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Message-ID: <95b1875c-fe87-4941-9242-551fb9546ccc@gmail.com>
Date: Sat, 24 May 2025 22:15:43 +0900
From: Daisuke Matsuda <dskmtsd@...il.com>
To: Zhu Yanjun <yanjun.zhu@...ux.dev>, linux-kernel@...r.kernel.org,
linux-rdma@...r.kernel.org, leon@...nel.org, jgg@...pe.ca,
zyjzyj2000@...il.com
Cc: hch@...radead.org
Subject: Re: [PATCH for-next v1] RDMA/core: Avoid hmm_dma_map_alloc() for
virtual DMA devices
On 2025/05/24 16:52, Zhu Yanjun wrote:
> 在 2025/5/24 9:31, Zhu Yanjun 写道:
>> 在 2025/5/23 20:47, Daisuke Matsuda 写道:
>>> Drivers such as rxe, which use virtual DMA, must not call into the DMA
>>> mapping core since they lack physical DMA capabilities. Otherwise, a NULL
>>> pointer dereference is observed as shown below. This patch ensures the RDMA
>>> core handles virtual and physical DMA paths appropriately.
>>>
>>> This fixes the following kernel oops:
>>>
>>> BUG: kernel NULL pointer dereference, address: 00000000000002fc
>>> #PF: supervisor read access in kernel mode
>>> #PF: error_code(0x0000) - not-present page
>>> PGD 1028eb067 P4D 1028eb067 PUD 105da0067 PMD 0
>>> Oops: Oops: 0000 [#1] SMP NOPTI
>>> CPU: 3 UID: 1000 PID: 1854 Comm: python3 Tainted: G W 6.15.0-rc1+ #11 PREEMPT(voluntary)
>>> Tainted: [W]=WARN
>>> Hardware name: Trigkey Key N/Key N, BIOS KEYN101 09/02/2024
>>> RIP: 0010:hmm_dma_map_alloc+0x25/0x100
>>> Code: 90 90 90 90 90 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 49 89 d6 49 c1 e6 0c 41 55 41 54 53 49 39 ce 0f 82 c6 00 00 00 49 89 fc <f6> 87 fc 02 00 00 20 0f 84 af 00 00 00 49 89 f5 48 89 d3 49 89 cf
>>> RSP: 0018:ffffd3d3420eb830 EFLAGS: 00010246
>>> RAX: 0000000000001000 RBX: ffff8b727c7f7400 RCX: 0000000000001000
>>> RDX: 0000000000000001 RSI: ffff8b727c7f74b0 RDI: 0000000000000000
>>> RBP: ffffd3d3420eb858 R08: 0000000000000000 R09: 0000000000000000
>>> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
>>> R13: 00007262a622a000 R14: 0000000000001000 R15: ffff8b727c7f74b0
>>> FS: 00007262a62a1080(0000) GS:ffff8b762ac3e000(0000) knlGS:0000000000000000
>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: 00000000000002fc CR3: 000000010a1f0004 CR4: 0000000000f72ef0
>>> PKRU: 55555554
>>> Call Trace:
>>> <TASK>
>>> ib_init_umem_odp+0xb6/0x110 [ib_uverbs]
>>> ib_umem_odp_get+0xf0/0x150 [ib_uverbs]
>>> rxe_odp_mr_init_user+0x71/0x170 [rdma_rxe]
>>> rxe_reg_user_mr+0x217/0x2e0 [rdma_rxe]
>>> ib_uverbs_reg_mr+0x19e/0x2e0 [ib_uverbs]
>>> ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xd9/0x150 [ib_uverbs]
>>> ib_uverbs_cmd_verbs+0xd19/0xee0 [ib_uverbs]
>>> ? mmap_region+0x63/0xd0
>>> ? __pfx_ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x10/0x10 [ib_uverbs]
>>> ib_uverbs_ioctl+0xba/0x130 [ib_uverbs]
>>> __x64_sys_ioctl+0xa4/0xe0
>>> x64_sys_call+0x1178/0x2660
>>> do_syscall_64+0x7e/0x170
>>> ? syscall_exit_to_user_mode+0x4e/0x250
>>> ? do_syscall_64+0x8a/0x170
>>> ? do_syscall_64+0x8a/0x170
>>> ? syscall_exit_to_user_mode+0x4e/0x250
>>> ? do_syscall_64+0x8a/0x170
>>> ? syscall_exit_to_user_mode+0x4e/0x250
>>> ? do_syscall_64+0x8a/0x170
>>> ? do_user_addr_fault+0x1d2/0x8d0
>>> ? irqentry_exit_to_user_mode+0x43/0x250
>>> ? irqentry_exit+0x43/0x50
>>> ? exc_page_fault+0x93/0x1d0
>>> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>>> RIP: 0033:0x7262a6124ded
>>> Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00
>>> RSP: 002b:00007fffd08c3960 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>>> RAX: ffffffffffffffda RBX: 00007fffd08c39f0 RCX: 00007262a6124ded
>>> RDX: 00007fffd08c3a10 RSI: 00000000c0181b01 RDI: 0000000000000007
>>> RBP: 00007fffd08c39b0 R08: 0000000014107820 R09: 00007fffd08c3b44
>>> R10: 000000000000000c R11: 0000000000000246 R12: 00007fffd08c3b44
>>> R13: 000000000000000c R14: 00007fffd08c3b58 R15: 0000000014107960
>>> </TASK>
>>>
>>> Fixes: 1efe8c0670d6 ("RDMA/core: Convert UMEM ODP DMA mapping to caching IOVA and page linkage")
>>> Closes: https://lore.kernel.org/ all/3e8f343f-7d66-4f7a-9f08-3910623e322f@...il.com/
>>> Signed-off-by: Daisuke Matsuda <dskmtsd@...il.com>
>>> ---
>>> drivers/infiniband/core/device.c | 24 ++++++++++++++++++++++++
>>> drivers/infiniband/core/umem_odp.c | 6 +++---
