diff options
Diffstat (limited to 'arch/arm64/kvm/fpsimd.c')
| -rw-r--r-- | arch/arm64/kvm/fpsimd.c | 134 |
1 files changed, 134 insertions, 0 deletions
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c new file mode 100644 index 000000000..3e081d556 --- /dev/null +++ b/arch/arm64/kvm/fpsimd.c @@ -0,0 +1,134 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers + * + * Copyright 2018 Arm Limited + * Author: Dave Martin <Dave.Martin@arm.com> + */ +#include <linux/irqflags.h> +#include <linux/sched.h> +#include <linux/thread_info.h> +#include <linux/kvm_host.h> +#include <asm/fpsimd.h> +#include <asm/kvm_asm.h> +#include <asm/kvm_mmu.h> +#include <asm/sysreg.h> + +/* + * Called on entry to KVM_RUN unless this vcpu previously ran at least + * once and the most recent prior KVM_RUN for this vcpu was called from + * the same task as current (highly likely). + * + * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu), + * such that on entering hyp the relevant parts of current are already + * mapped. + */ +int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu) +{ + int ret; + + struct thread_info *ti = ¤t->thread_info; + struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state; + + /* + * Make sure the host task thread flags and fpsimd state are + * visible to hyp: + */ + ret = create_hyp_mappings(ti, ti + 1, PAGE_HYP); + if (ret) + goto error; + + ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP); + if (ret) + goto error; + + vcpu->arch.host_thread_info = kern_hyp_va(ti); + vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd); +error: + return ret; +} + +/* + * Prepare vcpu for saving the host's FPSIMD state and loading the guest's. + * The actual loading is done by the FPSIMD access trap taken to hyp. + * + * Here, we just set the correct metadata to indicate that the FPSIMD + * state in the cpu regs (if any) belongs to current on the host. + * + * TIF_SVE is backed up here, since it may get clobbered with guest state. + * This flag is restored by kvm_arch_vcpu_put_fp(vcpu). + */ +void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) +{ + BUG_ON(!current->mm); + + vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED | + KVM_ARM64_HOST_SVE_IN_USE | + KVM_ARM64_HOST_SVE_ENABLED); + vcpu->arch.flags |= KVM_ARM64_FP_HOST; + + if (test_thread_flag(TIF_SVE)) + vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE; + + if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) + vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED; +} + +/* + * If the guest FPSIMD state was loaded, update the host's context + * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu + * so that they will be written back if the kernel clobbers them due to + * kernel-mode NEON before re-entry into the guest. + */ +void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) +{ + WARN_ON_ONCE(!irqs_disabled()); + + if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { + fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs, + vcpu->arch.sve_state, + vcpu->arch.sve_max_vl); + + clear_thread_flag(TIF_FOREIGN_FPSTATE); + update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu)); + } +} + +/* + * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the + * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu + * disappears and another task or vcpu appears that recycles the same + * struct fpsimd_state. + */ +void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) +{ + unsigned long flags; + bool host_has_sve = system_supports_sve(); + bool guest_has_sve = vcpu_has_sve(vcpu); + + local_irq_save(flags); + + if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { + fpsimd_save_and_flush_cpu_state(); + + if (guest_has_sve) + __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_s(SYS_ZCR_EL12); + } else if (host_has_sve) { + /* + * The FPSIMD/SVE state in the CPU has not been touched, and we + * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been + * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE + * for EL0. To avoid spurious traps, restore the trap state + * seen by kvm_arch_vcpu_load_fp(): + */ + if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED) + sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN); + else + sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0); + } + + update_thread_flag(TIF_SVE, + vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE); + + local_irq_restore(flags); +} |