From: Radim Krčmář Date: Fri, 4 Aug 2017 22:12:49 +0000 (+0200) Subject: KVM: x86: generalize guest_cpuid_has_ helpers X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d6321d493319bfd406c484e8359c6101cbda39d3;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git KVM: x86: generalize guest_cpuid_has_ helpers This patch turns guest_cpuid_has_XYZ(cpuid) into guest_cpuid_has(cpuid, X86_FEATURE_XYZ), which gets rid of many very similar helpers. When seeing a X86_FEATURE_*, we can know which cpuid it belongs to, but this information isn't in common code, so we recreate it for KVM. Add some BUILD_BUG_ONs to make sure that it runs nicely. Signed-off-by: Radim Krčmář Reviewed-by: David Hildenbrand Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h index c723d64657d0..4e9ac93b4f3a 100644 --- a/arch/x86/kvm/cpuid.h +++ b/arch/x86/kvm/cpuid.h @@ -3,6 +3,7 @@ #include "x86.h" #include +#include int kvm_update_cpuid(struct kvm_vcpu *vcpu); bool kvm_mpx_supported(void); @@ -29,95 +30,78 @@ static inline int cpuid_maxphyaddr(struct kvm_vcpu *vcpu) return vcpu->arch.maxphyaddr; } -static inline bool guest_cpuid_has_xsave(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; +struct cpuid_reg { + u32 function; + u32 index; + int reg; +}; - if (!static_cpu_has(X86_FEATURE_XSAVE)) - return false; - - best = kvm_find_cpuid_entry(vcpu, 1, 0); - return best && (best->ecx & bit(X86_FEATURE_XSAVE)); -} +static const struct cpuid_reg reverse_cpuid[] = { + [CPUID_1_EDX] = { 1, 0, CPUID_EDX}, + [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX}, + [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX}, + [CPUID_1_ECX] = { 1, 0, CPUID_ECX}, + [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX}, + [CPUID_8000_0001_ECX] = {0xc0000001, 0, CPUID_ECX}, + [CPUID_7_0_EBX] = { 7, 0, CPUID_EBX}, + [CPUID_D_1_EAX] = { 0xd, 1, CPUID_EAX}, + [CPUID_F_0_EDX] = { 0xf, 0, CPUID_EDX}, + [CPUID_F_1_EDX] = { 0xf, 1, CPUID_EDX}, + [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX}, + [CPUID_6_EAX] = { 6, 0, CPUID_EAX}, + [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX}, + [CPUID_7_ECX] = { 7, 0, CPUID_ECX}, + [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX}, +}; -static inline bool guest_cpuid_has_mtrr(struct kvm_vcpu *vcpu) +static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned x86_feature) { - struct kvm_cpuid_entry2 *best; + unsigned x86_leaf = x86_feature / 32; - best = kvm_find_cpuid_entry(vcpu, 1, 0); - return best && (best->edx & bit(X86_FEATURE_MTRR)); -} + BUILD_BUG_ON(!__builtin_constant_p(x86_leaf)); + BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid)); + BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0); -static inline bool guest_cpuid_has_tsc_adjust(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 7, 0); - return best && (best->ebx & bit(X86_FEATURE_TSC_ADJUST)); -} - -static inline bool guest_cpuid_has_smep(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 7, 0); - return best && (best->ebx & bit(X86_FEATURE_SMEP)); + return reverse_cpuid[x86_leaf]; } -static inline bool guest_cpuid_has_smap(struct kvm_vcpu *vcpu) +static __always_inline int *guest_cpuid_get_register(struct kvm_vcpu *vcpu, unsigned x86_feature) { - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 7, 0); - return best && (best->ebx & bit(X86_FEATURE_SMAP)); -} - -static inline bool guest_cpuid_has_fsgsbase(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 7, 0); - return best && (best->ebx & bit(X86_FEATURE_FSGSBASE)); -} - -static inline bool guest_cpuid_has_pku(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 7, 0); - return best && (best->ecx & bit(X86_FEATURE_PKU)); -} - -static inline bool guest_cpuid_has_longmode(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 0x80000001, 0); - return best && (best->edx & bit(X86_FEATURE_LM)); -} + struct kvm_cpuid_entry2 *entry; + const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature); -static inline bool guest_cpuid_has_osvw(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; + entry = kvm_find_cpuid_entry(vcpu, cpuid.function, cpuid.index); + if (!entry) + return NULL; - best = kvm_find_cpuid_entry(vcpu, 0x80000001, 0); - return best && (best->ecx & bit(X86_FEATURE_OSVW)); + switch (cpuid.reg) { + case CPUID_EAX: + return &entry->eax; + case CPUID_EBX: + return &entry->ebx; + case CPUID_ECX: + return &entry->ecx; + case CPUID_EDX: + return &entry->edx; + default: + BUILD_BUG(); + return NULL; + } } -static inline bool guest_cpuid_has_pcid(struct kvm_vcpu *vcpu) +static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu, unsigned x86_feature) { - struct kvm_cpuid_entry2 *best; + int *reg; - best = kvm_find_cpuid_entry(vcpu, 1, 0); - return best && (best->ecx & bit(X86_FEATURE_PCID)); -} + if (x86_feature == X86_FEATURE_XSAVE && + !static_cpu_has(X86_FEATURE_XSAVE)) + return false; -static inline bool guest_cpuid_has_x2apic(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; + reg = guest_cpuid_get_register(vcpu, x86_feature); + if (!reg) + return false; - best = kvm_find_cpuid_entry(vcpu, 1, 0); - return best && (best->ecx & bit(X86_FEATURE_X2APIC)); + return *reg & bit(x86_feature); } static inline bool guest_cpuid_is_amd(struct kvm_vcpu *vcpu) @@ -128,46 +112,6 @@ static inline bool guest_cpuid_is_amd(struct kvm_vcpu *vcpu) return best && best->ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx; } -static inline bool guest_cpuid_has_gbpages(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 0x80000001, 0); - return best && (best->edx & bit(X86_FEATURE_GBPAGES)); -} - -static inline bool guest_cpuid_has_rtm(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 7, 0); - return best && (best->ebx & bit(X86_FEATURE_RTM)); -} - -static inline bool guest_cpuid_has_mpx(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 7, 0); - return best && (best->ebx & bit(X86_FEATURE_MPX)); -} - -static inline bool guest_cpuid_has_rdtscp(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 0x80000001, 0); - return best && (best->edx & bit(X86_FEATURE_RDTSCP)); -} - -static inline bool guest_cpuid_has_nrips(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best; - - best = kvm_find_cpuid_entry(vcpu, 0x8000000a, 0); - return best && (best->edx & bit(X86_FEATURE_NRIPS)); -} - static inline int guest_cpuid_family(struct kvm_vcpu *vcpu) { struct kvm_cpuid_entry2 *best; diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 9b1dd114956a..2fac6f78c420 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4052,7 +4052,8 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu, { __reset_rsvds_bits_mask(vcpu, &context->guest_rsvd_check, cpuid_maxphyaddr(vcpu), context->root_level, - context->nx, guest_cpuid_has_gbpages(vcpu), + context->nx, + guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES), is_pse(vcpu), guest_cpuid_is_amd(vcpu)); } @@ -4114,8 +4115,8 @@ reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context) __reset_rsvds_bits_mask(vcpu, &context->shadow_zero_check, boot_cpu_data.x86_phys_bits, context->shadow_root_level, uses_nx, - guest_cpuid_has_gbpages(vcpu), is_pse(vcpu), - true); + guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES), + is_pse(vcpu), true); } EXPORT_SYMBOL_GPL(reset_shadow_zero_bits_mask); diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c index 0149ac59c273..e9ea2d45ae66 100644 --- a/arch/x86/kvm/mtrr.c +++ b/arch/x86/kvm/mtrr.c @@ -130,7 +130,7 @@ static u8 mtrr_disabled_type(struct kvm_vcpu *vcpu) * enable MTRRs and it is obviously undesirable to run the * guest entirely with UC memory and we use WB. */ - if (guest_cpuid_has_mtrr(vcpu)) + if (guest_cpuid_has(vcpu, X86_FEATURE_MTRR)) return MTRR_TYPE_UNCACHABLE; else return MTRR_TYPE_WRBACK; diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 1107626938cc..b8196aecbdcc 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -5078,7 +5078,7 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu) struct kvm_cpuid_entry2 *entry; /* Update nrips enabled cache */ - svm->nrips_enabled = !!guest_cpuid_has_nrips(&svm->vcpu); + svm->nrips_enabled = !!guest_cpuid_has(&svm->vcpu, X86_FEATURE_NRIPS); if (!kvm_vcpu_apicv_active(vcpu)) return; diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 