Messages in this thread | | | Date | Fri, 3 Apr 2020 11:01:49 -0700 | From | Sean Christopherson <> | Subject | Re: [PATCH 1/1] x86/split_lock: check split lock feature on initialization |
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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 >
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