[PATCH v5 3/3] KVM/arm/arm64: enable enhanced armv8 fp/simd lazy switch
Mario Smarduch
m.smarduch at samsung.com
Fri Dec 18 17:17:00 PST 2015
On 12/18/2015 5:54 AM, Christoffer Dall wrote:
> On Sun, Dec 06, 2015 at 05:07:14PM -0800, Mario Smarduch wrote:
>> This patch tracks armv7 and armv8 fp/simd hardware state with cptr_el2 register.
>> On vcpu_load for 32 bit guests enable FP access, and enable fp/simd
>> trapping for 32 and 64 bit guests. On first fp/simd access trap to handler
>> to save host and restore guest context, and clear trapping bits to enable vcpu
>> lazy mode. On vcpu_put if trap bits are clear save guest and restore host
>> context and also save 32 bit guest fpexc register.
>>
>> Signed-off-by: Mario Smarduch <m.smarduch at samsung.com>
>> ---
>> arch/arm/include/asm/kvm_emulate.h | 5 ++
>> arch/arm/include/asm/kvm_host.h | 2 +
>> arch/arm/kvm/arm.c | 20 +++++--
>> arch/arm64/include/asm/kvm_asm.h | 2 +
>> arch/arm64/include/asm/kvm_emulate.h | 15 +++--
>> arch/arm64/include/asm/kvm_host.h | 16 +++++-
>> arch/arm64/kernel/asm-offsets.c | 1 +
>> arch/arm64/kvm/Makefile | 3 +-
>> arch/arm64/kvm/fpsimd_switch.S | 38 ++++++++++++
>> arch/arm64/kvm/hyp.S | 108 +++++++++++++----------------------
>> arch/arm64/kvm/hyp_head.S | 48 ++++++++++++++++
>> 11 files changed, 181 insertions(+), 77 deletions(-)
>> create mode 100644 arch/arm64/kvm/fpsimd_switch.S
>> create mode 100644 arch/arm64/kvm/hyp_head.S
>>
>> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
>> index 3de11a2..13feed5 100644
>> --- a/arch/arm/include/asm/kvm_emulate.h
>> +++ b/arch/arm/include/asm/kvm_emulate.h
>> @@ -243,6 +243,11 @@ static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
>> }
>> }
>>
>> +static inline bool kvm_guest_vcpu_is_32bit(struct kvm_vcpu *vcpu)
>> +{
>> + return true;
>> +}
>> +
>> #ifdef CONFIG_VFPv3
>> /* Called from vcpu_load - save fpexc and enable guest access to fp/simd unit */
>> static inline void kvm_enable_vcpu_fpexc(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> index ecc883a..720ae51 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -227,6 +227,8 @@ int kvm_perf_teardown(void);
>> void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>>
>> struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>> +
>> +static inline void kvm_save_guest_vcpu_fpexc(struct kvm_vcpu *vcpu) {}
>> void kvm_restore_host_vfp_state(struct kvm_vcpu *);
>>
>> static inline void kvm_arch_hardware_disable(void) {}
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index 1de07ab..dd59f8a 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -292,8 +292,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>>
>> kvm_arm_set_running_vcpu(vcpu);
>>
>> - /* Save and enable FPEXC before we load guest context */
>> - kvm_enable_vcpu_fpexc(vcpu);
>> + /*
>> + * For 32bit guest executing on arm64, enable fp/simd access in
>> + * EL2. On arm32 save host fpexc and then enable fp/simd access.
>> + */
>> + if (kvm_guest_vcpu_is_32bit(vcpu))
>> + kvm_enable_vcpu_fpexc(vcpu);
>>
>> /* reset hyp cptr register to trap on tracing and vfp/simd access*/
>> vcpu_reset_cptr(vcpu);
>> @@ -302,10 +306,18 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>> void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>> {
>> /* If the fp/simd registers are dirty save guest, restore host. */
>> - if (kvm_vcpu_vfp_isdirty(vcpu))
>> + if (kvm_vcpu_vfp_isdirty(vcpu)) {
>> kvm_restore_host_vfp_state(vcpu);
>>
>> - /* Restore host FPEXC trashed in vcpu_load */
>> + /*
>> + * For 32bit guest on arm64 save the guest fpexc register
>> + * in EL2 mode.
