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    SubjectRe: [PATCH 2/3] x86/split_lock: Refactor and export handle_user_split_lock() for KVM
    On Thu, Apr 02, 2020 at 07:01:56PM +0200, Thomas Gleixner wrote:
    > Sean Christopherson <sean.j.christopherson@intel.com> writes:
    > > From: Xiaoyao Li <xiaoyao.li@intel.com>
    > >
    > > In the future, KVM will use handle_user_split_lock() to handle #AC
    > > caused by split lock in guest. Due to the fact that KVM doesn't have
    > > a @regs context and will pre-check EFLAGS.AC, move the EFLAGS.AC check
    > > to do_alignment_check().
    > >
    > > Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
    > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
    > > Reviewed-by: Tony Luck <tony.luck@intel.com>
    > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    > > ---
    > > arch/x86/include/asm/cpu.h | 4 ++--
    > > arch/x86/kernel/cpu/intel.c | 7 ++++---
    > > arch/x86/kernel/traps.c | 2 +-
    > > 3 files changed, 7 insertions(+), 6 deletions(-)
    > >
    > > diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
    > > index ff6f3ca649b3..ff567afa6ee1 100644
    > > --- a/arch/x86/include/asm/cpu.h
    > > +++ b/arch/x86/include/asm/cpu.h
    > > @@ -43,11 +43,11 @@ unsigned int x86_stepping(unsigned int sig);
    > > #ifdef CONFIG_CPU_SUP_INTEL
    > > 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(struct pt_regs *regs, long error_code);
    > > +extern bool handle_user_split_lock(unsigned long ip);
    > > #else
    > > static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {}
    > > static inline void switch_to_sld(unsigned long tifn) {}
    > > -static inline bool handle_user_split_lock(struct pt_regs *regs, long error_code)
    > > +static inline bool handle_user_split_lock(unsigned long ip)
    >
    > This is necessary because VMX can be compiled without CPU_SUP_INTEL?

    Ya, it came about when cleaning up the IA32_FEATURE_CONTROL MSR handling
    to consolidate duplicate code.

    config KVM_INTEL
    tristate "KVM for Intel (and compatible) processors support"
    depends on KVM && IA32_FEAT_CTL

    config IA32_FEAT_CTL
    def_bool y
    depends on CPU_SUP_INTEL || CPU_SUP_CENTAUR || CPU_SUP_ZHAOXIN

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