xref: /kernel/linux/linux-5.10/arch/arm64/kvm/fpsimd.c (revision 8c2ecf20) 
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 */
26int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
27{
28	int ret;
29
30	struct thread_info *ti = &current->thread_info;
31	struct user_fpsimd_state *fpsimd = &current->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);
47error:
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 */
61void 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 */
83void 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 */
103void 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