>> + */
>> + if (kvm_guest_vcpu_is_32bit(vcpu))
>> + kvm_save_guest_vcpu_fpexc(vcpu);
>> + }
>> +
>> + /* For arm32 restore host FPEXC trashed in vcpu_load. */
>> kvm_restore_host_fpexc(vcpu);
>>
>> /*
>> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
>> index 5e37710..d53d069 100644
>> --- a/arch/arm64/include/asm/kvm_asm.h
>> +++ b/arch/arm64/include/asm/kvm_asm.h
>> @@ -117,6 +117,8 @@ extern char __kvm_hyp_vector[];
>> extern void __kvm_flush_vm_context(void);
>> extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
>> extern void __kvm_tlb_flush_vmid(struct kvm *kvm);
>> +extern void __kvm_vcpu_enable_fpexc32(void);
>> +extern void __kvm_vcpu_save_fpexc32(struct kvm_vcpu *vcpu);
>>
>> extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index 8dccbd7..bbbee9d 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -290,13 +290,20 @@ static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
>> return data; /* Leave LE untouched */
>> }
>>
>> -static inline void kvm_enable_vcpu_fpexc(struct kvm_vcpu *vcpu) {}
>> -static inline void kvm_restore_host_fpexc(struct kvm_vcpu *vcpu) {}
>> -static inline void vcpu_reset_cptr(struct kvm_vcpu *vcpu) {}
>> +static inline bool kvm_guest_vcpu_is_32bit(struct kvm_vcpu *vcpu)
>> +{
>> + return !(vcpu->arch.hcr_el2 & HCR_RW);
>> +}
>> +
>> +static inline void vcpu_reset_cptr(struct kvm_vcpu *vcpu)
>> +{
>> + vcpu->arch.cptr_el2 = CPTR_EL2_TTA | CPTR_EL2_TFP;
>> +}
>> +
>>
>> static inline bool kvm_vcpu_vfp_isdirty(struct kvm_vcpu *vcpu)
>> {
>> - return false;
>> + return !!(~vcpu->arch.cptr_el2 & CPTR_EL2_TFP);
>> }
>>
>> #endif /* __ARM64_KVM_EMULATE_H__ */
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index e16fd39..0c65393 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -100,6 +100,7 @@ struct kvm_vcpu_arch {
>> /* HYP configuration */
>> u64 hcr_el2;
>> u32 mdcr_el2;
>> + u32 cptr_el2;
>>
>> /* Exception Information */
>> struct kvm_vcpu_fault_info fault;
>> @@ -248,7 +249,20 @@ static inline void kvm_arch_hardware_unsetup(void) {}
>> static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>> static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
>> static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
>> -static inline void kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu) {}
>> +
>> +static inline void kvm_enable_vcpu_fpexc(struct kvm_vcpu *vcpu)
>> +{
>> + /* Enable FP/SIMD access from EL2 mode*/
>> + kvm_call_hyp(__kvm_vcpu_enable_fpexc32);
>> +}
>> +
>> +static inline void kvm_save_guest_vcpu_fpexc(struct kvm_vcpu *vcpu)
>> +{
>> + /* Save FPEXEC32_EL2 in EL2 mode */
>> + kvm_call_hyp(__kvm_vcpu_save_fpexc32, vcpu);
>> +}
>> +static inline void kvm_restore_host_fpexc(struct kvm_vcpu *vcpu) {}
>> +void kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu);
>>
>> void kvm_arm_init_debug(void);
>> void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>> index 8d89cf8..3c8d836 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -123,6 +123,7 @@ int main(void)
>> DEFINE(DEBUG_WVR, offsetof(struct kvm_guest_debug_arch, dbg_wvr));
>> DEFINE(VCPU_HCR_EL2, offsetof(struct kvm_vcpu, arch.hcr_el2));
>> DEFINE(VCPU_MDCR_EL2, offsetof(struct kvm_vcpu, arch.mdcr_el2));
>> + DEFINE(VCPU_CPTR_EL2, offsetof(struct kvm_vcpu, arch.cptr_el2));
