arch/arm64/kvm/fpsimd.c

   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_hyp.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 = &current->thread_info;
  32         struct user_fpsimd_state *fpsimd = &current->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         if (vcpu->arch.sve_state) {
  47                 void *sve_end;
  48
  49                 sve_end = vcpu->arch.sve_state + vcpu_sve_state_size(vcpu);
  50
  51                 ret = create_hyp_mappings(vcpu->arch.sve_state, sve_end,
  52                                           PAGE_HYP);
  53                 if (ret)
  54                         goto error;
  55         }
  56
  57         vcpu->arch.host_thread_info = kern_hyp_va(ti);
  58         vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
  59 error:
  60         return ret;
  61 }
  62
  63 /*
  64  * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
  65  * The actual loading is done by the FPSIMD access trap taken to hyp.
  66  *
  67  * Here, we just set the correct metadata to indicate that the FPSIMD
  68  * state in the cpu regs (if any) belongs to current on the host.
  69  *
  70  * TIF_SVE is backed up here, since it may get clobbered with guest state.
  71  * This flag is restored by kvm_arch_vcpu_put_fp(vcpu).
  72  */
  73 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
  74 {
  75         BUG_ON(!current->mm);
  76
  77         vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
  78                               KVM_ARM64_HOST_SVE_IN_USE |
  79                               KVM_ARM64_HOST_SVE_ENABLED);
  80         vcpu->arch.flags |= KVM_ARM64_FP_HOST;
  81
  82         if (test_thread_flag(TIF_SVE))
  83                 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE;
  84
  85         if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
  86                 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
  87 }
  88
  89 /*
  90  * If the guest FPSIMD state was loaded, update the host's context
  91  * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
  92  * so that they will be written back if the kernel clobbers them due to
  93  * kernel-mode NEON before re-entry into the guest.
  94  */
  95 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
  96 {
  97         WARN_ON_ONCE(!irqs_disabled());
  98
  99         if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
 100                 fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
 101                                          vcpu->arch.sve_state,
 102                                          vcpu->arch.sve_max_vl);
 103
 104                 clear_thread_flag(TIF_FOREIGN_FPSTATE);
 105                 update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
 106         }
 107 }
 108
 109 /*
 110  * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
 111  * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
 112  * disappears and another task or vcpu appears that recycles the same
 113  * struct fpsimd_state.
 114  */
 115 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 116 {
 117         unsigned long flags;
 118         bool host_has_sve = system_supports_sve();
 119         bool guest_has_sve = vcpu_has_sve(vcpu);
 120
 121         local_irq_save(flags);
 122
 123         if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
 124                 if (guest_has_sve) {
 125                         __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
 126
 127                         /* Restore the VL that was saved when bound to the CPU */
 128                         if (!has_vhe())
 129                                 sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
 130                                                        SYS_ZCR_EL1);
 131                 }
 132
 133                 fpsimd_save_and_flush_cpu_state();
 134         } else if (has_vhe() && host_has_sve) {
 135                 /*
 136                  * The FPSIMD/SVE state in the CPU has not been touched, and we
 137                  * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
 138                  * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
 139                  * for EL0.  To avoid spurious traps, restore the trap state
 140                  * seen by kvm_arch_vcpu_load_fp():
 141                  */
 142                 if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
 143                         sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
 144                 else
 145                         sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
 146         }
 147
 148         update_thread_flag(TIF_SVE,
 149                            vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE);
 150
 151         local_irq_restore(flags);
 152 }