iommu/amd: Improve page fault error reporting

In the Linux kernel, the following vulnerability has been resolved:

iommu/amd: Improve page fault error reporting

If IOMMU domain for device group is not setup properly then we may hit

IOMMU page fault. Current page fault handler assumes that domain is

always setup and it will hit NULL pointer derefence (see below sample log).

Lets check whether domain is setup or not and log appropriate message.

Sample log:

----------

amdgpu 0000:00:01.0: amdgpu: SE 1, SH per SE 1, CU per SH 8, active_cu_number 6

BUG: kernel NULL pointer dereference, address: 0000000000000058

#PF: supervisor read access in kernel mode

#PF: error_code(0x0000) - not-present page

PGD 0 P4D 0

Oops: 0000 [#1] PREEMPT SMP NOPTI

CPU: 2 PID: 56 Comm: irq/24-AMD-Vi Not tainted 6.2.0-rc2+ #89

Hardware name: xxx

RIP: 0010:report_iommu_fault+0x11/0x90

[...]

Call Trace:

<TASK>

amd_iommu_int_thread+0x60c/0x760

? __pfx_irq_thread_fn+0x10/0x10

irq_thread_fn+0x1f/0x60

irq_thread+0xea/0x1a0

? preempt_count_add+0x6a/0xa0

? __pfx_irq_thread_dtor+0x10/0x10

? __pfx_irq_thread+0x10/0x10

kthread+0xe9/0x110

? __pfx_kthread+0x10/0x10

ret_from_fork+0x2c/0x50

</TASK>

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