>> DEFINE(VCPU_IRQ_LINES, offsetof(struct kvm_vcpu, arch.irq_lines));
>> DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_context));
>> DEFINE(VCPU_HOST_DEBUG_STATE, offsetof(struct kvm_vcpu, arch.host_debug_state));
>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>> index 1949fe5..262b9a5 100644
>> --- a/arch/arm64/kvm/Makefile
>> +++ b/arch/arm64/kvm/Makefile
>> @@ -17,7 +17,8 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(ARM)/psci.o $(ARM)/perf.o
>>
>> kvm-$(CONFIG_KVM_ARM_HOST) += emulate.o inject_fault.o regmap.o
>> kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
>> -kvm-$(CONFIG_KVM_ARM_HOST) += guest.o debug.o reset.o sys_regs.o sys_regs_generic_v8.o
>> +kvm-$(CONFIG_KVM_ARM_HOST) += guest.o debug.o reset.o sys_regs.o
>> +kvm-$(CONFIG_KVM_ARM_HOST) += sys_regs_generic_v8.o fpsimd_switch.o
>>
>> kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic.o
>> kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic-v2.o
>> diff --git a/arch/arm64/kvm/fpsimd_switch.S b/arch/arm64/kvm/fpsimd_switch.S
>> new file mode 100644
>> index 0000000..5295512
>> --- /dev/null
>> +++ b/arch/arm64/kvm/fpsimd_switch.S
>> @@ -0,0 +1,38 @@
>> +/*
>> + * Copyright (C) 2012,2013 - ARM Ltd
>> + * Author: Marc Zyngier <marc.zyngier at arm.com>
>> + *
>
> Is this copied code or new code?
It's mostly refactored copied code.
>
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/linkage.h>
>> +
>> +#include "hyp_head.S"
>> +
>> + .text
>> +/**
>> + * void kvm_restore_host_vfp_state(struct vcpu *vcpu) -
>> + * This function saves the guest, restores host, called from host.
>> + */
>> +ENTRY(kvm_restore_host_vfp_state)
>> + push xzr, lr
>> +
>> + add x2, x0, #VCPU_CONTEXT
>> + bl __save_fpsimd
>> +
>> + ldr x2, [x0, #VCPU_HOST_CONTEXT]
>> + bl __restore_fpsimd
>> +
>> + pop xzr, lr
>> + ret
>> +ENDPROC(kvm_restore_host_vfp_state)
>> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
>> index e583613..b8b1afb 100644
>> --- a/arch/arm64/kvm/hyp.S
>> +++ b/arch/arm64/kvm/hyp.S
>> @@ -17,23 +17,7 @@
>>
>> #include <linux/linkage.h>
>>
>> -#include <asm/alternative.h>
>> -#include <asm/asm-offsets.h>
>> -#include <asm/assembler.h>
>> -#include <asm/cpufeature.h>
>> -#include <asm/debug-monitors.h>
>> -#include <asm/esr.h>
>> -#include <asm/fpsimdmacros.h>
>> -#include <asm/kvm.h>
>> -#include <asm/kvm_arm.h>
>> -#include <asm/kvm_asm.h>
>> -#include <asm/kvm_mmu.h>
>> -#include <asm/memory.h>
>> -
>> -#define CPU_GP_REG_OFFSET(x) (CPU_GP_REGS + x)
>> -#define CPU_XREG_OFFSET(x) CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)
>> -#define CPU_SPSR_OFFSET(x) CPU_GP_REG_OFFSET(CPU_SPSR + 8*x)
>> -#define CPU_SYSREG_OFFSET(x) (CPU_SYSREGS + 8*x)
>> +#include "hyp_head.S"
>>
>> .text
>> .pushsection .hyp.text, "ax"
>> @@ -104,20 +88,6 @@
>> restore_common_regs
>> .endm
>>
>> -.macro save_fpsimd
>> - // x2: cpu context address
>> - // x3, x4: tmp regs
>> - add x3, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
>> - fpsimd_save x3, 4
>> -.endm
>> -
>> -.macro restore_fpsimd
>> - // x2: cpu context address
>> - // x3, x4: tmp regs
>> - add x3, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
>> - fpsimd_restore x3, 4
>> -.endm
>> -
>> .macro save_guest_regs
>> // x0 is the vcpu address
>> // x1 is the return code, do not corrupt!
