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_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 */
  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        vcpu->arch.host_thread_info = kern_hyp_va(ti);
  47        vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
  48error:
  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 */
  62void 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 */
  84void 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 */
 104void 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