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_host.h> 15 #include <asm/kvm_mmu.h> 16 #include <asm/sysreg.h> 17 18 /* 19 * Called on entry to KVM_RUN unless this vcpu previously ran at least 20 * once and the most recent prior KVM_RUN for this vcpu was called from 21 * the same task as current (highly likely). 22 * 23 * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu), 24 * such that on entering hyp the relevant parts of current are already 25 * mapped. 26 */ 27 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu) 28 { 29 int ret; 30 31 struct thread_info *ti = ¤t->thread_info; 32 struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state; 33 34 /* 35 * Make sure the host task thread flags and fpsimd state are 36 * visible to hyp: 37 */ 38 ret = create_hyp_mappings(ti, ti + 1, PAGE_HYP); 39 if (ret) 40 goto error; 41 42 ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP); 43 if (ret) 44 goto error; 45 46 vcpu->arch.host_thread_info = kern_hyp_va(ti); 47 vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd); 48 error: 49 return ret; 50 } 51 52 /* 53 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's. 54 * The actual loading is done by the FPSIMD access trap taken to hyp. 55 * 56 * Here, we just set the correct metadata to indicate that the FPSIMD 57 * state in the cpu regs (if any) belongs to current on the host. 58 * 59 * TIF_SVE is backed up here, since it may get clobbered with guest state. 60 * This flag is restored by kvm_arch_vcpu_put_fp(vcpu). 61 */ 62 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) 63 { 64 BUG_ON(!current->mm); 65 66 vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED | 67 KVM_ARM64_HOST_SVE_IN_USE | 68 KVM_ARM64_HOST_SVE_ENABLED); 69 vcpu->arch.flags |= KVM_ARM64_FP_HOST; 70 71 if (test_thread_flag(TIF_SVE)) 72 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE; 73 74 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) 75 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED; 76 } 77 78 /* 79 * If the guest FPSIMD state was loaded, update the host's context 80 * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu 81 * so that they will be written back if the kernel clobbers them due to 82 * kernel-mode NEON before re-entry into the guest. 83 */ 84 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) 85 { 86 WARN_ON_ONCE(!irqs_disabled()); 87 88 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { 89 fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.gp_regs.fp_regs, 90 vcpu->arch.sve_state, 91 vcpu->arch.sve_max_vl); 92 93 clear_thread_flag(TIF_FOREIGN_FPSTATE); 94 update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu)); 95 } 96 } 97 98 /* 99 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the 100 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu 101 * disappears and another task or vcpu appears that recycles the same 102 * struct fpsimd_state. 103 */ 104 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) 105 { 106 unsigned long flags; 107 bool host_has_sve = system_supports_sve(); 108 bool guest_has_sve = vcpu_has_sve(vcpu); 109 110 local_irq_save(flags); 111 112 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { 113 u64 *guest_zcr = &vcpu->arch.ctxt.sys_regs[ZCR_EL1]; 114 115 fpsimd_save_and_flush_cpu_state(); 116 117 if (guest_has_sve) 118 *guest_zcr = read_sysreg_s(SYS_ZCR_EL12); 119 } else if (host_has_sve) { 120 /* 121 * The FPSIMD/SVE state in the CPU has not been touched, and we 122 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been 123 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE 124 * for EL0. To avoid spurious traps, restore the trap state 125 * seen by kvm_arch_vcpu_load_fp(): 126 */ 127 if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED) 128 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN); 129 else 130 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0); 131 } 132 133 update_thread_flag(TIF_SVE, 134 vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE); 135 136 local_irq_restore(flags); 137 } 138