-
>>>>>>   drivers/infiniband/hw/hns/hns_roce_hem.c   | 30
>>>>>> +++++++++++++++++++++++++++---
>>>>>>   drivers/infiniband/hw/hns/hns_roce_hem.h   |  6 ++++++
>>>>>>   drivers/infiniband/hw/hns/hns_roce_hw_v2.c | 22 +++++++++++++++-------
>>>>>>   4 files changed, 52 insertions(+), 11 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_alloc.c
>>>>>> b/drivers/infiniband/hw/hns/hns_roce_alloc.c
>>>>>> index 3e4c525..a69cd4b 100644
>>>>>> --- a/drivers/infiniband/hw/hns/hns_roce_alloc.c
>>>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_alloc.c
>>>>>> @@ -243,7 +243,10 @@ int hns_roce_buf_alloc(struct hns_roce_dev
>>>>>> *hr_dev, u32 size, u32 max_direct,
>>>>>>                   goto err_free;
>>>>>>
>>>>>>               for (i = 0; i < buf->nbufs; ++i)
>>>>>> -                pages[i] = virt_to_page(buf->page_list[i].buf);
>>>>>> +                pages[i] =
>>>>>> +                    is_vmalloc_addr(buf->page_list[i].buf) ?
>>>>>> +                    vmalloc_to_page(buf->page_list[i].buf) :
>>>>>> +                    virt_to_page(buf->page_list[i].buf);
>>>>>>
>>>>>>               buf->direct.buf = vmap(pages, buf->nbufs, VM_MAP,
>>>>>>                              PAGE_KERNEL);
>>>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_hem.c
>>>>>> b/drivers/infiniband/hw/hns/hns_roce_hem.c
>>>>>> index 8388ae2..4a3d1d4 100644
>>>>>> --- a/drivers/infiniband/hw/hns/hns_roce_hem.c
>>>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_hem.c
>>>>>> @@ -200,6 +200,7 @@ static struct hns_roce_hem
>>>>>> *hns_roce_alloc_hem(struct hns_roce_dev *hr_dev,
>>>>>>                              gfp_t gfp_mask)
>>>>>>   {
>>>>>>       struct hns_roce_hem_chunk *chunk = NULL;
>>>>>> +    struct hns_roce_vmalloc *vmalloc;
>>>>>>       struct hns_roce_hem *hem;
>>>>>>       struct scatterlist *mem;
>>>>>>       int order;
>>>>>> @@ -227,6 +228,7 @@ static struct hns_roce_hem
>>>>>> *hns_roce_alloc_hem(struct hns_roce_dev *hr_dev,
>>>>>>               sg_init_table(chunk->mem, HNS_ROCE_HEM_CHUNK_LEN);
>>>>>>               chunk->npages = 0;
>>>>>>               chunk->nsg = 0;
>>>>>> +            memset(chunk->vmalloc, 0, sizeof(chunk->vmalloc));
>>>>>>               list_add_tail(&chunk->list, &hem->chunk_list);
>>>>>>           }
>>>>>>
>>>>>> @@ -243,7 +245,15 @@ static struct hns_roce_hem
>>>>>> *hns_roce_alloc_hem(struct hns_roce_dev *hr_dev,
>>>>>>           if (!buf)
>>>>>>               goto fail;
>>>>>>
>>>>>> -        sg_set_buf(mem, buf, PAGE_SIZE << order);
>>>>>> +        if (is_vmalloc_addr(buf)) {
>>>>>> +            vmalloc = &chunk->vmalloc[chunk->npages];
>>>>>> +            vmalloc->is_vmalloc_addr = true;
>>>>>> +            vmalloc->vmalloc_addr = buf;
>>>>>> +            sg_set_page(mem, vmalloc_to_page(buf),
>>>>>> +                    PAGE_SIZE << order, offset_in_page(buf));
>>>>>> +        } else {
>>>>>> +            sg_set_buf(mem, buf, PAGE_SIZE << order);
>>>>>> +        }
>>>>>>           WARN_ON(mem->offset);
>>>>>>           sg_dma_len(mem) = PAGE_SIZE << order;
>>>>>>
>>>>>> @@ -262,17 +272,25 @@ static struct hns_roce_hem
>>>>>> *hns_roce_alloc_hem(struct hns_roce_dev *hr_dev,
>>>>>>   void hns_roce_free_hem(struct hns_roce_dev *hr_dev, struct
>>>>>> hns_roce_hem *hem)
>>>>>>   {
>>>>>>       struct hns_roce_hem_chunk *chunk, *tmp;
>>>>>> +    void *cpu_addr;
>>>>>>       int i;
>>>>>>
>>>>>>       if (!hem)
>>>>>>           return;
>>>>>>
>>>>>>       list_for_each_entry_safe(chunk, tmp, &hem->chunk_list, list) {
>>>>>> -        for (i = 0; i < chunk->npages; ++i)
>>>>>> +        for (i = 0; i < chunk->npages; ++i) {
>>>>>> +            if (chunk->vmalloc[i].is_vmalloc_addr)
>>>>>> +                cpu_addr = chunk->vmalloc[i].vmalloc_addr;
>>>>>> +            else
>>>>>> +                cpu_addr =
>>>>>> +                   lowmem_page_address(sg_page(&chunk->mem[i]));
>>>>>> +
>>>>>>               dma_free_coherent(hr_dev->dev,
>>>>>>                      chunk->mem[i].length,
>>>>>> -                   lowmem_page_address(sg_page(&chunk->mem[i])),
>>>>>> +                   cpu_addr,
>>>>>>                      sg_dma_address(&chunk->mem[i]));
>>>>>> +        }
>>>>>>           kfree(chunk);
>>>>>>       }
>>>>>>
>>>>>> @@ -774,6 +792,12 @@ void *hns_roce_table_find(struct hns_roce_dev
>>>>>> *hr_dev,
>>>>>>
>>>>>>               if (chunk->mem[i].length > (u32)offset) {
>>>>>>                   page = sg_page(&chunk->mem[i]);
>>>>>> +                if (chunk->vmalloc[i].is_vmalloc_addr) {
>>>>>> +                    mutex_unlock(&table->mutex);
>>>>>> +                    return page ?
