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 /* 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 struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state; 29 int ret; 30 31 /* pKVM has its own tracking of the host fpsimd state. */ 32 if (is_protected_kvm_enabled()) 33 return 0; 34 35 /* Make sure the host task fpsimd state is visible to hyp: */ 36 ret = kvm_share_hyp(fpsimd, fpsimd + 1); 37 if (ret) 38 return ret; 39 40 return 0; 41 } 42 43 /* 44 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's. 45 * The actual loading is done by the FPSIMD access trap taken to hyp. 46 * 47 * Here, we just set the correct metadata to indicate that the FPSIMD 48 * state in the cpu regs (if any) belongs to current on the host. 49 */ 50 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) 51 { 52 BUG_ON(!current->mm); 53 54 if (!system_supports_fpsimd()) 55 return; 56 57 /* 58 * Ensure that any host FPSIMD/SVE/SME state is saved and unbound such 59 * that the host kernel is responsible for restoring this state upon 60 * return to userspace, and the hyp code doesn't need to save anything. 61 * 62 * When the host may use SME, fpsimd_save_and_flush_cpu_state() ensures 63 * that PSTATE.{SM,ZA} == {0,0}. 64 */ 65 fpsimd_save_and_flush_cpu_state(); 66 *host_data_ptr(fp_owner) = FP_STATE_FREE; 67 68 WARN_ON_ONCE(system_supports_sme() && read_sysreg_s(SYS_SVCR)); 69 } 70 71 /* 72 * Called just before entering the guest once we are no longer preemptible 73 * and interrupts are disabled. If we have managed to run anything using 74 * FP while we were preemptible (such as off the back of an interrupt), 75 * then neither the host nor the guest own the FP hardware (and it was the 76 * responsibility of the code that used FP to save the existing state). 77 */ 78 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu) 79 { 80 if (test_thread_flag(TIF_FOREIGN_FPSTATE)) 81 *host_data_ptr(fp_owner) = FP_STATE_FREE; 82 } 83 84 /* 85 * Called just after exiting the guest. If the guest FPSIMD state 86 * was loaded, update the host's context tracking data mark the CPU 87 * FPSIMD regs as dirty and belonging to vcpu so that they will be 88 * written back if the kernel clobbers them due to kernel-mode NEON 89 * before re-entry into the guest. 90 */ 91 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) 92 { 93 struct cpu_fp_state fp_state; 94 95 WARN_ON_ONCE(!irqs_disabled()); 96 97 if (guest_owns_fp_regs()) { 98 /* 99 * Currently we do not support SME guests so SVCR is 100 * always 0 and we just need a variable to point to. 101 */ 102 fp_state.st = &vcpu->arch.ctxt.fp_regs; 103 fp_state.sve_state = vcpu->arch.sve_state; 104 fp_state.sve_vl = vcpu->arch.sve_max_vl; 105 fp_state.sme_state = NULL; 106 fp_state.svcr = __ctxt_sys_reg(&vcpu->arch.ctxt, SVCR); 107 fp_state.fpmr = __ctxt_sys_reg(&vcpu->arch.ctxt, FPMR); 108 fp_state.fp_type = &vcpu->arch.fp_type; 109 110 if (vcpu_has_sve(vcpu)) 111 fp_state.to_save = FP_STATE_SVE; 112 else 113 fp_state.to_save = FP_STATE_FPSIMD; 114 115 fpsimd_bind_state_to_cpu(&fp_state); 116 117 clear_thread_flag(TIF_FOREIGN_FPSTATE); 118 } 119 } 120 121 /* 122 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the 123 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu 124 * disappears and another task or vcpu appears that recycles the same 125 * struct fpsimd_state. 126 */ 127 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) 128 { 129 unsigned long flags; 130 131 local_irq_save(flags); 132 133 if (guest_owns_fp_regs()) { 134 /* 135 * Flush (save and invalidate) the fpsimd/sve state so that if 136 * the host tries to use fpsimd/sve, it's not using stale data 137 * from the guest. 138 * 139 * Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the 140 * context unconditionally, in both nVHE and VHE. This allows 141 * the kernel to restore the fpsimd/sve state, including ZCR_EL1 142 * when needed. 143 */ 144 fpsimd_save_and_flush_cpu_state(); 145 } 146 147 local_irq_restore(flags); 148 } 149