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    SubjectRe: [PATCH v3 4/8] x86/split_lock: Add and export split_lock_detect_enabled() and split_lock_detect_fatal()
    On Thu, Feb 06, 2020 at 03:04:08PM +0800, Xiaoyao Li wrote:
    > These two functions will be used by KVM to check whether host's
    > sld_state.
    >
    > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
    > ---
    > arch/x86/include/asm/cpu.h | 4 ++++
    > arch/x86/kernel/cpu/intel.c | 12 ++++++++++++
    > 2 files changed, 16 insertions(+)
    >
    > diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
    > index 2b20829db450..f5172dbd3f01 100644
    > --- a/arch/x86/include/asm/cpu.h
    > +++ b/arch/x86/include/asm/cpu.h
    > @@ -46,6 +46,8 @@ unsigned int x86_stepping(unsigned int sig);
    > extern void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c);
    > extern void switch_to_sld(unsigned long tifn);
    > extern bool handle_user_split_lock(unsigned long ip);
    > +extern bool split_lock_detect_enabled(void);
    > +extern bool split_lock_detect_fatal(void);
    > #else
    > static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {}
    > static inline void switch_to_sld(unsigned long tifn) {}
    > @@ -53,5 +55,7 @@ static inline bool handle_user_split_lock(unsigned long ip)
    > {
    > return false;
    > }
    > +static inline bool split_lock_detect_enabled(void) { return false; }
    > +static inline bool split_lock_detect_fatal(void) { return false; }
    > #endif
    > #endif /* _ASM_X86_CPU_H */
    > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
    > index ff27d026cb4a..b67b46ea66df 100644
    > --- a/arch/x86/kernel/cpu/intel.c
    > +++ b/arch/x86/kernel/cpu/intel.c
    > @@ -1131,3 +1131,15 @@ void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c)
    > if (ia32_core_caps & MSR_IA32_CORE_CAPS_SPLIT_LOCK_DETECT)
    > split_lock_setup();
    > }
    > +
    > +bool split_lock_detect_enabled(void)
    > +{
    > + return sld_state != sld_off;
    > +}
    > +EXPORT_SYMBOL_GPL(split_lock_detect_enabled);

    Hmm, ideally this would be static inline. Patch 8 (to expose SLD to the
    guest) queries this in vmx_vcpu_run(), I'd prefer to avoid the extra
    CALL+RET in that path.

    > +bool split_lock_detect_fatal(void)
    > +{
    > + return sld_state == sld_fatal;
    > +}
    > +EXPORT_SYMBOL_GPL(split_lock_detect_fatal);

    split_lock_detect_fatal() isn't used in this series, it shouldn't be added.

    > --
    > 2.23.0
    >

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