>>>>>> +                        chunk->vmalloc[i].vmalloc_addr
>>>>>> +                        + offset : NULL;
>>>>>> +                }
>>>>>>                   goto out;
>>>>>>               }
>>>>>>               offset -= chunk->mem[i].length;
>>>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_hem.h
>>>>>> b/drivers/infiniband/hw/hns/hns_roce_hem.h
>>>>>> index af28bbf..62d712a 100644
>>>>>> --- a/drivers/infiniband/hw/hns/hns_roce_hem.h
>>>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_hem.h
>>>>>> @@ -72,11 +72,17 @@ enum {
>>>>>>        HNS_ROCE_HEM_PAGE_SIZE  = 1 << HNS_ROCE_HEM_PAGE_SHIFT,
>>>>>>   };
>>>>>>
>>>>>> +struct hns_roce_vmalloc {
>>>>>> +    bool    is_vmalloc_addr;
>>>>>> +    void    *vmalloc_addr;
>>>>>> +};
>>>>>> +
>>>>>>   struct hns_roce_hem_chunk {
>>>>>>       struct list_head     list;
>>>>>>       int             npages;
>>>>>>       int             nsg;
>>>>>>       struct scatterlist     mem[HNS_ROCE_HEM_CHUNK_LEN];
>>>>>> +    struct hns_roce_vmalloc     vmalloc[HNS_ROCE_HEM_CHUNK_LEN];
>>>>>>   };
>>>>>>
>>>>>>   struct hns_roce_hem {
>>>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>>>>>> b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>>>>>> index b99d70a..9e19bf1 100644
>>>>>> --- a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>>>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>>>>>> @@ -1093,9 +1093,11 @@ static int hns_roce_v2_write_mtpt(void
>>>>>> *mb_buf, struct hns_roce_mr *mr,
>>>>>>   {
>>>>>>       struct hns_roce_v2_mpt_entry *mpt_entry;
>>>>>>       struct scatterlist *sg;
>>>>>> +    u64 page_addr = 0;
>>>>>>       u64 *pages;
>>>>>> +    int i = 0, j = 0;
>>>>>> +    int len = 0;
>>>>>>       int entry;
>>>>>> -    int i;
>>>>>>
>>>>>>       mpt_entry = mb_buf;
>>>>>>       memset(mpt_entry, 0, sizeof(*mpt_entry));
>>>>>> @@ -1153,14 +1155,20 @@ static int hns_roce_v2_write_mtpt(void
>>>>>> *mb_buf, struct hns_roce_mr *mr,
>>>>>>
>>>>>>       i = 0;
>>>>>>       for_each_sg(mr->umem->sg_head.sgl, sg, mr->umem->nmap, entry) {
>>>>>> -        pages[i] = ((u64)sg_dma_address(sg)) >> 6;
>>>>>> -
>>>>>> -        /* Record the first 2 entry directly to MTPT table */
>>>>>> -        if (i >= HNS_ROCE_V2_MAX_INNER_MTPT_NUM - 1)
>>>>>> -            break;
>>>>>> -        i++;
>>>>>> +        len = sg_dma_len(sg) >> PAGE_SHIFT;
>>>>>> +        for (j = 0; j < len; ++j) {
>>>>>> +            page_addr = sg_dma_address(sg) +
>>>>>> +                    (j << mr->umem->page_shift);
>>>>>> +            pages[i] = page_addr >> 6;
>>>>>> +
>>>>>> +            /* Record the first 2 entry directly to MTPT table */
>>>>>> +            if (i >= HNS_ROCE_V2_MAX_INNER_MTPT_NUM - 1)
>>>>>> +                goto found;
>>>>>> +            i++;
>>>>>> +        }
>>>>>>       }
>>>>>>
>>>>>> +found:
>>>>>>       mpt_entry->pa0_l = cpu_to_le32(lower_32_bits(pages[0]));
>>>>>>       roce_set_field(mpt_entry->byte_56_pa0_h, V2_MPT_BYTE_56_PA0_H_M,
>>>>>>                  V2_MPT_BYTE_56_PA0_H_S,
>>>>>> -- 
>>>>>> 1.9.1
>>>>>>
>>>> _______________________________________________
>>>> iommu mailing list
>>>> iommu@...ts.linux-foundation.org
>>>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>>> .
>>>
>>
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