From: "Luck, Tony" <tony.luck@intel.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>,
"Christopherson, Sean J" <sean.j.christopherson@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
"Yu, Fenghua" <fenghua.yu@intel.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>, "Raj, Ashok" <ashok.raj@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v12] x86/split_lock: Enable split lock detection by kernel
Date: Wed, 22 Jan 2020 17:23:17 -0800 [thread overview]
Message-ID: <20200123012317.GA21843@agluck-desk2.amr.corp.intel.com> (raw)
In-Reply-To: <20200123004507.GA2403906@rani.riverdale.lan>
On Wed, Jan 22, 2020 at 07:45:08PM -0500, Arvind Sankar wrote:
> On Wed, Jan 22, 2020 at 11:24:34PM +0000, Luck, Tony wrote:
> > >> +static enum split_lock_detect_state sld_state = sld_warn;
> > >> +
> > >
> > > This sets sld_state to sld_warn even on CPUs that don't support
> > > split-lock detection. split_lock_init will then try to read/write the
> > > MSR to turn it on. Would it be better to initialize it to sld_off and
> > > set it to sld_warn in split_lock_setup instead, which is only called if
> > > the CPU supports the feature?
> >
> > I've lost some bits of this patch series somewhere along the way :-( There
> > was once code to decide whether the feature was supported (either with
> > x86_match_cpu() for a couple of models, or using the architectural test
> > based on some MSR bits. I need to dig that out and put it back in. Then
> > stuff can check X86_FEATURE_SPLIT_LOCK before wandering into code
> > that messes with MSRs
>
> That code is still there (cpu_set_core_cap_bits). The issue is that with
> the initialization here, nothing ever sets sld_state to sld_off if the
> feature isn't supported.
>
> v10 had a corresponding split_lock_detect_enabled that was
> 0-initialized, but Peter's patch as he sent out had the flag initialized
> to sld_warn.
Ah yes. Maybe the problem is that split_lock_init() is only
called on systems that support split loc detect, while we call
split_lock_init() unconditionally.
What if we start with sld_state = sld_off, and then have split_lock_setup
set it to either sld_warn, or whatever the user chose on the command
line. Patch below (on top of patch so you can see what I'm saying,
but will just merge it in for next version.
-Tony
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 7478bebcd735..b6046ccfa372 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -39,7 +39,13 @@ enum split_lock_detect_state {
sld_fatal,
};
-static enum split_lock_detect_state sld_state = sld_warn;
+/*
+ * Default to sld_off because most systems do not support
+ * split lock detection. split_lock_setup() will switch this
+ * to sld_warn, and then check to see if there is a command
+ * line override.
+ */
+static enum split_lock_detect_state sld_state = sld_off;
/*
* Just in case our CPU detection goes bad, or you have a weird system,
@@ -1017,10 +1023,11 @@ static inline bool match_option(const char *arg, int arglen, const char *opt)
static void __init split_lock_setup(void)
{
