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_hyp.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  */
kvm_arch_vcpu_run_map_fp(struct kvm_vcpu * vcpu)27 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
28 {
29 	int ret;
30 
31 	struct thread_info *ti = &current->thread_info;
32 	struct user_fpsimd_state *fpsimd = &current->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 	if (vcpu->arch.sve_state) {
47 		void *sve_end;
48 
49 		sve_end = vcpu->arch.sve_state + vcpu_sve_state_size(vcpu);
50 
51 		ret = create_hyp_mappings(vcpu->arch.sve_state, sve_end,
52 					  PAGE_HYP);
53 		if (ret)
54 			goto error;
55 	}
56 
57 	vcpu->arch.host_thread_info = kern_hyp_va(ti);
58 	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
59 error:
60 	return ret;
61 }
62 
63 /*
64  * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
65  * The actual loading is done by the FPSIMD access trap taken to hyp.
66  *
67  * Here, we just set the correct metadata to indicate that the FPSIMD
68  * state in the cpu regs (if any) belongs to current on the host.
69  *
70  * TIF_SVE is backed up here, since it may get clobbered with guest state.
71  * This flag is restored by kvm_arch_vcpu_put_fp(vcpu).
72  */
kvm_arch_vcpu_load_fp(struct kvm_vcpu * vcpu)73 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
74 {
75 	BUG_ON(!current->mm);
76 
77 	vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
78 			      KVM_ARM64_HOST_SVE_IN_USE |
79 			      KVM_ARM64_HOST_SVE_ENABLED);
80 	vcpu->arch.flags |= KVM_ARM64_FP_HOST;
81 
82 	if (test_thread_flag(TIF_SVE))
83 		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE;
84 
85 	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
86 		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
87 }
88 
89 /*
90  * If the guest FPSIMD state was loaded, update the host's context
91  * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
92  * so that they will be written back if the kernel clobbers them due to
93  * kernel-mode NEON before re-entry into the guest.
94  */
kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu * vcpu)95 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
96 {
97 	WARN_ON_ONCE(!irqs_disabled());
98 
99 	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
100 		fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
101 					 vcpu->arch.sve_state,
102 					 vcpu->arch.sve_max_vl);
103 
104 		clear_thread_flag(TIF_FOREIGN_FPSTATE);
105 		update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
106 	}
107 }
108 
109 /*
110  * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
111  * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
112  * disappears and another task or vcpu appears that recycles the same
113  * struct fpsimd_state.
114  */
kvm_arch_vcpu_put_fp(struct kvm_vcpu * vcpu)115 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
116 {
117 	unsigned long flags;
118 	bool host_has_sve = system_supports_sve();
119 	bool guest_has_sve = vcpu_has_sve(vcpu);
120 
121 	local_irq_save(flags);
122 
123 	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
124 		if (guest_has_sve) {
125 			__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
126 
127 			/* Restore the VL that was saved when bound to the CPU */
128 			if (!has_vhe())
129 				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
130 						       SYS_ZCR_EL1);
131 		}
132 
133 		fpsimd_save_and_flush_cpu_state();
134 	} else if (has_vhe() && host_has_sve) {
135 		/*
136 		 * The FPSIMD/SVE state in the CPU has not been touched, and we
137 		 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
138 		 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
139 		 * for EL0.  To avoid spurious traps, restore the trap state
140 		 * seen by kvm_arch_vcpu_load_fp():
141 		 */
142 		if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
143 			sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
144 		else
145 			sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
146 	}
147 
148 	update_thread_flag(TIF_SVE,
149 			   vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE);
150 
151 	local_irq_restore(flags);
152 }
153