>> @@ -385,14 +355,6 @@
>> tbz \tmp, #KVM_ARM64_DEBUG_DIRTY_SHIFT, \target
>> .endm
>>
>> -/*
>> - * Branch to target if CPTR_EL2.TFP bit is set (VFP/SIMD trapping enabled)
>> - */
>> -.macro skip_fpsimd_state tmp, target
>> - mrs \tmp, cptr_el2
>> - tbnz \tmp, #CPTR_EL2_TFP_SHIFT, \target
>> -.endm
>> -
>> .macro compute_debug_state target
>> // Compute debug state: If any of KDE, MDE or KVM_ARM64_DEBUG_DIRTY
>> // is set, we do a full save/restore cycle and disable trapping.
>> @@ -433,10 +395,6 @@
>> mrs x5, ifsr32_el2
>> stp x4, x5, [x3]
>>
>> - skip_fpsimd_state x8, 2f
>> - mrs x6, fpexc32_el2
>> - str x6, [x3, #16]
>> -2:
>> skip_debug_state x8, 1f
>> mrs x7, dbgvcr32_el2
>> str x7, [x3, #24]
>> @@ -467,22 +425,9 @@
>>
>> .macro activate_traps
>> ldr x2, [x0, #VCPU_HCR_EL2]
>> -
>> - /*
>> - * We are about to set CPTR_EL2.TFP to trap all floating point
>> - * register accesses to EL2, however, the ARM ARM clearly states that
>> - * traps are only taken to EL2 if the operation would not otherwise
>> - * trap to EL1. Therefore, always make sure that for 32-bit guests,
>> - * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
>> - */
>> - tbnz x2, #HCR_RW_SHIFT, 99f // open code skip_32bit_state
>> - mov x3, #(1 << 30)
>> - msr fpexc32_el2, x3
>> - isb
>> -99:
>> msr hcr_el2, x2
>> - mov x2, #CPTR_EL2_TTA
>> - orr x2, x2, #CPTR_EL2_TFP
>> +
>> + ldr w2, [x0, VCPU_CPTR_EL2]
>> msr cptr_el2, x2
>>
>> mov x2, #(1 << 15) // Trap CP15 Cr=15
>> @@ -668,15 +613,15 @@ __restore_debug:
>>
>> ret
>>
>> -__save_fpsimd:
>> - skip_fpsimd_state x3, 1f
>> +ENTRY(__save_fpsimd)
>> save_fpsimd
>> -1: ret
>> + ret
>> +ENDPROC(__save_fpsimd)
>>
>> -__restore_fpsimd:
>> - skip_fpsimd_state x3, 1f
>> +ENTRY(__restore_fpsimd)
>> restore_fpsimd
>> -1: ret
>> + ret
>> +ENDPROC(__restore_fpsimd)
>>
>> switch_to_guest_fpsimd:
>> push x4, lr
>> @@ -763,7 +708,6 @@ __kvm_vcpu_return:
>> add x2, x0, #VCPU_CONTEXT
>>
>> save_guest_regs
>> - bl __save_fpsimd
>> bl __save_sysregs
>>
>> skip_debug_state x3, 1f
>> @@ -784,8 +728,10 @@ __kvm_vcpu_return:
>> kern_hyp_va x2
>>
>> bl __restore_sysregs
>> - bl __restore_fpsimd
>> - /* Clear FPSIMD and Trace trapping */
>> +
>> + /* Save CPTR_EL2 between exits and clear FPSIMD and Trace trapping */
>> + mrs x3, cptr_el2
>> + str w3, [x0, VCPU_CPTR_EL2]
>> msr cptr_el2, xzr
>>
>> skip_debug_state x3, 1f
>> @@ -863,6 +809,34 @@ ENTRY(__kvm_flush_vm_context)
>> ret
>> ENDPROC(__kvm_flush_vm_context)
>>
>> +/**
>> + * void __kvm_enable_fpexc32(void) -
>> + * We may be entering the guest and set CPTR_EL2.TFP to trap all floating
>> + * point register accesses to EL2, however, the ARM manual clearly states
>> + * that traps are only taken to EL2 if the operation would not otherwise
>> + * trap to EL1. Therefore, always make sure that for 32-bit guests,
>> + * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
>> + */
>> +ENTRY(__kvm_vcpu_enable_fpexc32)
>> + mov x3, #(1 << 30)
>> + msr fpexc32_el2, x3
>> + isb
>
> this is only called via a hypercall so do you really need the ISB?
