linux-kernel - [PATCH v4 0/3] selftests/lam: get_user additions and LAM enabled check

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Message-ID: <cover.1732627541.git.maciej.wieczor-retman@intel.com>
Date: Tue, 26 Nov 2024 14:34:47 +0100
From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
To: shuah@...nel.org,
	hpa@...or.com,
	x86@...nel.org,
	dave.hansen@...ux.intel.com,
	bp@...en8.de,
	mingo@...hat.com,
	tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	kirill@...temov.name,
	maciej.wieczor-retman@...el.com
Subject: [PATCH v4 0/3] selftests/lam: get_user additions and LAM enabled check

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/

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 | 122 ++++++++++++++++++++++++++++--
 1 file changed, 117 insertions(+), 5 deletions(-)

-- 
2.47.1