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/kvm_host.h> 11 #include <asm/fpsimd.h> 12 #include <asm/kvm_asm.h> 13 #include <asm/kvm_hyp.h> 14 #include <asm/kvm_mmu.h> 15 #include <asm/sysreg.h> 16 17 void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu) 18 { 19 struct task_struct *p = vcpu->arch.parent_task; 20 struct user_fpsimd_state *fpsimd; 21 22 if (!is_protected_kvm_enabled() || !p) 23 return; 24 25 fpsimd = &p->thread.uw.fpsimd_state; 26 kvm_unshare_hyp(fpsimd, fpsimd + 1); 27 put_task_struct(p); 28 } 29 30 /* 31 * Called on entry to KVM_RUN unless this vcpu previously ran at least 32 * once and the most recent prior KVM_RUN for this vcpu was called from 33 * the same task as current (highly likely). 34 * 35 * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu), 36 * such that on entering hyp the relevant parts of current are already 37 * mapped. 38 */ 39 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu) 40 { 41 int ret; 42 43 struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state; 44 45 kvm_vcpu_unshare_task_fp(vcpu); 46 47 /* Make sure the host task fpsimd state is visible to hyp: */ 48 ret = kvm_share_hyp(fpsimd, fpsimd + 1); 49 if (ret) 50 return ret; 51 52 vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd); 53 54 /* 55 * We need to keep current's task_struct pinned until its data has been 56 * unshared with the hypervisor to make sure it is not re-used by the 57 * kernel and donated to someone else while already shared -- see 58 * kvm_vcpu_unshare_task_fp() for the matching put_task_struct(). 59 */ 60 if (is_protected_kvm_enabled()) { 61 get_task_struct(current); 62 vcpu->arch.parent_task = current; 63 } 64 65 return 0; 66 } 67 68 /* 69 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's. 70 * The actual loading is done by the FPSIMD access trap taken to hyp. 71 * 72 * Here, we just set the correct metadata to indicate that the FPSIMD 73 * state in the cpu regs (if any) belongs to current on the host. 74 */ 75 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) 76 { 77 BUG_ON(!current->mm); 78 79 if (!system_supports_fpsimd()) 80 return; 81 82 fpsimd_kvm_prepare(); 83 84 /* 85 * We will check TIF_FOREIGN_FPSTATE just before entering the 86 * guest in kvm_arch_vcpu_ctxflush_fp() and override this to 87 * FP_STATE_FREE if the flag set. 88 */ 89 vcpu->arch.fp_state = FP_STATE_HOST_OWNED; 90 91 vcpu_clear_flag(vcpu, HOST_SVE_ENABLED); 92 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) 93 vcpu_set_flag(vcpu, HOST_SVE_ENABLED); 94 95 if (system_supports_sme()) { 96 vcpu_clear_flag(vcpu, HOST_SME_ENABLED); 97 if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN) 98 vcpu_set_flag(vcpu, HOST_SME_ENABLED); 99 100 /* 101 * If PSTATE.SM is enabled then save any pending FP 102 * state and disable PSTATE.SM. If we leave PSTATE.SM 103 * enabled and the guest does not enable SME via 104 * CPACR_EL1.SMEN then operations that should be valid 105 * may generate SME traps from EL1 to EL1 which we 106 * can't intercept and which would confuse the guest. 107 * 108 * Do the same for PSTATE.ZA in the case where there 109 * is state in the registers which has not already 110 * been saved, this is very unlikely to happen. 111 */ 112 if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) { 113 vcpu->arch.fp_state = FP_STATE_FREE; 114 fpsimd_save_and_flush_cpu_state(); 115 } 116 } 117 } 118 119 /* 120 * Called just before entering the guest once we are no longer preemptable 121 * and interrupts are disabled. If we have managed to run anything using 122 * FP while we were preemptible (such as off the back of an interrupt), 123 * then neither the host nor the guest own the FP hardware (and it was the 124 * responsibility of the code that used FP to save the existing state). 125 */ 126 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu) 127 { 128 if (test_thread_flag(TIF_FOREIGN_FPSTATE)) 129 vcpu->arch.fp_state = FP_STATE_FREE; 130 } 131 132 /* 133 * Called just after exiting the guest. If the guest FPSIMD state 134 * was loaded, update the host's context tracking data mark the CPU 135 * FPSIMD regs as dirty and belonging to vcpu so that they will be 136 * written back if the kernel clobbers them due to kernel-mode NEON 137 * before re-entry into the guest. 138 */ 139 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) 140 { 141 struct cpu_fp_state fp_state; 142 143 WARN_ON_ONCE(!irqs_disabled()); 144 145 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) { 146 147 /* 148 * Currently we do not support SME guests so SVCR is 149 * always 0 and we just need a variable to point to. 150 */ 151 fp_state.st = &vcpu->arch.ctxt.fp_regs; 152 fp_state.sve_state = vcpu->arch.sve_state; 153 fp_state.sve_vl = vcpu->arch.sve_max_vl; 154 fp_state.sme_state = NULL; 155 fp_state.svcr = &vcpu->arch.svcr; 156 fp_state.fp_type = &vcpu->arch.fp_type; 157 158 if (vcpu_has_sve(vcpu)) 159 fp_state.to_save = FP_STATE_SVE; 160 else 161 fp_state.to_save = FP_STATE_FPSIMD; 162 163 fpsimd_bind_state_to_cpu(&fp_state); 164 165 clear_thread_flag(TIF_FOREIGN_FPSTATE); 166 } 167 } 168 169 /* 170 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the 171 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu 172 * disappears and another task or vcpu appears that recycles the same 173 * struct fpsimd_state. 174 */ 175 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) 176 { 177 unsigned long flags; 178 179 local_irq_save(flags); 180 181 /* 182 * If we have VHE then the Hyp code will reset CPACR_EL1 to 183 * the default value and we need to reenable SME. 184 */ 185 if (has_vhe() && system_supports_sme()) { 186 /* Also restore EL0 state seen on entry */ 187 if (vcpu_get_flag(vcpu, HOST_SME_ENABLED)) 188 sysreg_clear_set(CPACR_EL1, 0, 189 CPACR_EL1_SMEN_EL0EN | 190 CPACR_EL1_SMEN_EL1EN); 191 else 192 sysreg_clear_set(CPACR_EL1, 193 CPACR_EL1_SMEN_EL0EN, 194 CPACR_EL1_SMEN_EL1EN); 195 isb(); 196 } 197 198 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) { 199 if (vcpu_has_sve(vcpu)) { 200 __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR); 201 202 /* Restore the VL that was saved when bound to the CPU */ 203 if (!has_vhe()) 204 sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1, 205 SYS_ZCR_EL1); 206 } 207 208 fpsimd_save_and_flush_cpu_state(); 209 } else if (has_vhe() && system_supports_sve()) { 210 /* 211 * The FPSIMD/SVE state in the CPU has not been touched, and we 212 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been 213 * reset by kvm_reset_cptr_el2() in the Hyp code, disabling SVE 214 * for EL0. To avoid spurious traps, restore the trap state 215 * seen by kvm_arch_vcpu_load_fp(): 216 */ 217 if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED)) 218 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN); 219 else 220 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0); 221 } 222 223 local_irq_restore(flags); 224 } 225