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/kvm_asm.h>
13 #include <asm/kvm_host.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.gp_regs.fp_regs);
89 clear_thread_flag(TIF_FOREIGN_FPSTATE);
90 clear_thread_flag(TIF_SVE);
91 }
92 }
93
94 /*
95 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
96 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
97 * disappears and another task or vcpu appears that recycles the same
98 * struct fpsimd_state.
99 */
kvm_arch_vcpu_put_fp(struct kvm_vcpu * vcpu)100 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
101 {
102 unsigned long flags;
103
104 local_irq_save(flags);
105
106 if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
107 /* Clean guest FP state to memory and invalidate cpu view */
108 fpsimd_save();
109 fpsimd_flush_cpu_state();
110 } else if (system_supports_sve()) {
111 /*
112 * The FPSIMD/SVE state in the CPU has not been touched, and we
113 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
114 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
115 * for EL0. To avoid spurious traps, restore the trap state
116 * seen by kvm_arch_vcpu_load_fp():
117 */
118 if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
119 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
120 else
121 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
122 }
123
124 update_thread_flag(TIF_SVE,
125 vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE);
126
127 local_irq_restore(flags);
128 }
129