8e4a2dc85375..96d1f8708cef 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2611,7 +2611,7 @@ static void setup_msrs(struct vcpu_vmx *vmx) if (index >= 0) move_msr_up(vmx, index, save_nmsrs++); index = __find_msr_index(vmx, MSR_TSC_AUX); - if (index >= 0 && guest_cpuid_has_rdtscp(&vmx->vcpu)) + if (index >= 0 && guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDTSCP)) move_msr_up(vmx, index, save_nmsrs++); /* * MSR_STAR is only needed on long mode guests, and only @@ -2671,12 +2671,6 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) } } -static bool guest_cpuid_has_vmx(struct kvm_vcpu *vcpu) -{ - struct kvm_cpuid_entry2 *best = kvm_find_cpuid_entry(vcpu, 1, 0); - return best && (best->ecx & (1 << (X86_FEATURE_VMX & 31))); -} - /* * nested_vmx_allowed() checks whether a guest should be allowed to use VMX * instructions and MSRs (i.e., nested VMX). Nested VMX is disabled for @@ -2685,7 +2679,7 @@ static bool guest_cpuid_has_vmx(struct kvm_vcpu *vcpu) */ static inline bool nested_vmx_allowed(struct kvm_vcpu *vcpu) { - return nested && guest_cpuid_has_vmx(vcpu); + return nested && guest_cpuid_has(vcpu, X86_FEATURE_VMX); } /* @@ -3281,7 +3275,8 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_IA32_BNDCFGS: if (!kvm_mpx_supported() || - (!msr_info->host_initiated && !guest_cpuid_has_mpx(vcpu))) + (!msr_info->host_initiated && + !guest_cpuid_has(vcpu, X86_FEATURE_MPX))) return 1; msr_info->data = vmcs_read64(GUEST_BNDCFGS); break; @@ -3305,7 +3300,8 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) msr_info->data = vcpu->arch.ia32_xss; break; case MSR_TSC_AUX: - if (!guest_cpuid_has_rdtscp(vcpu) && !msr_info->host_initiated) + if (!msr_info->host_initiated && + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP)) return 1; /* Otherwise falls through */ default: @@ -3364,7 +3360,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_IA32_BNDCFGS: if (!kvm_mpx_supported() || - (!msr_info->host_initiated && !guest_cpuid_has_mpx(vcpu))) + (!msr_info->host_initiated && + !guest_cpuid_has(vcpu, X86_FEATURE_MPX))) return 1; if (is_noncanonical_address(data & PAGE_MASK) || (data & MSR_IA32_BNDCFGS_RSVD)) @@ -3427,7 +3424,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) clear_atomic_switch_msr(vmx, MSR_IA32_XSS); break; case MSR_TSC_AUX: - if (!guest_cpuid_has_rdtscp(vcpu) && !msr_info->host_initiated) + if (!msr_info->host_initiated && + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP)) return 1; /* Check reserved bit, higher 32 bits should be zero */ if ((data >> 32) != 0) @@ -9622,7 +9620,7 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu) u32 secondary_exec_ctl = vmx_secondary_exec_control(vmx); if (vmx_rdtscp_supported()) { - bool rdtscp_enabled = guest_cpuid_has_rdtscp(vcpu); + bool rdtscp_enabled = guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP); if (!rdtscp_enabled) secondary_exec_ctl &= ~SECONDARY_EXEC_RDTSCP; @@ -9641,7 +9639,7 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu) struct kvm_cpuid_entry2 *best = kvm_find_cpuid_entry(vcpu, 0x7, 0); bool invpcid_enabled = best && best->ebx & bit(X86_FEATURE_INVPCID) && - guest_cpuid_has_pcid(vcpu); + guest_cpuid_has(vcpu, X86_FEATURE_PCID); if (!invpcid_enabled) { secondary_exec_ctl &= ~SECONDARY_EXEC_ENABLE_INVPCID; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 72d82ab1ee22..ee4e251c82fc 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -310,8 +310,8 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info) (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE); u64 new_state = msr_info->data & (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE); - u64 reserved_bits = ((~0ULL) << cpuid_maxphyaddr(vcpu)) | - 0x2ff | (guest_cpuid_has_x2apic(vcpu) ? 0 : X2APIC_ENABLE); + u64 reserved_bits = ((~0ULL) << cpuid_maxphyaddr(vcpu)) | 0x2ff | + (guest_cpuid_has(vcpu, X86_FEATURE_X2APIC) ? 