mbox series

[v6,0/3] selftests/lam: get_user additions and LAM enabled check

Message ID cover.1737990375.git.maciej.wieczor-retman@intel.com (mailing list archive)
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Series selftests/lam: get_user additions and LAM enabled check | expand

Message

Maciej Wieczor-Retman Jan. 27, 2025, 3:31 p.m. UTC 
Changes in v6:
- Move la57 check to using mmap().
- Merge kernel_has_lam() and cpu_has_lam() into lam_is_available() since
  the syscall (if CONFIG_ADDRESS_MASKING is set) and cpuid check
  provides the same information.

Recent change in how get_user() handles pointers [1] has a specific case
for LAM. It assigns a different bitmask that's later used to check
whether a pointer comes from userland in get_user().

While currently commented out (until LASS [2] is merged into the kernel)
it's worth making changes to the LAM selftest ahead of time.

Modify cpu_has_la57() so it provides current paging level information
instead of the cpuid one.

Add test case to LAM that utilizes a ioctl (FIOASYNC) syscall which uses
get_user() in its implementation. Execute the syscall with differently
tagged pointers to verify that valid user pointers are passing through
and invalid kernel/non-canonical pointers are not.

Also to avoid unhelpful test failures add a check in main() to skip
running tests if LAM was not compiled into the kernel.

Code was tested on a Sierra Forest Xeon machine that's LAM capable. The
test was ran without issues with both the LAM lines from [1] untouched
and commented out. The test was also ran without issues with LAM_SUP
both enabled and disabled.

4/5 level pagetables code paths were also successfully tested in Simics
on a 5-level capable machine.

[1] https://lore.kernel.org/all/20241024013214.129639-1-torvalds@linux-foundation.org/
[2] https://lore.kernel.org/all/20241028160917.1380714-1-alexander.shishkin@linux.intel.com/

Previous series entries:
[v1] https://lore.kernel.org/all/20241029141421.715686-1-maciej.wieczor-retman@intel.com/
[v2] https://lore.kernel.org/all/20241121090651.254054-1-maciej.wieczor-retman@intel.com/
[v3] https://lore.kernel.org/all/20241122085521.270802-1-maciej.wieczor-retman@intel.com/
[v4] https://lore.kernel.org/all/cover.1732627541.git.maciej.wieczor-retman@intel.com/
[v5] https://lore.kernel.org/all/cover.1732728879.git.maciej.wieczor-retman@intel.com/

Maciej Wieczor-Retman (3):
  selftests/lam: Move cpu_has_la57() to use cpuinfo flag
  selftests/lam: Skip test if LAM is disabled
  selftests/lam: Test get_user() LAM pointer handling

 tools/testing/selftests/x86/lam.c | 147 +++++++++++++++++++++++++++---
 1 file changed, 136 insertions(+), 11 deletions(-)