linux-kernel - Re: [PATCH v5 0/3] selftests/lam: get_user additions and LAM enabled check

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Message-ID: <1cf82baf-1937-42e9-add6-2a161fea434f@linuxfoundation.org>
Date: Thu, 23 Jan 2025 14:52:51 -0700
From: Shuah Khan <skhan@...uxfoundation.org>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>, shuah@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 kirill@...temov.name, hpa@...or.com, x86@...nel.org,
 dave.hansen@...ux.intel.com, bp@...en8.de, mingo@...hat.com,
 tglx@...utronix.de, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v5 0/3] selftests/lam: get_user additions and LAM enabled
 check

On 1/15/25 02:06, Maciej Wieczor-Retman wrote:
> Hello Shuah, I'd like to bump this series for visibility and ask if you still
> consider these patches okay to merge?
> 
> Just checked and there were no conflicts after applying it on the newest
> kselftest-next.
> 

This is x86 test and usually goes through x86 tree. I can take this
through kselftest tree if I get an ack from x86 maintainer.

> On 2024-11-27 at 18:35:28 +0100, Maciej Wieczor-Retman wrote:
>> 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 | 120 ++++++++++++++++++++++++++++--
>> 1 file changed, 115 insertions(+), 5 deletions(-)
>>
>> -- 
>> 2.47.1
>>
> 

thanks,
-- Shuah