0 : X2APIC_ENABLE); if (!msr_info->host_initiated && ((msr_info->data & reserved_bits) != 0 || @@ -754,19 +754,19 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) if (cr4 & CR4_RESERVED_BITS) return 1; - if (!guest_cpuid_has_xsave(vcpu) && (cr4 & X86_CR4_OSXSAVE)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && (cr4 & X86_CR4_OSXSAVE)) return 1; - if (!guest_cpuid_has_smep(vcpu) && (cr4 & X86_CR4_SMEP)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_SMEP) && (cr4 & X86_CR4_SMEP)) return 1; - if (!guest_cpuid_has_smap(vcpu) && (cr4 & X86_CR4_SMAP)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_SMAP) && (cr4 & X86_CR4_SMAP)) return 1; - if (!guest_cpuid_has_fsgsbase(vcpu) && (cr4 & X86_CR4_FSGSBASE)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_FSGSBASE) && (cr4 & X86_CR4_FSGSBASE)) return 1; - if (!guest_cpuid_has_pku(vcpu) && (cr4 & X86_CR4_PKE)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_PKU) && (cr4 & X86_CR4_PKE)) return 1; if (is_long_mode(vcpu)) { @@ -779,7 +779,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) return 1; if ((cr4 & X86_CR4_PCIDE) && !(old_cr4 & X86_CR4_PCIDE)) { - if (!guest_cpuid_has_pcid(vcpu)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_PCID)) return 1; /* PCID can not be enabled when cr3[11:0]!=000H or EFER.LMA=0 */ @@ -883,7 +883,7 @@ static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu) { u64 fixed = DR6_FIXED_1; - if (!guest_cpuid_has_rtm(vcpu)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_RTM)) fixed |= DR6_RTM; return fixed; } @@ -1534,8 +1534,9 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr) vcpu->arch.this_tsc_nsec = kvm->arch.cur_tsc_nsec; vcpu->arch.this_tsc_write = kvm->arch.cur_tsc_write; - if (guest_cpuid_has_tsc_adjust(vcpu) && !msr->host_initiated) + if (!msr->host_initiated && guest_cpuid_has(vcpu, X86_FEATURE_TSC_ADJUST)) update_ia32_tsc_adjust_msr(vcpu, offset); + kvm_vcpu_write_tsc_offset(vcpu, offset); raw_spin_unlock_irqrestore(&kvm->arch.tsc_write_lock, flags); @@ -2185,7 +2186,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) kvm_set_lapic_tscdeadline_msr(vcpu, data); break; case MSR_IA32_TSC_ADJUST: - if (guest_cpuid_has_tsc_adjust(vcpu)) { + if (guest_cpuid_has(vcpu, X86_FEATURE_TSC_ADJUST)) { if (!msr_info->host_initiated) { s64 adj = data - vcpu->arch.ia32_tsc_adjust_msr; adjust_tsc_offset_guest(vcpu, adj); @@ -2307,12 +2308,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) vcpu_unimpl(vcpu, "ignored wrmsr: 0x%x data 0x%llx\n", msr, data); break; case MSR_AMD64_OSVW_ID_LENGTH: - if (!guest_cpuid_has_osvw(vcpu)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_OSVW)) return 1; vcpu->arch.osvw.length = data; break; case MSR_AMD64_OSVW_STATUS: - if (!guest_cpuid_has_osvw(vcpu)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_OSVW)) return 1; vcpu->arch.osvw.status = data; break; @@ -2537,12 +2538,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) msr_info->data = 0xbe702111; break; case MSR_AMD64_OSVW_ID_LENGTH: - if (!guest_cpuid_has_osvw(vcpu)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_OSVW)) return 1; msr_info->data = vcpu->arch.osvw.length; break; case MSR_AMD64_OSVW_STATUS: - if (!guest_cpuid_has_osvw(vcpu)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_OSVW)) return 1; msr_info->data = vcpu->arch.osvw.status; break; @@ -6606,7 +6607,7 @@ static void enter_smm(struct kvm_vcpu *vcpu) trace_kvm_enter_smm(vcpu->vcpu_id, vcpu->arch.smbase, true); vcpu->arch.hflags |= HF_SMM_MASK; memset(buf, 0, 512); - if (guest_cpuid_has_longmode(vcpu)) + if (guest_cpuid_has(vcpu, X86_FEATURE_LM)) enter_smm_save_state_64(vcpu, buf); else enter_smm_save_state_32(vcpu, buf); @@ -6658,7 +6659,7 @@ static void enter_smm(struct kvm_vcpu *vcpu) kvm_set_segment(vcpu, &ds, VCPU_SREG_GS); kvm_set_segment(vcpu, &ds, VCPU_SREG_SS); - if (guest_cpuid_has_longmode(vcpu)) + if (guest_cpuid_has(vcpu, X86_FEATURE_LM)) kvm_x86_ops->set_efer(vcpu, 0); kvm_update_cpuid(vcpu); @@ -7424,7 +7425,8 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, int pending_vec, max_bits, idx; struct desc_ptr dt; - if (!guest_cpuid_has_xsave(vcpu) && (sregs->cr4 & X86_CR4_OSXSAVE)) + if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && + (sregs->cr4 & X86_CR4_OSXSAVE)) return -EINVAL; dt.size = sregs->idt.limit;