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 vcpu->arch.flags &= ~KVM_ARM64_FP_ENABLED;
81 vcpu->arch.flags |= KVM_ARM64_FP_HOST;
82
83 vcpu->arch.flags &= ~KVM_ARM64_HOST_SVE_ENABLED;
84 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
85 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
86 }
87
kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu * vcpu)88 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
89 {
90 if (test_thread_flag(TIF_FOREIGN_FPSTATE))
91 vcpu->arch.flags |= KVM_ARM64_FP_FOREIGN_FPSTATE;
92 else
93 vcpu->arch.flags &= ~KVM_ARM64_FP_FOREIGN_FPSTATE;
94 }
95
96 /*
97 * If the guest FPSIMD state was loaded, update the host's context
98 * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
99 * so that they will be written back if the kernel clobbers them due to
100 * kernel-mode NEON before re-entry into the guest.
101 */
kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu * vcpu)102 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
103 {
104 WARN_ON_ONCE(!irqs_disabled());
105
106 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
107 fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
108 vcpu->arch.sve_state,
109 vcpu->arch.sve_max_vl);
110
111 clear_thread_flag(TIF_FOREIGN_FPSTATE);
112 update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
113 }
114 }
115
116 /*
117 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
118 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
119 * disappears and another task or vcpu appears that recycles the same
120 * struct fpsimd_state.
121 */
kvm_arch_vcpu_put_fp(struct kvm_vcpu * vcpu)122 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
123 {
124 unsigned long flags;
125
126 local_irq_save(flags);
127
128 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
129 if (vcpu_has_sve(vcpu)) {
130 __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
131
132 /* Restore the VL that was saved when bound to the CPU */
133 if (!has_vhe())
134 sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
135 SYS_ZCR_EL1);
136 }
137
138 fpsimd_save_and_flush_cpu_state();
139 } else if (has_vhe() && system_supports_sve()) {
140 /*
141 * The FPSIMD/SVE state in the CPU has not been touched, and we
142 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
143 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
144 * for EL0. To avoid spurious traps, restore the trap state
145 * seen by kvm_arch_vcpu_load_fp():
146 */
147 if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
148 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
149 else
150 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
151 }
152
153 update_thread_flag(TIF_SVE, 0);
154
155 local_irq_restore(flags);
156 }
157