LXR linux/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 */
  27int 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);
  59error:
  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 */
  73void 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 */
  95void 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 */
 115void 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}
 153