// SPDX-License-Identifier: GPL-2.0 /* * arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers * * Copyright 2018 Arm Limited * Author: Dave Martin */ #include #include #include #include #include #include #include #include void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu) { struct task_struct *p = vcpu->arch.parent_task; struct user_fpsimd_state *fpsimd; if (!is_protected_kvm_enabled() || !p) return; fpsimd = &p->thread.uw.fpsimd_state; kvm_unshare_hyp(fpsimd, fpsimd + 1); put_task_struct(p); } /* * 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 user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state; kvm_vcpu_unshare_task_fp(vcpu); /* Make sure the host task fpsimd state is visible to hyp: */ ret = kvm_share_hyp(fpsimd, fpsimd + 1); if (ret) return ret; vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd); /* * We need to keep current's task_struct pinned until its data has been * unshared with the hypervisor to make sure it is not re-used by the * kernel and donated to someone else while already shared -- see * kvm_vcpu_unshare_task_fp() for the matching put_task_struct(). */ if (is_protected_kvm_enabled()) { get_task_struct(current); vcpu->arch.parent_task = current; } return 0; } /* * 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. */ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) { BUG_ON(!current->mm); BUG_ON(test_thread_flag(TIF_SVE)); if (!system_supports_fpsimd()) return; vcpu->arch.fp_state = FP_STATE_HOST_OWNED; vcpu_clear_flag(vcpu, HOST_SVE_ENABLED); if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) vcpu_set_flag(vcpu, HOST_SVE_ENABLED); /* * We don't currently support SME guests but if we leave * things in streaming mode then when the guest starts running * FPSIMD or SVE code it may generate SME traps so as a * special case if we are in streaming mode we force the host * state to be saved now and exit streaming mode so that we * don't have to handle any SME traps for valid guest * operations. Do this for ZA as well for now for simplicity. */ if (system_supports_sme()) { vcpu_clear_flag(vcpu, HOST_SME_ENABLED); if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN) vcpu_set_flag(vcpu, HOST_SME_ENABLED); if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) { vcpu->arch.fp_state = FP_STATE_FREE; fpsimd_save_and_flush_cpu_state(); } } } /* * Called just before entering the guest once we are no longer preemptable * and interrupts are disabled. If we have managed to run anything using * FP while we were preemptible (such as off the back of an interrupt), * then neither the host nor the guest own the FP hardware (and it was the * responsibility of the code that used FP to save the existing state). */ void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu) { if (test_thread_flag(TIF_FOREIGN_FPSTATE)) vcpu->arch.fp_state = FP_STATE_FREE; } /* * Called just after exiting the guest. 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.fp_state == FP_STATE_GUEST_OWNED) { /* * Currently we do not support SME guests so SVCR is * always 0 and we just need a variable to point to. */ fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs, vcpu->arch.sve_state, vcpu->arch.sve_max_vl, NULL, 0, &vcpu->arch.svcr); 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; local_irq_save(flags); /* * If we have VHE then the Hyp code will reset CPACR_EL1 to * CPACR_EL1_DEFAULT and we need to reenable SME. */ if (has_vhe() && system_supports_sme()) { /* Also restore EL0 state seen on entry */ if (vcpu_get_flag(vcpu, HOST_SME_ENABLED)) sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_SMEN_EL0EN | CPACR_EL1_SMEN_EL1EN); else sysreg_clear_set(CPACR_EL1, CPACR_EL1_SMEN_EL0EN, CPACR_EL1_SMEN_EL1EN); } if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) { if (vcpu_has_sve(vcpu)) { __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR); /* Restore the VL that was saved when bound to the CPU */ if (!has_vhe()) sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1, SYS_ZCR_EL1); } fpsimd_save_and_flush_cpu_state(); } else if (has_vhe() && system_supports_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_get_flag(vcpu, 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, 0); local_irq_restore(flags); }