- enum split_lock_detect_state sld = sld_state;
+ enum split_lock_detect_state sld;
char arg[20];
int i, ret;
+ sld_state = sld = sld_warn;
setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT);
ret = cmdline_find_option(boot_command_line, "split_lock_ac",
next prev parent reply other threads:[~2020-01-23 1:23 UTC|newest]
Thread overview: 145+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-21 0:53 [PATCH v10 0/6] Enable split lock detection for real time and debug Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 1/6] x86/msr-index: Add two new MSRs Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 2/6] x86/cpufeatures: Enumerate the IA32_CORE_CAPABILITIES MSR Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 3/6] x86/split_lock: Enumerate split lock detection by " Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 4/6] x86/split_lock: Enumerate split lock detection if the IA32_CORE_CAPABILITIES MSR is not supported Fenghua Yu
2019-11-21 22:07 ` Andy Lutomirski
2019-11-22 0:37 ` Fenghua Yu
2019-11-22 2:13 ` Andy Lutomirski
2019-11-22 9:46 ` Peter Zijlstra
2019-11-21 0:53 ` [PATCH v10 5/6] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-11-21 22:10 ` Andy Lutomirski
2019-11-21 23:14 ` Fenghua Yu
2019-11-21 23:12 ` Andy Lutomirski
2019-11-21 0:53 ` [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter Fenghua Yu
2019-11-21 6:04 ` Ingo Molnar
2019-11-21 13:01 ` Peter Zijlstra
2019-11-21 13:15 ` Peter Zijlstra
2019-11-21 21:51 ` Luck, Tony
2019-11-21 22:24 ` Andy Lutomirski
2019-11-21 22:29 ` Luck, Tony
2019-11-21 23:18 ` Andy Lutomirski
2019-11-21 23:53 ` Fenghua Yu
2019-11-22 1:52 ` Sean Christopherson
2019-11-22 2:21 ` Andy Lutomirski
2019-11-22 2:39 ` Xiaoyao Li
2019-11-22 2:57 ` Andy Lutomirski
2019-11-21 23:55 ` Luck, Tony
2019-11-22 0:55 ` Luck, Tony
2019-11-22 10:08 ` Peter Zijlstra
2019-11-21 16:14 ` Fenghua Yu
2019-11-21 17:14 ` Ingo Molnar
2019-11-21 17:35 ` Peter Zijlstra
2019-11-21 17:12 ` Ingo Molnar
2019-11-21 17:34 ` Luck, Tony
2019-11-22 10:51 ` Peter Zijlstra
2019-11-22 15:27 ` Peter Zijlstra
2019-11-22 17:22 ` Luck, Tony
2019-11-22 20:23 ` Peter Zijlstra
2019-11-22 18:02 ` Luck, Tony
2019-11-22 20:23 ` Peter Zijlstra
2019-11-22 20:42 ` Fenghua Yu
2019-11-22 21:25 ` Andy Lutomirski
2019-12-12 8:57 ` Peter Zijlstra
2019-12-12 18:52 ` Luck, Tony
2019-12-12 19:46 ` Luck, Tony
2019-12-12 20:01 ` Andy Lutomirski
2019-12-16 16:21 ` David Laight
2019-11-22 18:44 ` Sean Christopherson
2019-11-22 20:30 ` Peter Zijlstra
2019-11-23 0:30 ` Luck, Tony
2019-11-25 16:13 ` Sean Christopherson
2019-12-02 18:20 ` Luck, Tony
2019-12-12 8:59 ` Peter Zijlstra
2020-01-10 19:24 ` [PATCH v11] x86/split_lock: Enable split lock detection by kernel Luck, Tony
2020-01-14 5:55 ` Sean Christopherson
2020-01-15 22:27 ` Luck, Tony
2020-01-15 22:57 ` Sean Christopherson
2020-01-15 23:48 ` Luck, Tony
2020-01-22 18:55 ` [PATCH v12] " Luck, Tony
2020-01-22 19:04 ` Borislav Petkov
2020-01-22 20:03 ` Luck, Tony
2020-01-22 20:55 ` Borislav Petkov
2020-01-22 22:42 ` Arvind Sankar
2020-01-22 22:52 ` Arvind Sankar
2020-01-22 23:24 ` Luck, Tony
