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Diffstat (limited to 'arch/arm64/kvm/fpsimd.c')
| -rw-r--r-- | arch/arm64/kvm/fpsimd.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c new file mode 100644 index 000000000..ec8e44948 --- /dev/null +++ b/arch/arm64/kvm/fpsimd.c @@ -0,0 +1,205 @@ +// 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/kvm_host.h> +#include <asm/fpsimd.h> +#include <asm/kvm_asm.h> +#include <asm/kvm_hyp.h> +#include <asm/kvm_mmu.h> +#include <asm/sysreg.h> + +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); +} |