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This patch adds SVE context saving to the hyp FPSIMD context switch path. This means that it is no longer necessary to save the host SVE state in advance of entering the guest, when in use. In order to avoid adding pointless complexity to the code, VHE is assumed if SVE is in use. VHE is an architectural prerequisite for SVE, so there is no good reason to turn CONFIG_ARM64_VHE off in kernels that support both SVE and KVM. Historically, software models exist that can expose the architecturally invalid configuration of SVE without VHE, so if this situation is detected at kvm_init() time then KVM will be disabled. Signed-off-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
111 lines
3.2 KiB
C
111 lines
3.2 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/bottom_half.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/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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/*
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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 | KVM_ARM64_HOST_SVE_IN_USE);
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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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}
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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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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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local_bh_disable();
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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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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 (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
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/* Ensure user trap controls are correctly restored */
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fpsimd_bind_task_to_cpu();
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}
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local_bh_enable();
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}
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