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
kvm_vcpu_unshare_task_fp(struct kvm_vcpu * vcpu)17 void 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 */
kvm_arch_vcpu_run_map_fp(struct kvm_vcpu * vcpu)39 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
40 {
41 int ret;
42
43 struct user_fpsimd_state *fpsimd = ¤t->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 */
kvm_arch_vcpu_load_fp(struct kvm_vcpu * vcpu)75 void 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 /*
85 * We will check TIF_FOREIGN_FPSTATE just before entering the
86 * guest in kvm_arch_vcpu_ctxflush_fp() and override this to
87 * FP_STATE_FREE if the flag set.
88 */
89 vcpu->arch.fp_state = FP_STATE_HOST_OWNED;
90
91 vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
92 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
93 vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
94
95 if (system_supports_sme()) {
96 vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
97 if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
98 vcpu_set_flag(vcpu, HOST_SME_ENABLED);
99
100 /*
101 * If PSTATE.SM is enabled then save any pending FP
102 * state and disable PSTATE.SM. If we leave PSTATE.SM
103 * enabled and the guest does not enable SME via
104 * CPACR_EL1.SMEN then operations that should be valid
105 * may generate SME traps from EL1 to EL1 which we
106 * can't intercept and which would confuse the guest.
107 *
108 * Do the same for PSTATE.ZA in the case where there
109 * is state in the registers which has not already
110 * been saved, this is very unlikely to happen.
111 */
112 if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
113 vcpu->arch.fp_state = FP_STATE_FREE;
114 fpsimd_save_and_flush_cpu_state();
115 }
116 }
117 }
118
119 /*
120 * Called just before entering the guest once we are no longer preemptable
121 * and interrupts are disabled. If we have managed to run anything using
122 * FP while we were preemptible (such as off the back of an interrupt),
123 * then neither the host nor the guest own the FP hardware (and it was the
124 * responsibility of the code that used FP to save the existing state).
125 */
kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu * vcpu)126 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
127 {
128 if (test_thread_flag(TIF_FOREIGN_FPSTATE))
129 vcpu->arch.fp_state = FP_STATE_FREE;
130 }
131
132 /*
133 * Called just after exiting the guest. If the guest FPSIMD state
134 * was loaded, update the host's context tracking data mark the CPU
135 * FPSIMD regs as dirty and belonging to vcpu so that they will be
136 * written back if the kernel clobbers them due to kernel-mode NEON
137 * before re-entry into the guest.
138 */
kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu * vcpu)139 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
140 {
141 struct cpu_fp_state fp_state;
142
143 WARN_ON_ONCE(!irqs_disabled());
144
145 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
146
147 /*
148 * Currently we do not support SME guests so SVCR is
149 * always 0 and we just need a variable to point to.
150 */
151 fp_state.st = &vcpu->arch.ctxt.fp_regs;
152 fp_state.sve_state = vcpu->arch.sve_state;
153 fp_state.sve_vl = vcpu->arch.sve_max_vl;
154 fp_state.sme_state = NULL;
155 fp_state.svcr = &vcpu->arch.svcr;
156 fp_state.fp_type = &vcpu->arch.fp_type;
157
158 if (vcpu_has_sve(vcpu))
159 fp_state.to_save = FP_STATE_SVE;
160 else
161 fp_state.to_save = FP_STATE_FPSIMD;
162
163 fpsimd_bind_state_to_cpu(&fp_state);
164
165 clear_thread_flag(TIF_FOREIGN_FPSTATE);
166 }
167 }
168
169 /*
170 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
171 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
172 * disappears and another task or vcpu appears that recycles the same
173 * struct fpsimd_state.
174 */
kvm_arch_vcpu_put_fp(struct kvm_vcpu * vcpu)175 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
176 {
177 unsigned long flags;
178
179 local_irq_save(flags);
180
181 /*
182 * If we have VHE then the Hyp code will reset CPACR_EL1 to
183 * the default value and we need to reenable SME.
184 */
185 if (has_vhe() && system_supports_sme()) {
186 /* Also restore EL0 state seen on entry */
187 if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
188 sysreg_clear_set(CPACR_EL1, 0,
189 CPACR_EL1_SMEN_EL0EN |
190 CPACR_EL1_SMEN_EL1EN);
191 else
192 sysreg_clear_set(CPACR_EL1,
193 CPACR_EL1_SMEN_EL0EN,
194 CPACR_EL1_SMEN_EL1EN);
195 isb();
196 }
197
198 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
199 if (vcpu_has_sve(vcpu)) {
200 __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
201
202 /* Restore the VL that was saved when bound to the CPU */
203 if (!has_vhe())
204 sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
205 SYS_ZCR_EL1);
206 }
207
208 fpsimd_save_and_flush_cpu_state();
209 } else if (has_vhe() && system_supports_sve()) {
210 /*
211 * The FPSIMD/SVE state in the CPU has not been touched, and we
212 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
213 * reset by kvm_reset_cptr_el2() in the Hyp code, disabling SVE
214 * for EL0. To avoid spurious traps, restore the trap state
215 * seen by kvm_arch_vcpu_load_fp():
216 */
217 if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
218 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
219 else
220 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
221 }
222
223 local_irq_restore(flags);
224 }
225