This patch fixed the potential illegal operation when using the
extend sge buffer cross page in post send operation. The bug
will cause the calltrace as below.

[ 3302.922107] Unable to handle kernel paging request at virtual address ffff00003b3a0004
[ 3302.930009] Mem abort info:
[ 3302.932790]   Exception class = DABT (current EL), IL = 32 bits
[ 3302.938695]   SET = 0, FnV = 0
[ 3302.941735]   EA = 0, S1PTW = 0
[ 3302.944863] Data abort info:
[ 3302.947729]   ISV = 0, ISS = 0x00000047
[ 3302.951551]   CM = 0, WnR = 1
[ 3302.954506] swapper pgtable: 4k pages, 48-bit VAs, pgd = ffff000009ea5000
[ 3302.961279] [ffff00003b3a0004] *pgd=00000023dfffe003, *pud=00000023dfffd003, *pmd=00000022dc84c003, *pte=0000000000000000
[ 3302.972224] Internal error: Oops: 96000047 [#1] SMP
[ 3302.999509] CPU: 9 PID: 19628 Comm: roce_test_main Tainted: G           OE   4.14.10 #1
[ 3303.007498] task: ffff80234df78000 task.stack: ffff00000f640000
[ 3303.013412] PC is at hns_roce_v2_post_send+0x690/0xe20 [hns_roce_pci]
[ 3303.019843] LR is at hns_roce_v2_post_send+0x658/0xe20 [hns_roce_pci]
[ 3303.026269] pc : [<ffff0000020694f8>] lr : [<ffff0000020694c0>] pstate: 804001c9
[ 3303.033649] sp : ffff00000f643870
[ 3303.036951] x29: ffff00000f643870 x28: ffff80232bfa9c00
[ 3303.042250] x27: ffff80234d909380 x26: ffff00003b37f0c0
[ 3303.047549] x25: 0000000000000000 x24: 0000000000000003
[ 3303.052848] x23: 0000000000000000 x22: 0000000000000000
[ 3303.058148] x21: 0000000000000101 x20: 0000000000000001
[ 3303.063447] x19: ffff80236163f800 x18: 0000000000000000
[ 3303.068746] x17: 0000ffff86b76fc8 x16: ffff000008301600
[ 3303.074045] x15: 000020a51c000000 x14: 3128726464615f65
[ 3303.079344] x13: 746f6d6572202c29 x12: 303035312879656b
[ 3303.084643] x11: 723a6f666e692072 x10: 573a6f666e693a5d
[ 3303.089943] x9 : 0000000000000004 x8 : ffff8023ce38b000
[ 3303.095242] x7 : ffff8023ce38b320 x6 : 0000000000000418
[ 3303.100541] x5 : ffff80232bfa9cc8 x4 : 0000000000000030
[ 3303.105839] x3 : 0000000000000100 x2 : 0000000000000200
[ 3303.111138] x1 : 0000000000000320 x0 : ffff00003b3a0000
[ 3303.116438] Process roce_test_main (pid: 19628, stack limit = 0xffff00000f640000)
[ 3303.123906] Call trace:
[ 3303.126339] Exception stack(0xffff00000f643730 to 0xffff00000f643870)
[ 3303.215790] [<ffff0000020694f8>] hns_roce_v2_post_send+0x690/0xe20 [hns_roce_pci]
[ 3303.223293] [<ffff0000021c3750>] rt_ktest_post_send+0x5d0/0x8b8 [rdma_test]
[ 3303.230261] [<ffff0000021b3234>] exec_send_cmd+0x664/0x1350 [rdma_test]
[ 3303.236881] [<ffff0000021b8b30>] rt_ktest_dispatch_cmd_3+0x1510/0x3790 [rdma_test]
[ 3303.244455] [<ffff0000021bae54>] rt_ktest_dispatch_cmd_2+0xa4/0x118 [rdma_test]
[ 3303.251770] [<ffff0000021bafec>] rt_ktest_dispatch_cmd+0x124/0xaa8 [rdma_test]
[ 3303.258997] [<ffff0000021bbc3c>] rt_ktest_dev_write+0x2cc/0x568 [rdma_test]
[ 3303.265947] [<ffff0000082ad688>] __vfs_write+0x60/0x18c
[ 3303.271158] [<ffff0000082ad998>] vfs_write+0xa8/0x198
[ 3303.276196] [<ffff0000082adc7c>] SyS_write+0x6c/0xd4
[ 3303.281147] Exception stack(0xffff00000f643ec0 to 0xffff00000f644000)
[ 3303.287573] 3ec0: 0000000000000003 0000fffffc85faa8 0000000000004e60 0000000000000000
[ 3303.295388] 3ee0: 0000000021fb2000 000000000000ffff eff0e3efe4e58080 0000fffffcc724fe
[ 3303.303204] 3f00: 0000000000000040 1999999999999999 0101010101010101 0000000000000038
[ 3303.311019] 3f20: 0000000000000005 ffffffffffffffff 0d73757461747320 ffffffffffffffff
[ 3303.318835] 3f40: 0000000000000000 0000000000459b00 0000fffffc85e360 000000000043d788
[ 3303.326650] 3f60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 3303.334465] 3f80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 3303.342281] 3fa0: 0000000000000000 0000fffffc85e570 0000000000438804 0000fffffc85e570
[ 3303.350096] 3fc0: 0000ffff8553f618 0000000080000000 0000000000000003 0000000000000040
[ 3303.357911] 3fe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 3303.365729] [<ffff000008083808>] __sys_trace_return+0x0/0x4
[ 3303.371288] Code: b94008e9 34000129 b9400ce2 110006b5 (b9000402)
[ 3303.377377] ---[ end trace fd5ab98b3325cf9a ]---
Reported-by: NJie Chen <chenjie103@huawei.com>
Reported-by: NXiping Zhang (Francis) <zhangxiping3@huawei.com>
Fixes: b1c15835("RDMA/hns: Get rid of virt_to_page and vmap calls after dma_alloc_coherent")
Signed-off-by: NWei Hu (Xavier) <xavier.huwei@huawei.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>