1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers 4 * 5 * Copyright 2018 Arm Limited 6 * Author: Dave Martin <Dave.Martin@arm.com> 7 */ 8 #include <linux/irqflags.h> 9 #include <linux/sched.h> 10 #include <linux/thread_info.h> 11 #include <linux/kvm_host.h> 12 #include <asm/fpsimd.h> 13 #include <asm/kvm_asm.h> 14 #include <asm/kvm_mmu.h> 15 #include <asm/sysreg.h> 16 17 /* 18 * Called on entry to KVM_RUN unless this vcpu previously ran at least 19 * once and the most recent prior KVM_RUN for this vcpu was called from 20 * the same task as current (highly likely). 21 * 22 * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu), 23 * such that on entering hyp the relevant parts of current are already 24 * mapped. 25 */ 26 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu) 27 { 28 int ret; 29 30 struct thread_info *ti = ¤t->thread_info; 31 struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state; 32 33 /* 34 * Make sure the host task thread flags and fpsimd state are 35 * visible to hyp: 36 */ 37 ret = create_hyp_mappings(ti, ti + 1, PAGE_HYP); 38 if (ret) 39 goto error; 40 41 ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP); 42 if (ret) 43 goto error; 44 45 vcpu->arch.host_thread_info = kern_hyp_va(ti); 46 vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd); 47 error: 48 return ret; 49 } 50 51 /* 52 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's. 53 * The actual loading is done by the FPSIMD access trap taken to hyp. 54 * 55 * Here, we just set the correct metadata to indicate that the FPSIMD 56 * state in the cpu regs (if any) belongs to current on the host. 57 * 58 * TIF_SVE is backed up here, since it may get clobbered with guest state. 59 * This flag is restored by kvm_arch_vcpu_put_fp(vcpu). 60 */ 61 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) 62 { 63 BUG_ON(!current->mm); 64 65 vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED | 66 KVM_ARM64_HOST_SVE_IN_USE | 67 KVM_ARM64_HOST_SVE_ENABLED); 68 vcpu->arch.flags |= KVM_ARM64_FP_HOST; 69 70 if (test_thread_flag(TIF_SVE)) 71 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE; 72 73 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) 74 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED; 75 } 76 77 /* 78 * If the guest FPSIMD state was loaded, update the host's context 79 * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu 80 * so that they will be written back if the kernel clobbers them due to 81 * kernel-mode NEON before re-entry into the guest. 82 */ 83 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) 84 { 85 WARN_ON_ONCE(!irqs_disabled()); 86 87 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { 88 fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.gp_regs.fp_regs, 89 vcpu->arch.sve_state, 90 vcpu->arch.sve_max_vl); 91 92 clear_thread_flag(TIF_FOREIGN_FPSTATE); 93 update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu)); 94 } 95 } 96 97 /* 98 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the 99 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu 100 * disappears and another task or vcpu appears that recycles the same 101 * struct fpsimd_state. 102 */ 103 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) 104 { 105 unsigned long flags; 106 bool host_has_sve = system_supports_sve(); 107 bool guest_has_sve = vcpu_has_sve(vcpu); 108 109 local_irq_save(flags); 110 111 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { 112 u64 *guest_zcr = &vcpu->arch.ctxt.sys_regs[ZCR_EL1]; 113 114 fpsimd_save_and_flush_cpu_state(); 115 116 if (guest_has_sve) 117 *guest_zcr = read_sysreg_s(SYS_ZCR_EL12); 118 } else if (host_has_sve) { 119 /* 120 * The FPSIMD/SVE state in the CPU has not been touched, and we 121 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been 122 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE 123 * for EL0. To avoid spurious traps, restore the trap state 124 * seen by kvm_arch_vcpu_load_fp(): 125 */ 126 if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED) 127 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN); 128 else 129 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0); 130 } 131 132 update_thread_flag(TIF_SVE, 133 vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE); 134 135 local_irq_restore(flags); 136 } 137