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 BUG_ON(test_thread_flag(TIF_SVE));
79
80 if (!system_supports_fpsimd())
81 return;
82
83 vcpu->arch.fp_state = FP_STATE_HOST_OWNED;
84
85 vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
86 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
87 vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
88
89 /*
90 * We don't currently support SME guests but if we leave
91 * things in streaming mode then when the guest starts running
92 * FPSIMD or SVE code it may generate SME traps so as a
93 * special case if we are in streaming mode we force the host
94 * state to be saved now and exit streaming mode so that we
95 * don't have to handle any SME traps for valid guest
96 * operations. Do this for ZA as well for now for simplicity.
97 */
98 if (system_supports_sme()) {
99 vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
100 if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
101 vcpu_set_flag(vcpu, HOST_SME_ENABLED);
102
103 if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
104 vcpu->arch.fp_state = FP_STATE_FREE;
105 fpsimd_save_and_flush_cpu_state();
106 }
107 }
108 }
109
110 /*
111 * Called just before entering the guest once we are no longer preemptable
112 * and interrupts are disabled. If we have managed to run anything using
113 * FP while we were preemptible (such as off the back of an interrupt),
114 * then neither the host nor the guest own the FP hardware (and it was the
115 * responsibility of the code that used FP to save the existing state).
116 */
kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu * vcpu)117 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
118 {
119 if (test_thread_flag(TIF_FOREIGN_FPSTATE))
120 vcpu->arch.fp_state = FP_STATE_FREE;
121 }
122
123 /*
124 * Called just after exiting the guest. If the guest FPSIMD state
125 * was loaded, update the host's context tracking data mark the CPU
126 * FPSIMD regs as dirty and belonging to vcpu so that they will be
127 * written back if the kernel clobbers them due to kernel-mode NEON
128 * before re-entry into the guest.
129 */
kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu * vcpu)130 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
131 {
132 WARN_ON_ONCE(!irqs_disabled());
133
134 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
135 /*
136 * Currently we do not support SME guests so SVCR is
137 * always 0 and we just need a variable to point to.
138 */
139 fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
140 vcpu->arch.sve_state,
141 vcpu->arch.sve_max_vl,
142 NULL, 0, &vcpu->arch.svcr);
143
144 clear_thread_flag(TIF_FOREIGN_FPSTATE);
145 update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
146 }
147 }
148
149 /*
150 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
151 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
152 * disappears and another task or vcpu appears that recycles the same
153 * struct fpsimd_state.
154 */
kvm_arch_vcpu_put_fp(struct kvm_vcpu * vcpu)155 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
156 {
157 unsigned long flags;
158
159 local_irq_save(flags);
160
161 /*
162 * If we have VHE then the Hyp code will reset CPACR_EL1 to
163 * CPACR_EL1_DEFAULT and we need to reenable SME.
164 */
165 if (has_vhe() && system_supports_sme()) {
166 /* Also restore EL0 state seen on entry */
167 if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
168 sysreg_clear_set(CPACR_EL1, 0,
169 CPACR_EL1_SMEN_EL0EN |
170 CPACR_EL1_SMEN_EL1EN);
171 else
172 sysreg_clear_set(CPACR_EL1,
173 CPACR_EL1_SMEN_EL0EN,
174 CPACR_EL1_SMEN_EL1EN);
175 }
176
177 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
178 if (vcpu_has_sve(vcpu)) {
179 __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
180
181 /* Restore the VL that was saved when bound to the CPU */
182 if (!has_vhe())
183 sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
184 SYS_ZCR_EL1);
185 }
186
187 fpsimd_save_and_flush_cpu_state();
188 } else if (has_vhe() && system_supports_sve()) {
189 /*
190 * The FPSIMD/SVE state in the CPU has not been touched, and we
191 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
192 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
193 * for EL0. To avoid spurious traps, restore the trap state
194 * seen by kvm_arch_vcpu_load_fp():
195 */
196 if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
197 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
198 else
199 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
200 }
201
202 update_thread_flag(TIF_SVE, 0);
203
204 local_irq_restore(flags);
205 }
206