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Diffstat (limited to 'arch/arm64/kvm/fpsimd.c')
| -rw-r--r-- | arch/arm64/kvm/fpsimd.c | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c new file mode 100644 index 000000000000..15e17aca1dec --- /dev/null +++ b/arch/arm64/kvm/fpsimd.c @@ -0,0 +1,122 @@ +// 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> + +/* + * 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); + + if (!system_supports_fpsimd()) + return; + + /* + * Ensure that any host FPSIMD/SVE/SME state is saved and unbound such + * that the host kernel is responsible for restoring this state upon + * return to userspace, and the hyp code doesn't need to save anything. + * + * When the host may use SME, fpsimd_save_and_flush_cpu_state() ensures + * that PSTATE.{SM,ZA} == {0,0}. + */ + fpsimd_save_and_flush_cpu_state(); + *host_data_ptr(fp_owner) = FP_STATE_FREE; + + WARN_ON_ONCE(system_supports_sme() && read_sysreg_s(SYS_SVCR)); +} + +/* + * Called just before entering the guest once we are no longer preemptible + * 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)) + *host_data_ptr(fp_owner) = 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) +{ + struct cpu_fp_state fp_state; + + WARN_ON_ONCE(!irqs_disabled()); + + if (guest_owns_fp_regs()) { + /* + * Currently we do not support SME guests so SVCR is + * always 0 and we just need a variable to point to. + */ + fp_state.st = &vcpu->arch.ctxt.fp_regs; + fp_state.sve_state = vcpu->arch.sve_state; + fp_state.sve_vl = vcpu->arch.sve_max_vl; + fp_state.sme_state = NULL; + fp_state.svcr = __ctxt_sys_reg(&vcpu->arch.ctxt, SVCR); + fp_state.fpmr = __ctxt_sys_reg(&vcpu->arch.ctxt, FPMR); + fp_state.fp_type = &vcpu->arch.fp_type; + + if (vcpu_has_sve(vcpu)) + fp_state.to_save = FP_STATE_SVE; + else + fp_state.to_save = FP_STATE_FPSIMD; + + fpsimd_bind_state_to_cpu(&fp_state); + + clear_thread_flag(TIF_FOREIGN_FPSTATE); + } +} + +/* + * 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 (guest_owns_fp_regs()) { + /* + * Flush (save and invalidate) the fpsimd/sve state so that if + * the host tries to use fpsimd/sve, it's not using stale data + * from the guest. + * + * Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the + * context unconditionally, in both nVHE and VHE. This allows + * the kernel to restore the fpsimd/sve state, including ZCR_EL1 + * when needed. + */ + fpsimd_save_and_flush_cpu_state(); + } + + local_irq_restore(flags); +} |