Linux kernel source tree
a9f4fa3a7e
Currently we treat EFAULT from hmm_range_fault() as a non-fatal error
when called from xe_vm_userptr_pin() with the idea that we want to avoid
killing the entire vm and chucking an error, under the assumption that
the user just did an unmap or something, and has no intention of
actually touching that memory from the GPU. At this point we have
already zapped the PTEs so any access should generate a page fault, and
if the pin fails there also it will then become fatal.
However it looks like it's possible for the userptr vma to still be on
the rebind list in preempt_rebind_work_func(), if we had to retry the
pin again due to something happening in the caller before we did the
rebind step, but in the meantime needing to re-validate the userptr and
this time hitting the EFAULT.
This explains an internal user report of hitting:
[ 191.738349] WARNING: CPU: 1 PID: 157 at drivers/gpu/drm/xe/xe_res_cursor.h:158 xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe]
[ 191.738551] Workqueue: xe-ordered-wq preempt_rebind_work_func [xe]
[ 191.738616] RIP: 0010:xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe]
[ 191.738690] Call Trace:
[ 191.738692] <TASK>
[ 191.738694] ? show_regs+0x69/0x80
[ 191.738698] ? __warn+0x93/0x1a0
[ 191.738703] ? xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe]
[ 191.738759] ? report_bug+0x18f/0x1a0
[ 191.738764] ? handle_bug+0x63/0xa0
[ 191.738767] ? exc_invalid_op+0x19/0x70
[ 191.738770] ? asm_exc_invalid_op+0x1b/0x20
[ 191.738777] ? xe_pt_stage_bind.constprop.0+0x60a/0x6b0 [xe]
[ 191.738834] ? ret_from_fork_asm+0x1a/0x30
[ 191.738849] bind_op_prepare+0x105/0x7b0 [xe]
[ 191.738906] ? dma_resv_reserve_fences+0x301/0x380
[ 191.738912] xe_pt_update_ops_prepare+0x28c/0x4b0 [xe]
[ 191.738966] ? kmemleak_alloc+0x4b/0x80
[ 191.738973] ops_execute+0x188/0x9d0 [xe]
[ 191.739036] xe_vm_rebind+0x4ce/0x5a0 [xe]
[ 191.739098] ? trace_hardirqs_on+0x4d/0x60
[ 191.739112] preempt_rebind_work_func+0x76f/0xd00 [xe]
Followed by NPD, when running some workload, since the sg was never
actually populated but the vma is still marked for rebind when it should
be skipped for this special EFAULT case. This is confirmed to fix the
user report.
v2 (MattB):
- Move earlier.
v3 (MattB):
- Update the commit message to make it clear that this indeed fixes the
issue.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.