Messages in this thread | | | Subject | Re: [PATCH 2/3] x86/split_lock: Refactor and export handle_user_split_lock() for KVM | From | Xiaoyao Li <> | Date | Fri, 10 Apr 2020 12:39:03 +0800 |
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On 4/3/2020 3:06 AM, Thomas Gleixner wrote: > Sean Christopherson <sean.j.christopherson@intel.com> writes: >> On Thu, Apr 02, 2020 at 07:01:56PM +0200, Thomas Gleixner wrote: >>>> 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 > > Ah, indeed. So something like the below would make sense. Hmm? > > Of course that can be mangled into Xiaoyao's patches, I'm not worried > about my patch count :) >
I don't mind using yours in my next version.
Hi Paolo,
Are you OK with the kvm part below?
If no objection, I can spin the next version using tglx's.
> > 8<---------------- > --- a/arch/x86/include/asm/cpu.h > +++ b/arch/x86/include/asm/cpu.h > @@ -43,14 +43,14 @@ unsigned int x86_stepping(unsigned int s > #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 int handle_ac_split_lock(unsigned long ip); > extern void split_lock_validate_module_text(struct module *me, void *text, void *text_end); > #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 int handle_ac_split_lock(unsigned long ip) > { > - return false; > + return -ENOSYS; > } > static inline void split_lock_validate_module_text(struct module *me, void *text, void *text_end) {} > #endif > > --- a/arch/x86/kernel/cpu/intel.c > +++ b/arch/x86/kernel/cpu/intel.c > @@ -1102,13 +1102,20 @@ static void split_lock_init(void) > split_lock_verify_msr(sld_state != sld_off); > } > > -bool handle_user_split_lock(struct pt_regs *regs, long error_code) > +int handle_ac_split_lock(unsigned long ip) > { > - if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) > - return false; > + switch (sld_state) { > + case sld_warn: > + break; > + case sld_off: > + pr_warn_once("#AC: Spurious trap at address: 0x%lx\n", ip); > + return -ENOSYS; > + case sld_fatal: > + return -EFAULT; > + } > > pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n", > - current->comm, current->pid, regs->ip); > + current->comm, current->pid, ip); > > /* > * Disable the split lock detection for this task so it can make > @@ -1117,8 +1124,9 @@ bool handle_user_split_lock(struct pt_re > */ > sld_update_msr(false); > set_tsk_thread_flag(current, TIF_SLD); > - return true; > + return 0; > } > +EXPORT_SYMBOL_GPL(handle_ac_split_lock); > > /* > * This function is called only when switching between tasks with > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -304,7 +304,7 @@ dotraplinkage void do_alignment_check(st > > local_irq_enable(); > > - if (handle_user_split_lock(regs, error_code)) > + if (!(regs->flags & X86_EFLAGS_AC) && !handle_ac_split_lock(regs->ip)) > return; > > do_trap(X86_TRAP_AC, SIGBUS, "alignment check", regs, > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -65,6 +65,7 @@ > > MODULE_AUTHOR("Qumranet"); > MODULE_LICENSE("GPL"); > +MODULE_INFO(sld_safe, "Y"); > > #ifdef MODULE > static const struct x86_cpu_id vmx_cpu_id[] = { > @@ -4623,6 +4624,22 @@ static int handle_machine_check(struct k > return 1; > } > > +static bool guest_handles_ac(struct kvm_vcpu *vcpu) > +{ > + /* > + * If guest has alignment checking enabled in CR0 and activated in > + * eflags, then the #AC originated from CPL3 and the guest is able > + * to handle it. It does not matter whether this is a regular or > + * a split lock operation induced #AC. > + */ > + if (vmx_get_cpl(vcpu) == 3 && kvm_read_cr0_bits(vcpu, X86_CR0_AM) && > + kvm_get_rflags(vcpu) & X86_EFLAGS_AC) > + return true; > + > + /* Add guest SLD handling checks here once it's supported */ > + return false; > +} > + > static int handle_exception_nmi(struct kvm_vcpu *vcpu) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > @@ -4630,6 +4647,7 @@ static int handle_exception_nmi(struct k > u32 intr_info, ex_no, error_code; > unsigned long cr2, rip, dr6; > u32 vect_info; > + int err; > > vect_info = vmx->idt_vectoring_info; > intr_info = vmx->exit_intr_info; > @@ -4688,9 +4706,6 @@ static int handle_exception_nmi(struct k > return handle_rmode_exception(vcpu, ex_no, error_code); > > switch (ex_no) { > - case AC_VECTOR: > - kvm_queue_exception_e(vcpu, AC_VECTOR, error_code); > - return 1; > case DB_VECTOR: > dr6 = vmcs_readl(EXIT_QUALIFICATION); > if (!(vcpu->guest_debug & > @@ -4719,6 +4734,29 @@ static int handle_exception_nmi(struct k > kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip; > kvm_run->debug.arch.exception = ex_no; > break; > + case AC_VECTOR: > + if (guest_handles_ac(vcpu)) { > + kvm_queue_exception_e(vcpu, AC_VECTOR, error_code); > + return 1; > + } > + /* > + * Handle #AC caused by split lock detection. If the host > + * mode is sld_warn, then it warns, marks current with > + * TIF_SLD and disables split lock detection. So the guest > + * can just continue. > + * > + * If the host mode is fatal, the handling code warned. Let > + * qemu kill itself. > + * > + * If the host mode is off, then this #AC is bonkers and > + * something is badly wrong. Let it fail as well. > + */ > + err = handle_ac_split_lock(kvm_rip_read(vcpu)); > + if (!err) > + return 1; > + /* Propagate the error type to user space */ > + error_code = err == -EFAULT ? 0x100 : 0x200; > + fallthrough; > default: > kvm_run->exit_reason = KVM_EXIT_EXCEPTION; > kvm_run->ex.exception = ex_no; >
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