From: Dave Hansen <dave.hansen@intel.com>
To: ira.weiny@intel.com, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linux-doc@vger.kernel.org, linux-nvdimm@lists.01.org,
linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
Dan Williams <dan.j.williams@intel.com>,
Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [PATCH V3 10/10] x86/pks: Add PKS test code
Date: Thu, 17 Dec 2020 12:55:39 -0800 [thread overview]
Message-ID: <570ead2a-ff41-e730-d61d-0f59c67b1903@intel.com> (raw)
In-Reply-To: <20201106232908.364581-11-ira.weiny@intel.com>
On 11/6/20 3:29 PM, ira.weiny@intel.com wrote:
> + /* Arm for context switch test */
> + write(fd, "1", 1);
> +
> + /* Context switch out... */
> + sleep(4);
> +
> + /* Check msr restored */
> + write(fd, "2", 1);
These are always tricky. What you ideally want here is:
1. Switch away from this task to a non-PKS task, or
2. Switch from this task to a PKS-using task, but one which has a
different PKS value
then, switch back to this task and make sure PKS maintained its value.
*But*, there's no absolute guarantee that another task will run. It
would not be totally unreasonable to have the kernel just sit in a loop
without context switching here if no other tasks can run.
The only way you *know* there is a context switch is by having two tasks
bound to the same logical CPU and make sure they run one after another.
This just gets itself into a state where it *CAN* context switch and
prays that one will happen.
You can also run a bunch of these in parallel bound to a single CPU.
That would also give you higher levels of assurance that *some* context
switch happens at sleep().
One critical thing with these tests is to sabotage the kernel and then
run them and make *sure* they fail. Basically, if you screw up, do they
actually work to catch it?
next prev parent reply other threads:[~2020-12-17 20:56 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-06 23:28 [PATCH V3 00/10] PKS: Add Protection Keys Supervisor (PKS) support V3 ira.weiny
2020-11-06 23:28 ` [PATCH V3 01/10] x86/pkeys: Create pkeys_common.h ira.weiny
2020-11-06 23:29 ` [PATCH V3 02/10] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support ira.weiny
2020-11-06 23:29 ` [PATCH V3 03/10] x86/pks: Add PKS defines and Kconfig options ira.weiny
2020-11-06 23:29 ` [PATCH V3 04/10] x86/pks: Preserve the PKRS MSR on context switch ira.weiny
2020-12-17 14:50 ` Thomas Gleixner
2020-12-17 22:43 ` Thomas Gleixner
2020-12-18 13:57 ` Thomas Gleixner
2020-12-18 19:20 ` Dan Williams
2020-12-18 21:06 ` Thomas Gleixner
2020-12-18 21:58 ` Dan Williams
2020-12-18 22:44 ` Thomas Gleixner
2020-12-18 19:42 ` Ira Weiny
2020-12-18 20:10 ` Dave Hansen
2020-12-18 21:30 ` Thomas Gleixner
2020-12-18 4:05 ` Ira Weiny
2020-12-17 20:41 ` [NEEDS-REVIEW] " Dave Hansen
2020-12-18 4:10 ` Ira Weiny
2020-12-18 15:33 ` Dave Hansen
2020-11-06 23:29 ` [PATCH V3 05/10] x86/entry: Pass irqentry_state_t by reference ira.weiny
2020-11-15 18:58 ` Thomas Gleixner
2020-11-16 18:49 ` Ira Weiny
2020-11-16 20:36 ` Thomas Gleixner
2020-11-24 6:09 ` [PATCH V3.1] entry: " ira.weiny
2020-12-11 22:14 ` Andy Lutomirski
2020-12-16 1:32 ` Ira Weiny
2020-12-16 2:09 ` Andy Lutomirski
2020-12-17 0:38 ` Ira Weiny
2020-12-17 13:07 ` Thomas Gleixner
2020-12-17 13:19 ` Peter Zijlstra
2020-12-17 15:35 ` Andy Lutomirski
2020-12-17 16:58 ` Thomas Gleixner
2020-11-06 23:29 ` [PATCH V3 06/10] x86/entry: Preserve PKRS MSR across exceptions ira.weiny
2020-12-17 15:28 ` Thomas Gleixner
2020-11-06 23:29 ` [PATCH V3 07/10] x86/fault: Report the PKRS state on fault ira.weiny
2020-11-06 23:29 ` [PATCH V3 08/10] x86/pks: Add PKS kernel API ira.weiny
2020-12-23 20:39 ` Randy Dunlap
2020-11-06 23:29 ` [PATCH V3 09/10] x86/pks: Enable Protection Keys Supervisor (PKS) ira.weiny
2020-11-06 23:29 ` [PATCH V3 10/10] x86/pks: Add PKS test code ira.weiny
2020-12-17 20:55 ` Dave Hansen [this message]
2020-12-18 4:05 ` Ira Weiny
2020-12-18 16:59 ` Dan Williams
2020-12-07 22:14 ` [PATCH V3 00/10] PKS: Add Protection Keys Supervisor (PKS) support V3 Ira Weiny
2020-12-08 15:55 ` Thomas Gleixner
2020-12-08 17:22 ` Ira Weiny
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