From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
luto@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Arvind Sankar <nivedita@alum.mit.edu>,
Fenghua Yu <fenghua.yu@intel.com>,
Tony Luck <tony.luck@intel.com>
Subject: Re: [PATCH v7 1/2] x86/split_lock: Rework the initialization flow of split lock detection
Date: Mon, 30 Mar 2020 07:26:48 -0700 [thread overview]
Message-ID: <20200330142648.GA24988@linux.intel.com> (raw)
In-Reply-To: <9db4acdc-add6-f63c-fb5c-654cb429b578@intel.com>
On Mon, Mar 30, 2020 at 09:26:25PM +0800, Xiaoyao Li wrote:
> On 3/29/2020 12:32 AM, Sean Christopherson wrote:
> >On Wed, Mar 25, 2020 at 11:09:23AM +0800, Xiaoyao Li wrote:
> >> static void split_lock_init(void)
> >> {
> >>- if (sld_state == sld_off)
> >>- return;
> >>-
> >>- if (__sld_msr_set(true))
> >>- return;
> >>-
> >>- /*
> >>- * If this is anything other than the boot-cpu, you've done
> >>- * funny things and you get to keep whatever pieces.
> >>- */
> >>- pr_warn("MSR fail -- disabled\n");
> >>- sld_state = sld_off;
> >>+ split_lock_verify_msr(sld_state != sld_off);
> >
> >I think it'd be worth a WARN_ON() if this fails with sld_state != off. If
> >the WRMSR fails, then presumably SLD is off when it's expected to be on.
> >The implied WARN on the unsafe WRMSR in sld_update_msr() won't fire unless
> >a task generates an #AC on a non-buggy core and then gets migrated to the
> >buggy core. Even if the WARNs are redundant, if something is wrong it'd be
> >a lot easier for a user to triage/debug if there is a WARN in boot as
> >opposed to a runtime WARN that requires a misbehaving application and
> >scheduler behavior.
> >
>
> IIUC, you're recommending something like below?
>
> WARN_ON(!split_lock_verify_msr(sld_state != sld_off) &&
> sld_state != sld_off);
Ya.
next prev parent reply other threads:[~2020-03-30 14:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 3:09 [PATCH v7 0/2] Fix and optimization of split_lock_detection Xiaoyao Li
2020-03-25 3:09 ` [PATCH v7 1/2] x86/split_lock: Rework the initialization flow of split lock detection Xiaoyao Li
2020-03-28 16:32 ` Sean Christopherson
2020-03-30 13:26 ` Xiaoyao Li
2020-03-30 14:26 ` Sean Christopherson [this message]
2020-03-25 3:09 ` [PATCH v7 2/2] x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR Xiaoyao Li
2020-03-28 16:34 ` Sean Christopherson
2020-03-29 9:13 ` Xiaoyao Li
2020-03-30 18:18 ` Sean Christopherson
2020-04-03 17:44 ` [PATCH 0/1] x86/split_lock: check split lock feature on initialization Benjamin Lamowski
2020-04-03 17:44 ` [PATCH 1/1] " Benjamin Lamowski
2020-04-03 18:01 ` Sean Christopherson
2020-04-06 8:23 ` Benjamin Lamowski
2020-04-06 11:48 ` Xiaoyao Li
2020-04-06 15:57 ` [PATCH v2 0/1] x86/split_lock: check split lock support " Benjamin Lamowski
2020-04-06 16:02 ` [PATCH v2 1/1] " Benjamin Lamowski
2020-04-06 16:17 ` [PATCH v3 " Benjamin Lamowski
2020-04-06 21:24 ` Thomas Gleixner
2020-04-06 21:21 ` [PATCH 0/1] x86/split_lock: check split lock feature " Thomas Gleixner
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