>>> include/rdma/ib_verbs.h | 12 ++++++++++++
>>> 3 files changed, 39 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/ core/device.c
>>> index b4e3e4beb7f4..8be4797c66ec 100644
>>> --- a/drivers/infiniband/core/device.c
>>> +++ b/drivers/infiniband/core/device.c
>>> @@ -2864,6 +2864,30 @@ int ib_dma_virt_map_sg(struct ib_device *dev, struct scatterlist *sg, int nents)
>>> return nents;
>>> }
>>> EXPORT_SYMBOL(ib_dma_virt_map_sg);
>>> +int ib_dma_virt_map_alloc(struct device *dev, struct hmm_dma_map *map,
>>> + size_t nr_entries, size_t dma_entry_size)
>>> +{
>>> + if (!(nr_entries * PAGE_SIZE / dma_entry_size))
>>> + return -EINVAL;
>>> +
>>> + map->dma_entry_size = dma_entry_size;
>>> + map->pfn_list = kvcalloc(nr_entries, sizeof(*map->pfn_list),
>>> + GFP_KERNEL | __GFP_NOWARN);
>>> + if (!map->pfn_list)
>>> + return -ENOMEM;
>>> +
>>> + map->dma_list = kvcalloc(nr_entries, sizeof(*map->dma_list),
>>> + GFP_KERNEL | __GFP_NOWARN);
>>> + if (!map->dma_list)
>>> + goto err_dma;
>>> +
>>> + return 0;
>>> +
>>> +err_dma:
>>> + kvfree(map->pfn_list);
>>> + return -ENOMEM;
>>> +}
>>> +EXPORT_SYMBOL(ib_dma_virt_map_alloc);
>>> #endif /* CONFIG_INFINIBAND_VIRT_DMA */
>>> static const struct rdma_nl_cbs ibnl_ls_cb_table[RDMA_NL_LS_NUM_OPS] = {
>>> diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/ core/umem_odp.c
>>> index 51d518989914..aa03f3fc84d0 100644
>>> --- a/drivers/infiniband/core/umem_odp.c
>>> +++ b/drivers/infiniband/core/umem_odp.c
>>> @@ -75,9 +75,9 @@ static int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
>>> if (unlikely(end < page_size))
>>> return -EOVERFLOW;
>>> - ret = hmm_dma_map_alloc(dev->dma_device, &umem_odp->map,
>>> - (end - start) >> PAGE_SHIFT,
>>> - 1 << umem_odp->page_shift);
>>> + ret = ib_dma_map_alloc(dev, &umem_odp->map,
>>> + (end - start) >> PAGE_SHIFT,
>>> + 1 << umem_odp->page_shift);
>>> if (ret)
>>> return ret;
>>> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
>>> index b06a0ed81bdd..10813f348b99 100644
>>> --- a/include/rdma/ib_verbs.h
>>> +++ b/include/rdma/ib_verbs.h
>>> @@ -36,6 +36,7 @@
>>> #include <linux/irqflags.h>
>>> #include <linux/preempt.h>
>>> #include <linux/dim.h>
>>> +#include <linux/hmm-dma.h>
>>> #include <uapi/rdma/ib_user_verbs.h>
>>> #include <rdma/rdma_counter.h>
>>> #include <rdma/restrack.h>
>>> @@ -4221,6 +4222,17 @@ static inline void ib_dma_unmap_sg_attrs(struct ib_device *dev,
>>> dma_attrs);
>>> }
>>> +int ib_dma_virt_map_alloc(struct device *dev, struct hmm_dma_map *map,
>>> + size_t nr_entries, size_t dma_entry_size);
>>> +static inline int ib_dma_map_alloc(struct ib_device *dev, struct hmm_dma_map *map,
>>> + size_t nr_entries, size_t dma_entry_size)
>>> +{
>>> + if (ib_uses_virt_dma(dev))
>>> + return ib_dma_virt_map_alloc(dev->dma_device, map, nr_entries,
>>> + dma_entry_size);
>>
>> Other emulated RDMA devices driver also call ib_dma_virt_map_alloc?
>> Only rxe will call ib_dma_virt_map_alloc?
Only rxe will call ib_dma_virt_map_alloc()
because currently only mlx5 and rxe will use ib_dma_map_alloc().
>
> As I know, other emulated RDMA driver also implemented ODP, and with the current hmm_dma_map_alloc, it can work well.
> So in the above "if (ib_uses_virt_dma(dev))", changed to if (rxe_dev), then go to call ib_dma_virt_map_alloc.
Only mlx5 and rxe support ODP. While hmm_dma_map_alloc() works fine for mlx5,
it cannot be used for any drivers under drivers/infiniband/sw/ because they all set
dma_device to NULL in ib_register_device().
So changing the condition to if (rxe_dev) makes the code too specific.
To my understanding, it's generally discouraged to add code in the RDMA core
that targets a specific implementation.
I have just realized that we can remove an argument "struct device"
from ib_dma_virt_map_alloc(). I will post the v2 to fix this.
Thanks,
Daisuke
>
> Yanjun.Zhu
>
>>
>> Zhu Yanjun
>>
>>> + return hmm_dma_map_alloc(dev->dma_device, map, nr_entries, dma_entry_size);
>>> +}
>>> +
>>> /**
>>> * ib_dma_map_sgtable_attrs - Map a scatter/gather table to DMA addresses
>>> * @dev: The device for which the DMA addresses are to be created
>>
>
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