diff options
| author | Vaibhav Jain <vaibhav@linux.ibm.com> | 2018-05-18 15:12:23 +0530 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-07-03 11:24:51 +0200 |
| commit | c9debbd1a5b84014d8651da82ca30651d83ca322 (patch) | |
| tree | c44cceb73baab5241a0de1d17c47e3a0f244e64e /Documentation/ABI | |
| parent | 971a55574b4789c64d43c6d34f5549c337567731 (diff) | |
cxl: Disable prefault_mode in Radix mode
commit b6c84ba22ff3a198eb8d5552cf9b8fda1d792e54 upstream.
Currently we see a kernel-oops reported on Power-9 while attaching a
context to an AFU, with radix-mode and sysfs attr 'prefault_mode' set
to anything other than 'none'. The backtrace of the oops is of this
form:
Unable to handle kernel paging request for data at address 0x00000080
Faulting instruction address: 0xc00800000bcf3b20
cpu 0x1: Vector: 300 (Data Access) at [c00000037f003800]
pc: c00800000bcf3b20: cxl_load_segment+0x178/0x290 [cxl]
lr: c00800000bcf39f0: cxl_load_segment+0x48/0x290 [cxl]
sp: c00000037f003a80
msr: 9000000000009033
dar: 80
dsisr: 40000000
current = 0xc00000037f280000
paca = 0xc0000003ffffe600 softe: 3 irq_happened: 0x01
pid = 3529, comm = afp_no_int
<snip>
cxl_prefault+0xfc/0x248 [cxl]
process_element_entry_psl9+0xd8/0x1a0 [cxl]
cxl_attach_dedicated_process_psl9+0x44/0x130 [cxl]
native_attach_process+0xc0/0x130 [cxl]
afu_ioctl+0x3f4/0x5e0 [cxl]
do_vfs_ioctl+0xdc/0x890
ksys_ioctl+0x68/0xf0
sys_ioctl+0x40/0xa0
system_call+0x58/0x6c
The issue is caused as on Power-8 the AFU attr 'prefault_mode' was
used to improve initial storage fault performance by prefaulting
process segments. However on Power-9 with radix mode we don't have
Storage-Segments that we can prefault. Also prefaulting process Pages
will be too costly and fine-grained.
Hence, since the prefaulting mechanism doesn't makes sense of
radix-mode, this patch updates prefault_mode_store() to not allow any
other value apart from CXL_PREFAULT_NONE when radix mode is enabled.
Fixes: f24be42aab37 ("cxl: Add psl9 specific code")
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-class-cxl | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-cxl b/Documentation/ABI/testing/sysfs-class-cxl index 640f65e79ef1..267920a1874b 100644 --- a/Documentation/ABI/testing/sysfs-class-cxl +++ b/Documentation/ABI/testing/sysfs-class-cxl @@ -69,7 +69,9 @@ Date: September 2014 Contact: linuxppc-dev@lists.ozlabs.org Description: read/write Set the mode for prefaulting in segments into the segment table - when performing the START_WORK ioctl. Possible values: + when performing the START_WORK ioctl. Only applicable when + running under hashed page table mmu. + Possible values: none: No prefaulting (default) work_element_descriptor: Treat the work element descriptor as an effective address and |