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/thread_info.h>
11 #include <linux/kvm_host.h>
12 #include <asm/fpsimd.h>
13 #include <asm/kvm_asm.h>
14 #include <asm/kvm_host.h>
15 #include <asm/kvm_mmu.h>
16 #include <asm/sysreg.h>
17
18 /*
19 * Called on entry to KVM_RUN unless this vcpu previously ran at least
20 * once and the most recent prior KVM_RUN for this vcpu was called from
21 * the same task as current (highly likely).
22 *
23 * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
24 * such that on entering hyp the relevant parts of current are already
25 * mapped.
26 */
27 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
28 {
29 int ret;
30
31 struct thread_info *ti = ¤t->thread_info;
32 struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state;
33
34 /*
35 * Make sure the host task thread flags and fpsimd state are
36 * visible to hyp:
37 */
38 ret = create_hyp_mappings(ti, ti + 1, PAGE_HYP);
39 if (ret)
40 goto error;
41
42 ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP);
43 if (ret)
44 goto error;
45
46 vcpu->arch.host_thread_info = kern_hyp_va(ti);
47 vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
48 error:
49 return ret;
50 }
51
52 /*
53 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
54 * The actual loading is done by the FPSIMD access trap taken to hyp.
55 *
56 * Here, we just set the correct metadata to indicate that the FPSIMD
57 * state in the cpu regs (if any) belongs to current on the host.
58 *
59 * TIF_SVE is backed up here, since it may get clobbered with guest state.
60 * This flag is restored by kvm_arch_vcpu_put_fp(vcpu).
61 */
62 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
63 {
64 BUG_ON(!current->mm);
65
66 vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
67 KVM_ARM64_HOST_SVE_IN_USE |
68 KVM_ARM64_HOST_SVE_ENABLED);
69 vcpu->arch.flags |= KVM_ARM64_FP_HOST;
70
71 if (test_thread_flag(TIF_SVE))
72 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE;
73
74 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
75 vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
76 }
77
78 /*
79 * If the guest FPSIMD state was loaded, update the host's context
80 * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
81 * so that they will be written back if the kernel clobbers them due to
82 * kernel-mode NEON before re-entry into the guest.
83 */
84 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
85 {
86 WARN_ON_ONCE(!irqs_disabled());
87
88 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
89 fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.gp_regs.fp_regs,
90 vcpu->arch.sve_state,
91 vcpu->arch.sve_max_vl);
92
93 clear_thread_flag(TIF_FOREIGN_FPSTATE);
94 update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
95 }
96 }
97
98 /*
99 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
100 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
101 * disappears and another task or vcpu appears that recycles the same
102 * struct fpsimd_state.
103 */
104 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
105 {
106 unsigned long flags;
107 bool host_has_sve = system_supports_sve();
108 bool guest_has_sve = vcpu_has_sve(vcpu);
109
110 local_irq_save(flags);
111
112 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
113 u64 *guest_zcr = &vcpu->arch.ctxt.sys_regs[ZCR_EL1];
114
115 fpsimd_save_and_flush_cpu_state();
116
117 if (guest_has_sve)
118 *guest_zcr = read_sysreg_s(SYS_ZCR_EL12);
119 } else if (host_has_sve) {
120 /*
121 * The FPSIMD/SVE state in the CPU has not been touched, and we
122 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
123 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
124 * for EL0. To avoid spurious traps, restore the trap state
125 * seen by kvm_arch_vcpu_load_fp():
126 */
127 if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
128 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
129 else
130 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
131 }
132
133 update_thread_flag(TIF_SVE,
134 vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE);
135
136 local_irq_restore(flags);
137 }