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