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
17 /*
18 * Called on entry to KVM_RUN unless this vcpu previously ran at least
19 * once and the most recent prior KVM_RUN for this vcpu was called from
20 * the same task as current (highly likely).
21 *
22 * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
23 * such that on entering hyp the relevant parts of current are already
24 * mapped.
25 */
kvm_arch_vcpu_run_map_fp(struct kvm_vcpu * vcpu)26 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
27 {
28 struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state;
29 int ret;
30
31 /* pKVM has its own tracking of the host fpsimd state. */
32 if (is_protected_kvm_enabled())
33 return 0;
34
35 /* Make sure the host task fpsimd state is visible to hyp: */
36 ret = kvm_share_hyp(fpsimd, fpsimd + 1);
37 if (ret)
38 return ret;
39
40 vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
41
42 return 0;
43 }
44
45 /*
46 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
47 * The actual loading is done by the FPSIMD access trap taken to hyp.
48 *
49 * Here, we just set the correct metadata to indicate that the FPSIMD
50 * state in the cpu regs (if any) belongs to current on the host.
51 */
kvm_arch_vcpu_load_fp(struct kvm_vcpu * vcpu)52 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
53 {
54 BUG_ON(!current->mm);
55 BUG_ON(test_thread_flag(TIF_SVE));
56
57 if (!system_supports_fpsimd())
58 return;
59
60 vcpu->arch.fp_state = FP_STATE_HOST_OWNED;
61
62 vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
63 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
64 vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
65
66 /*
67 * We don't currently support SME guests but if we leave
68 * things in streaming mode then when the guest starts running
69 * FPSIMD or SVE code it may generate SME traps so as a
70 * special case if we are in streaming mode we force the host
71 * state to be saved now and exit streaming mode so that we
72 * don't have to handle any SME traps for valid guest
73 * operations. Do this for ZA as well for now for simplicity.
74 */
75 if (system_supports_sme()) {
76 vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
77 if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
78 vcpu_set_flag(vcpu, HOST_SME_ENABLED);
79
80 if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
81 vcpu->arch.fp_state = FP_STATE_FREE;
82 fpsimd_save_and_flush_cpu_state();
83 }
84 }
85 }
86
87 /*
88 * Called just before entering the guest once we are no longer preemptable
89 * and interrupts are disabled. If we have managed to run anything using
90 * FP while we were preemptible (such as off the back of an interrupt),
91 * then neither the host nor the guest own the FP hardware (and it was the
92 * responsibility of the code that used FP to save the existing state).
93 */
kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu * vcpu)94 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
95 {
96 if (test_thread_flag(TIF_FOREIGN_FPSTATE))
97 vcpu->arch.fp_state = FP_STATE_FREE;
98 }
99
100 /*
101 * Called just after exiting the guest. If the guest FPSIMD state
102 * was loaded, update the host's context tracking data mark the CPU
103 * FPSIMD regs as dirty and belonging to vcpu so that they will be
104 * written back if the kernel clobbers them due to kernel-mode NEON
105 * before re-entry into the guest.
106 */
kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu * vcpu)107 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
108 {
109 WARN_ON_ONCE(!irqs_disabled());
110
111 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
112 /*
113 * Currently we do not support SME guests so SVCR is
114 * always 0 and we just need a variable to point to.
115 */
116 fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
117 vcpu->arch.sve_state,
118 vcpu->arch.sve_max_vl,
119 NULL, 0, &vcpu->arch.svcr);
120
121 clear_thread_flag(TIF_FOREIGN_FPSTATE);
122 update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
123 }
124 }
125
126 /*
127 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
128 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
129 * disappears and another task or vcpu appears that recycles the same
130 * struct fpsimd_state.
131 */
kvm_arch_vcpu_put_fp(struct kvm_vcpu * vcpu)132 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
133 {
134 unsigned long flags;
135
136 local_irq_save(flags);
137
138 /*
139 * If we have VHE then the Hyp code will reset CPACR_EL1 to
140 * CPACR_EL1_DEFAULT and we need to reenable SME.
141 */
142 if (has_vhe() && system_supports_sme()) {
143 /* Also restore EL0 state seen on entry */
144 if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
145 sysreg_clear_set(CPACR_EL1, 0,
146 CPACR_EL1_SMEN_EL0EN |
147 CPACR_EL1_SMEN_EL1EN);
148 else
149 sysreg_clear_set(CPACR_EL1,
150 CPACR_EL1_SMEN_EL0EN,
151 CPACR_EL1_SMEN_EL1EN);
152 }
153
154 if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
155 if (vcpu_has_sve(vcpu)) {
156 __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
157
158 /*
159 * Restore the VL that was saved when bound to the CPU,
160 * which is the maximum VL for the guest. Because
161 * the layout of the data when saving the sve state
162 * depends on the VL, we need to use a consistent VL.
163 * Note that this means that at guest exit ZCR_EL1 is
164 * not necessarily the same as on guest entry.
165 *
166 * Flushing the cpu state sets the TIF_FOREIGN_FPSTATE
167 * bit for the context, which lets the kernel restore
168 * the sve state, including ZCR_EL1 later.
169 */
170 if (!has_vhe())
171 sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
172 SYS_ZCR_EL1);
173 }
174
175 fpsimd_save_and_flush_cpu_state();
176 } else if (has_vhe() && system_supports_sve()) {
177 /*
178 * The FPSIMD/SVE state in the CPU has not been touched, and we
179 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
180 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
181 * for EL0. To avoid spurious traps, restore the trap state
182 * seen by kvm_arch_vcpu_load_fp():
183 */
184 if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
185 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
186 else
187 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
188 }
189
190 update_thread_flag(TIF_SVE, 0);
191
192 local_irq_restore(flags);
193 }
194