Same comment as in 2nd patch for the isb.
>
>> + ret
>> +ENDPROC(__kvm_vcpu_enable_fpexc32)
>> +
>> +/**
>> + * void __kvm_save_fpexc32(void) -
>> + * This function restores guest FPEXC to its vcpu context, we call this
>> + * function from vcpu_put.
>> + */
>> +ENTRY(__kvm_vcpu_save_fpexc32)
>> + kern_hyp_va x0
>> + add x2, x0, #VCPU_CONTEXT
>> + mrs x1, fpexc32_el2
>> + str x1, [x2, #CPU_SYSREG_OFFSET(FPEXC32_EL2)]
>> + ret
>> +ENDPROC(__kvm_vcpu_save_fpexc32)
>> +
>> __kvm_hyp_panic:
>> // Guess the context by looking at VTTBR:
>> // If zero, then we're already a host.
>> diff --git a/arch/arm64/kvm/hyp_head.S b/arch/arm64/kvm/hyp_head.S
>> new file mode 100644
>> index 0000000..bb32824
>> --- /dev/null
>> +++ b/arch/arm64/kvm/hyp_head.S
>> @@ -0,0 +1,48 @@
>> +/*
>> + * Copyright (C) 2012,2013 - ARM Ltd
>> + * Author: Marc Zyngier <marc.zyngier at arm.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <asm/alternative.h>
>> +#include <asm/asm-offsets.h>
>> +#include <asm/assembler.h>
>> +#include <asm/cpufeature.h>
>> +#include <asm/debug-monitors.h>
>> +#include <asm/esr.h>
>> +#include <asm/fpsimdmacros.h>
>> +#include <asm/kvm.h>
>> +#include <asm/kvm_arm.h>
>> +#include <asm/kvm_asm.h>
>> +#include <asm/kvm_mmu.h>
>> +#include <asm/memory.h>
>> +
>> +#define CPU_GP_REG_OFFSET(x) (CPU_GP_REGS + x)
>> +#define CPU_XREG_OFFSET(x) CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)
>> +#define CPU_SPSR_OFFSET(x) CPU_GP_REG_OFFSET(CPU_SPSR + 8*x)
>> +#define CPU_SYSREG_OFFSET(x) (CPU_SYSREGS + 8*x)
>> +
>> +.macro save_fpsimd
>> + // x2: cpu context address
>> + // x3, x4: tmp regs
>> + add x3, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
>> + fpsimd_save x3, 4
>> +.endm
>> +
>> +.macro restore_fpsimd
>> + // x2: cpu context address
>> + // x3, x4: tmp regs
>> + add x3, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
>> + fpsimd_restore x3, 4
>> +.endm
>> --
>> 1.9.1
>>
>
> I'm not going to review the details of this, since we have to rebase it
> on the world-switch in C, sorry.
That fine.
>
> The good news is that it should be much simpler to write in C-code.
>
> Let me know if you don't have the bandwidth to rebase this, in that case
> I'll be happy to help.
Let me see where I'm at by the end of Monday, if there is a rush to get it into
next release by all means.
>
> Thanks,
> -Christoffer
>
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