From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Benjamin Lamowski <benjamin.lamowski@kernkonzept.com>
Cc: xiaoyao.li@intel.com, philipp.eppelt@kernkonzept.com,
bp@alien8.de, fenghua.yu@intel.com, hpa@zytor.com,
linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com,
nivedita@alum.mit.edu, pbonzini@redhat.com, peterz@infradead.org,
tglx@linutronix.de, tony.luck@intel.com, x86@kernel.org
Subject: Re: [PATCH 1/1] x86/split_lock: check split lock feature on initialization
Date: Fri, 3 Apr 2020 11:01:49 -0700 [thread overview]
Message-ID: <20200403180149.GH2701@linux.intel.com> (raw)
In-Reply-To: <20200403174403.306363-2-benjamin.lamowski@kernkonzept.com>
On Fri, Apr 03, 2020 at 07:44:03PM +0200, Benjamin Lamowski wrote:
> While the setup code probes for the availability of the TEST_CTRL MSR,
> the current initialization code unconditionally probes it even on
> systems where this architectural MSR is not available.
>
> This commit changes the code to check for the availability of the split
> lock detect feature before initializing it.
>
> Fixes: dbaba47085b0c ("x86/split_lock: Rework the initialization flow of split lock detection")
> Signed-off-by: Benjamin Lamowski <benjamin.lamowski@kernkonzept.com>
> ---
> arch/x86/kernel/cpu/intel.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index 9a26e972cdea..70d338ff4807 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -586,7 +586,7 @@ static void init_intel_misc_features(struct cpuinfo_x86 *c)
> wrmsrl(MSR_MISC_FEATURES_ENABLES, msr);
> }
>
> -static void split_lock_init(void);
> +static void split_lock_init(struct cpuinfo_x86 *c);
>
> static void init_intel(struct cpuinfo_x86 *c)
> {
> @@ -703,7 +703,7 @@ static void init_intel(struct cpuinfo_x86 *c)
> if (tsx_ctrl_state == TSX_CTRL_DISABLE)
> tsx_disable();
>
> - split_lock_init();
> + split_lock_init(c);
> }
>
> #ifdef CONFIG_X86_32
> @@ -1061,9 +1061,10 @@ static void sld_update_msr(bool on)
> wrmsrl(MSR_TEST_CTRL, test_ctrl_val);
> }
>
> -static void split_lock_init(void)
> +static void split_lock_init(struct cpuinfo_x86 *c)
> {
> - split_lock_verify_msr(sld_state != sld_off);
> + if (cpu_has(c, X86_FEATURE_SPLIT_LOCK_DETECT))
> + split_lock_verify_msr(sld_state != sld_off);
Calling split_lock_verify_msr() with X86_FEATURE_SPLIT_LOCK_DETECT=0 is
intentional, the idea is to ensure SLD is disabled on all CPUs, e.g. in the
unlikely scenario that BIOS enabled SLD.
The first rdmsrl_safe() should short circuit split_lock_verify_msr() if
the RDMSR faults, i.e. it might fault, but it shouldn't WARN. Are you
seeing issues or was this found via code inspection?
> }
>
> bool handle_user_split_lock(struct pt_regs *regs, long error_code)
> --
> 2.25.1
>
next prev parent reply other threads:[~2020-04-03 18:01 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
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 [this message]
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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