1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers
  4 *
  5 * Copyright 2018 Arm Limited
  6 * Author: Dave Martin <Dave.Martin@arm.com>
  7 */
  8#include <linux/irqflags.h>
  9#include <linux/sched.h>
 10#include <linux/kvm_host.h>
 11#include <asm/fpsimd.h>
 12#include <asm/kvm_asm.h>
 13#include <asm/kvm_hyp.h>
 14#include <asm/kvm_mmu.h>
 15#include <asm/sysreg.h>
 16
 17void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
 18{
 19	struct task_struct *p = vcpu->arch.parent_task;
 20	struct user_fpsimd_state *fpsimd;
 21
 22	if (!is_protected_kvm_enabled() || !p)
 23		return;
 24
 25	fpsimd = &p->thread.uw.fpsimd_state;
 26	kvm_unshare_hyp(fpsimd, fpsimd + 1);
 27	put_task_struct(p);
 28}
 29
 30/*
 31 * Called on entry to KVM_RUN unless this vcpu previously ran at least
 32 * once and the most recent prior KVM_RUN for this vcpu was called from
 33 * the same task as current (highly likely).
 34 *
 35 * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
 36 * such that on entering hyp the relevant parts of current are already
 37 * mapped.
 38 */
 39int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 40{
 41	int ret;
 42
 43	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
 44
 45	kvm_vcpu_unshare_task_fp(vcpu);
 46
 47	/* Make sure the host task fpsimd state is visible to hyp: */
 48	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
 49	if (ret)
 50		return ret;
 51
 52	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
 53
 54	/*
 55	 * We need to keep current's task_struct pinned until its data has been
 56	 * unshared with the hypervisor to make sure it is not re-used by the
 57	 * kernel and donated to someone else while already shared -- see
 58	 * kvm_vcpu_unshare_task_fp() for the matching put_task_struct().
 59	 */
 60	if (is_protected_kvm_enabled()) {
 61		get_task_struct(current);
 62		vcpu->arch.parent_task = current;
 63	}
 64
 65	return 0;
 66}
 67
 68/*
 69 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
 70 * The actual loading is done by the FPSIMD access trap taken to hyp.
 71 *
 72 * Here, we just set the correct metadata to indicate that the FPSIMD
 73 * state in the cpu regs (if any) belongs to current on the host.
 74 */
 75void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 76{
 77	BUG_ON(!current->mm);
 78
 79	if (!system_supports_fpsimd())
 80		return;
 81
 82	fpsimd_kvm_prepare();
 83
 84	vcpu->arch.fp_state = FP_STATE_HOST_OWNED;
 85
 86	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
 87	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
 88		vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
 89
 90	/*
 91	 * We don't currently support SME guests but if we leave
 92	 * things in streaming mode then when the guest starts running
 93	 * FPSIMD or SVE code it may generate SME traps so as a
 94	 * special case if we are in streaming mode we force the host
 95	 * state to be saved now and exit streaming mode so that we
 96	 * don't have to handle any SME traps for valid guest
 97	 * operations. Do this for ZA as well for now for simplicity.
 98	 */
 99	if (system_supports_sme()) {
100		vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
101		if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
102			vcpu_set_flag(vcpu, HOST_SME_ENABLED);
103
104		if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
105			vcpu->arch.fp_state = FP_STATE_FREE;
106			fpsimd_save_and_flush_cpu_state();
107		}
108	}
109}
110
111/*
112 * Called just before entering the guest once we are no longer preemptable
113 * and interrupts are disabled. If we have managed to run anything using
114 * FP while we were preemptible (such as off the back of an interrupt),
115 * then neither the host nor the guest own the FP hardware (and it was the
116 * responsibility of the code that used FP to save the existing state).
117 */
118void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
119{
120	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
121		vcpu->arch.fp_state = FP_STATE_FREE;
122}
123
124/*
125 * Called just after exiting the guest. If the guest FPSIMD state
126 * was loaded, update the host's context tracking data mark the CPU
127 * FPSIMD regs as dirty and belonging to vcpu so that they will be
128 * written back if the kernel clobbers them due to kernel-mode NEON
129 * before re-entry into the guest.
130 */
131void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
132{
133	struct cpu_fp_state fp_state;
134
135	WARN_ON_ONCE(!irqs_disabled());
136
137	if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
138
139		/*
140		 * Currently we do not support SME guests so SVCR is
141		 * always 0 and we just need a variable to point to.
142		 */
143		fp_state.st = &vcpu->arch.ctxt.fp_regs;
144		fp_state.sve_state = vcpu->arch.sve_state;
145		fp_state.sve_vl = vcpu->arch.sve_max_vl;
146		fp_state.za_state = NULL;
147		fp_state.svcr = &vcpu->arch.svcr;
148		fp_state.fp_type = &vcpu->arch.fp_type;
149
150		if (vcpu_has_sve(vcpu))
151			fp_state.to_save = FP_STATE_SVE;
152		else
153			fp_state.to_save = FP_STATE_FPSIMD;
154
155		fpsimd_bind_state_to_cpu(&fp_state);
156
157		clear_thread_flag(TIF_FOREIGN_FPSTATE);
158	}
159}
160
161/*
162 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
163 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
164 * disappears and another task or vcpu appears that recycles the same
165 * struct fpsimd_state.
166 */
167void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
168{
169	unsigned long flags;
170
171	local_irq_save(flags);
172
173	/*
174	 * If we have VHE then the Hyp code will reset CPACR_EL1 to
175	 * CPACR_EL1_DEFAULT and we need to reenable SME.
176	 */
177	if (has_vhe() && system_supports_sme()) {
178		/* Also restore EL0 state seen on entry */
179		if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
180			sysreg_clear_set(CPACR_EL1, 0,
181					 CPACR_EL1_SMEN_EL0EN |
182					 CPACR_EL1_SMEN_EL1EN);
183		else
184			sysreg_clear_set(CPACR_EL1,
185					 CPACR_EL1_SMEN_EL0EN,
186					 CPACR_EL1_SMEN_EL1EN);
187	}
188
189	if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
190		if (vcpu_has_sve(vcpu)) {
191			__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
192
193			/* Restore the VL that was saved when bound to the CPU */
194			if (!has_vhe())
195				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
196						       SYS_ZCR_EL1);
197		}
198
199		fpsimd_save_and_flush_cpu_state();
200	} else if (has_vhe() && system_supports_sve()) {
201		/*
202		 * The FPSIMD/SVE state in the CPU has not been touched, and we
203		 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
204		 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
205		 * for EL0.  To avoid spurious traps, restore the trap state
206		 * seen by kvm_arch_vcpu_load_fp():
207		 */
208		if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
209			sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
210		else
211			sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
212	}
213
214	local_irq_restore(flags);
215}