1 // SPDX-License-Identifier: GPL-2.0
3 * arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers
5 * Copyright 2018 Arm Limited
6 * Author: Dave Martin <Dave.Martin@arm.com>
8 #include <linux/irqflags.h>
9 #include <linux/sched.h>
10 #include <linux/kvm_host.h>
11 #include <asm/fpsimd.h>
12 #include <asm/kvm_asm.h>
13 #include <asm/kvm_hyp.h>
14 #include <asm/kvm_mmu.h>
15 #include <asm/sysreg.h>
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).
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
26 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
28 struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state;
31 /* pKVM has its own tracking of the host fpsimd state. */
32 if (is_protected_kvm_enabled())
35 /* Make sure the host task fpsimd state is visible to hyp: */
36 ret = kvm_share_hyp(fpsimd, fpsimd + 1);
44 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
45 * The actual loading is done by the FPSIMD access trap taken to hyp.
47 * Here, we just set the correct metadata to indicate that the FPSIMD
48 * state in the cpu regs (if any) belongs to current on the host.
50 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
54 if (!system_supports_fpsimd())
60 * We will check TIF_FOREIGN_FPSTATE just before entering the
61 * guest in kvm_arch_vcpu_ctxflush_fp() and override this to
62 * FP_STATE_FREE if the flag set.
64 *host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED;
65 *host_data_ptr(fpsimd_state) = kern_hyp_va(¤t->thread.uw.fpsimd_state);
67 vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
68 if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
69 vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
71 if (system_supports_sme()) {
72 vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
73 if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
74 vcpu_set_flag(vcpu, HOST_SME_ENABLED);
77 * If PSTATE.SM is enabled then save any pending FP
78 * state and disable PSTATE.SM. If we leave PSTATE.SM
79 * enabled and the guest does not enable SME via
80 * CPACR_EL1.SMEN then operations that should be valid
81 * may generate SME traps from EL1 to EL1 which we
82 * can't intercept and which would confuse the guest.
84 * Do the same for PSTATE.ZA in the case where there
85 * is state in the registers which has not already
86 * been saved, this is very unlikely to happen.
88 if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
89 *host_data_ptr(fp_owner) = FP_STATE_FREE;
90 fpsimd_save_and_flush_cpu_state();
95 * If normal guests gain SME support, maintain this behavior for pKVM
96 * guests, which don't support SME.
98 WARN_ON(is_protected_kvm_enabled() && system_supports_sme() &&
99 read_sysreg_s(SYS_SVCR));
103 * Called just before entering the guest once we are no longer preemptible
104 * and interrupts are disabled. If we have managed to run anything using
105 * FP while we were preemptible (such as off the back of an interrupt),
106 * then neither the host nor the guest own the FP hardware (and it was the
107 * responsibility of the code that used FP to save the existing state).
109 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
111 if (test_thread_flag(TIF_FOREIGN_FPSTATE))
112 *host_data_ptr(fp_owner) = FP_STATE_FREE;
116 * Called just after exiting the guest. If the guest FPSIMD state
117 * was loaded, update the host's context tracking data mark the CPU
118 * FPSIMD regs as dirty and belonging to vcpu so that they will be
119 * written back if the kernel clobbers them due to kernel-mode NEON
120 * before re-entry into the guest.
122 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
124 struct cpu_fp_state fp_state;
126 WARN_ON_ONCE(!irqs_disabled());
128 if (guest_owns_fp_regs()) {
130 * Currently we do not support SME guests so SVCR is
131 * always 0 and we just need a variable to point to.
133 fp_state.st = &vcpu->arch.ctxt.fp_regs;
134 fp_state.sve_state = vcpu->arch.sve_state;
135 fp_state.sve_vl = vcpu->arch.sve_max_vl;
136 fp_state.sme_state = NULL;
137 fp_state.svcr = &vcpu->arch.svcr;
138 fp_state.fpmr = &vcpu->arch.fpmr;
139 fp_state.fp_type = &vcpu->arch.fp_type;
141 if (vcpu_has_sve(vcpu))
142 fp_state.to_save = FP_STATE_SVE;
144 fp_state.to_save = FP_STATE_FPSIMD;
146 fpsimd_bind_state_to_cpu(&fp_state);
148 clear_thread_flag(TIF_FOREIGN_FPSTATE);
153 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
154 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
155 * disappears and another task or vcpu appears that recycles the same
156 * struct fpsimd_state.
158 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
162 local_irq_save(flags);
165 * If we have VHE then the Hyp code will reset CPACR_EL1 to
166 * the default value and we need to reenable SME.
168 if (has_vhe() && system_supports_sme()) {
169 /* Also restore EL0 state seen on entry */
170 if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
171 sysreg_clear_set(CPACR_EL1, 0, CPACR_ELx_SMEN);
173 sysreg_clear_set(CPACR_EL1,
174 CPACR_EL1_SMEN_EL0EN,
175 CPACR_EL1_SMEN_EL1EN);
179 if (guest_owns_fp_regs()) {
180 if (vcpu_has_sve(vcpu)) {
181 u64 zcr = read_sysreg_el1(SYS_ZCR);
184 * If the vCPU is in the hyp context then ZCR_EL1 is
185 * loaded with its vEL2 counterpart.
187 __vcpu_sys_reg(vcpu, vcpu_sve_zcr_elx(vcpu)) = zcr;
190 * Restore the VL that was saved when bound to the CPU,
191 * which is the maximum VL for the guest. Because the
192 * layout of the data when saving the sve state depends
193 * on the VL, we need to use a consistent (i.e., the
195 * Note that this means that at guest exit ZCR_EL1 is
196 * not necessarily the same as on guest entry.
198 * ZCR_EL2 holds the guest hypervisor's VL when running
199 * a nested guest, which could be smaller than the
200 * max for the vCPU. Similar to above, we first need to
201 * switch to a VL consistent with the layout of the
202 * vCPU's SVE state. KVM support for NV implies VHE, so
203 * using the ZCR_EL1 alias is safe.
205 if (!has_vhe() || (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)))
206 sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
211 * Flush (save and invalidate) the fpsimd/sve state so that if
212 * the host tries to use fpsimd/sve, it's not using stale data
215 * Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the
216 * context unconditionally, in both nVHE and VHE. This allows
217 * the kernel to restore the fpsimd/sve state, including ZCR_EL1
220 fpsimd_save_and_flush_cpu_state();
221 } else if (has_vhe() && system_supports_sve()) {
223 * The FPSIMD/SVE state in the CPU has not been touched, and we
224 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
225 * reset by kvm_reset_cptr_el2() in the Hyp code, disabling SVE
226 * for EL0. To avoid spurious traps, restore the trap state
227 * seen by kvm_arch_vcpu_load_fp():
229 if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
230 sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
232 sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
235 local_irq_restore(flags);