2020-01-23 0:45 ` Arvind Sankar
2020-01-23 1:23 ` Luck, Tony [this message]
2020-01-23 4:21 ` Arvind Sankar
2020-01-23 17:15 ` Luck, Tony
2020-01-23 3:53 ` [PATCH v13] " Luck, Tony
2020-01-23 4:45 ` Arvind Sankar
2020-01-23 23:16 ` [PATCH v14] " Luck, Tony
2020-01-24 21:36 ` Thomas Gleixner
2020-01-25 2:47 ` [PATCH v15] " Luck, Tony
2020-01-25 10:44 ` Borislav Petkov
2020-01-25 19:55 ` Luck, Tony
2020-01-25 20:12 ` Peter Zijlstra
2020-01-25 20:33 ` Borislav Petkov
2020-01-25 21:42 ` Luck, Tony
2020-01-25 22:17 ` Borislav Petkov
2020-01-25 20:29 ` Borislav Petkov
2020-01-25 13:41 ` Thomas Gleixner
2020-01-25 22:07 ` [PATCH v16] " Luck, Tony
2020-01-25 22:43 ` Mark D Rustad
2020-01-25 23:10 ` Luck, Tony
2020-01-26 17:27 ` Mark D Rustad
2020-01-26 20:05 ` [PATCH v17] " Luck, Tony
2020-01-29 12:31 ` Thomas Gleixner
2020-01-29 15:24 ` [tip: x86/cpu] " tip-bot2 for Peter Zijlstra (Intel)
2020-02-03 20:41 ` [PATCH v17] " Sean Christopherson
2020-02-06 0:49 ` [PATCH] x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR Luck, Tony
2020-02-06 1:18 ` Andy Lutomirski
2020-02-06 16:46 ` Luck, Tony
2020-02-06 19:37 ` Andy Lutomirski
2020-03-03 19:22 ` Sean Christopherson
2020-02-04 0:04 ` [PATCH v17] x86/split_lock: Enable split lock detection by kernel Sean Christopherson
2020-02-04 12:52 ` Thomas Gleixner
2020-01-26 0:34 ` [PATCH v16] " Andy Lutomirski
2020-01-26 20:01 ` Luck, Tony
2020-01-25 21:25 ` [PATCH v15] " Arvind Sankar
2020-01-25 21:50 ` Luck, Tony
2020-01-25 23:51 ` Arvind Sankar
2020-01-26 2:52 ` Luck, Tony
2020-01-27 2:05 ` Tony Luck
2020-01-27 8:04 ` Peter Zijlstra
2020-01-27 8:36 ` Peter Zijlstra
2020-01-27 17:35 ` Luck, Tony
2020-01-27 8:02 ` Peter Zijlstra
2019-12-13 0:09 ` [PATCH v11] x86/split_lock: Enable split lock detection by kernel parameter Tony Luck
2019-12-13 0:16 ` Luck, Tony
2019-11-21 17:43 ` [PATCH v10 6/6] " David Laight
2019-11-21 17:51 ` Andy Lutomirski
2019-11-21 18:53 ` Fenghua Yu
2019-11-21 19:01 ` Andy Lutomirski
2019-11-21 20:25 ` Fenghua Yu
2019-11-21 20:19 ` Peter Zijlstra
2019-11-21 19:46 ` Peter Zijlstra
2019-11-21 20:25 ` Peter Zijlstra
2019-11-21 21:22 ` Andy Lutomirski
2019-11-22 9:25 ` Peter Zijlstra
2019-11-22 17:48 ` Luck, Tony
2019-11-22 20:31 ` Peter Zijlstra
2019-11-22 21:23 ` Andy Lutomirski
2019-12-11 17:52 ` Peter Zijlstra
2019-12-11 18:12 ` Andy Lutomirski
2019-12-11 22:34 ` Peter Zijlstra
2019-12-12 19:40 ` Andy Lutomirski
2019-12-16 9:59 ` David Laight
2019-12-16 17:22 ` Andy Lutomirski
2019-12-16 17:45 ` David Laight
2019-12-16 18:06 ` Andy Lutomirski
2019-12-17 10:03 ` David Laight
2019-12-11 18:44 ` Luck, Tony
2019-12-11 22:39 ` Peter Zijlstra
2019-12-12 10:36 ` David Laight
2019-12-12 13:04 ` Peter Zijlstra
2019-12-12 16:02 ` Andy Lutomirski
2019-12-12 16:23 ` David Laight
2019-12-12 16:29 ` David Laight
2019-11-21 19:56 ` Peter Zijlstra
2019-11-21 21:01 ` Andy Lutomirski
2019-11-22 9:36 ` Peter Zijlstra
2019-11-22 9:46 ` David Laight
2019-11-22 20:32 ` Peter Zijlstra
2019-11-21 8:00 ` Peter Zijlstra
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