Re: [PATCH mlx5-next 1/7] RDMA/mlx5: Don't set esc_size in user mr

Started by Leon Romanovsky on Oct 12, 2021

open the first message on its own page

Message details and related content
On Tue, Oct 12, 2021 at 11:04:33AM -0300, Jason Gunthorpe wrote:
On Tue, Oct 12, 2021 at 04:57:16PM +0300, Aharon Landau wrote:
quoted
On 10/12/2021 3:52 PM, Jason Gunthorpe wrote:
quoted
On Tue, Oct 12, 2021 at 01:26:29PM +0300, Leon Romanovsky wrote:
quoted
From: Aharon Landau <redacted>

reg_create() is used for user MRs only and should not set desc_size at
all. Attempt to set it causes to the following trace:

BUG: unable to handle page fault for address: 0000000800000000
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 5 PID: 890 Comm: ib_write_bw Not tainted 5.15.0-rc4+ #47
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:mlx5_ib_dereg_mr+0x14/0x3b0 [mlx5_ib]
Code: 48 63 cd 4c 89 f7 48 89 0c 24 e8 37 30 03 e1 48 8b 0c 24 eb a0 90 0f 1f 44 00 00 41 56 41 55 41 54 55 53 48 89 fb 48 83 ec 30 <48> 8b 2f 65 48 8b 04 25 28 00 00 00 48 89 44 24 28 31 c0 8b 87 c8
RSP: 0018:ffff88811afa3a60 EFLAGS: 00010286
RAX: 000000000000001c RBX: 0000000800000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000800000000
RBP: 0000000800000000 R08: 0000000000000000 R09: c0000000fffff7ff
R10: ffff88811afa38f8 R11: ffff88811afa38f0 R12: ffffffffa02c7ac0
R13: 0000000000000000 R14: ffff88811afa3cd8 R15: ffff88810772fa00
FS:  00007f47b9080740(0000) GS:ffff88852cd40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000800000000 CR3: 000000010761e003 CR4: 0000000000370ea0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  mlx5_ib_free_odp_mr+0x95/0xc0 [mlx5_ib]
  mlx5_ib_dereg_mr+0x128/0x3b0 [mlx5_ib]
  ib_dereg_mr_user+0x45/0xb0 [ib_core]
  ? xas_load+0x8/0x80
  destroy_hw_idr_uobject+0x1a/0x50 [ib_uverbs]
  uverbs_destroy_uobject+0x2f/0x150 [ib_uverbs]
  uobj_destroy+0x3c/0x70 [ib_uverbs]
  ib_uverbs_cmd_verbs+0x467/0xb00 [ib_uverbs]
  ? uverbs_finalize_object+0x60/0x60 [ib_uverbs]
  ? ttwu_queue_wakelist+0xa9/0xe0
  ? pty_write+0x85/0x90
  ? file_tty_write.isra.33+0x214/0x330
  ? process_echoes+0x60/0x60
  ib_uverbs_ioctl+0xa7/0x110 [ib_uverbs]
  __x64_sys_ioctl+0x10d/0x8e0
  ? vfs_write+0x17f/0x260
  do_syscall_64+0x3c/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: a639e66703ee ("RDMA/mlx5: Zero out ODP related items in the mlx5_ib_mr")
Can you explain why this is crashing?

reg_create isn't used on the ODP implicit children path.

Jason
It is not implicit ODP flow, therefore, mr->implicit_children shouldn't be
set.
It should always be initialized. That seems to be the bug here, add the
missing xa_init as well as delete the extra desc_size set:
I would expect such change in mlx5_ib_init_odp_mr().
quoted hunk
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index b4d2322e9ca564..46626e0fe08905 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1525,6 +1525,7 @@ static struct ib_mr *create_user_odp_mr(struct ib_pd *pd, u64 start, u64 length,
                ib_umem_release(&odp->umem);
                return ERR_CAST(mr);
        }
+       xa_init(&mr->implicit_children);
 
        odp->private = mr;
        err = mlx5r_store_odp_mkey(dev, &mr->mmkey);
Jason
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