0495067420
The current FPSIMD/SVE context handling support for non-task (i.e., KVM vcpu) contexts does not take SVE into account. This means that only task contexts can safely use SVE at present. In preparation for enabling KVM guests to use SVE, it is necessary to keep track of SVE state for non-task contexts too. This patch adds the necessary support, removing assumptions from the context switch code about the location of the SVE context storage. When binding a vcpu context, its vector length is arbitrarily specified as SVE_VL_MIN for now. In any case, because TIF_SVE is presently cleared at vcpu context bind time, the specified vector length will not be used for anything yet. In later patches TIF_SVE will be set here as appropriate, and the appropriate maximum vector length for the vcpu will be passed when binding. Signed-off-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Julien Grall <julien.grall@arm.com> Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
132 lines
3.8 KiB
C
132 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers
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*
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* Copyright 2018 Arm Limited
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* Author: Dave Martin <Dave.Martin@arm.com>
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*/
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#include <linux/irqflags.h>
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#include <linux/sched.h>
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#include <linux/thread_info.h>
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#include <linux/kvm_host.h>
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#include <asm/fpsimd.h>
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#include <asm/kvm_asm.h>
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#include <asm/kvm_host.h>
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#include <asm/kvm_mmu.h>
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#include <asm/sysreg.h>
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/*
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* Called on entry to KVM_RUN unless this vcpu previously ran at least
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* once and the most recent prior KVM_RUN for this vcpu was called from
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* the same task as current (highly likely).
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*
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* This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
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* such that on entering hyp the relevant parts of current are already
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* mapped.
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*/
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int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
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{
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int ret;
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struct thread_info *ti = ¤t->thread_info;
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struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state;
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/*
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* Make sure the host task thread flags and fpsimd state are
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* visible to hyp:
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*/
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ret = create_hyp_mappings(ti, ti + 1, PAGE_HYP);
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if (ret)
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goto error;
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ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP);
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if (ret)
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goto error;
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vcpu->arch.host_thread_info = kern_hyp_va(ti);
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vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
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error:
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return ret;
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}
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/*
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* Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
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* The actual loading is done by the FPSIMD access trap taken to hyp.
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*
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* Here, we just set the correct metadata to indicate that the FPSIMD
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* state in the cpu regs (if any) belongs to current on the host.
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*
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* TIF_SVE is backed up here, since it may get clobbered with guest state.
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* This flag is restored by kvm_arch_vcpu_put_fp(vcpu).
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*/
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void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
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{
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BUG_ON(!current->mm);
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vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
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KVM_ARM64_HOST_SVE_IN_USE |
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KVM_ARM64_HOST_SVE_ENABLED);
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vcpu->arch.flags |= KVM_ARM64_FP_HOST;
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if (test_thread_flag(TIF_SVE))
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vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE;
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if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
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vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
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}
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/*
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* If the guest FPSIMD state was loaded, update the host's context
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* tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
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* so that they will be written back if the kernel clobbers them due to
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* kernel-mode NEON before re-entry into the guest.
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*/
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void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
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{
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WARN_ON_ONCE(!irqs_disabled());
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if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
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fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.gp_regs.fp_regs,
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NULL, SVE_VL_MIN);
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clear_thread_flag(TIF_FOREIGN_FPSTATE);
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clear_thread_flag(TIF_SVE);
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}
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}
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/*
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* Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
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* cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
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* disappears and another task or vcpu appears that recycles the same
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* struct fpsimd_state.
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*/
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void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
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{
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unsigned long flags;
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local_irq_save(flags);
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if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
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/* Clean guest FP state to memory and invalidate cpu view */
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fpsimd_save();
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fpsimd_flush_cpu_state();
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} else if (system_supports_sve()) {
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/*
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* The FPSIMD/SVE state in the CPU has not been touched, and we
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* have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
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* reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
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* for EL0. To avoid spurious traps, restore the trap state
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* seen by kvm_arch_vcpu_load_fp():
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*/
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if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
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sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
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else
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sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
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}
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update_thread_flag(TIF_SVE,
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vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE);
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local_irq_restore(flags);
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}
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