cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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fpsimd.c (6157B)


      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/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>
     16
     17void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
     18{
     19	struct task_struct *p = vcpu->arch.parent_task;
     20	struct user_fpsimd_state *fpsimd;
     21
     22	if (!is_protected_kvm_enabled() || !p)
     23		return;
     24
     25	fpsimd = &p->thread.uw.fpsimd_state;
     26	kvm_unshare_hyp(fpsimd, fpsimd + 1);
     27	put_task_struct(p);
     28}
     29
     30/*
     31 * Called on entry to KVM_RUN unless this vcpu previously ran at least
     32 * once and the most recent prior KVM_RUN for this vcpu was called from
     33 * the same task as current (highly likely).
     34 *
     35 * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
     36 * such that on entering hyp the relevant parts of current are already
     37 * mapped.
     38 */
     39int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
     40{
     41	int ret;
     42
     43	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
     44
     45	kvm_vcpu_unshare_task_fp(vcpu);
     46
     47	/* Make sure the host task fpsimd state is visible to hyp: */
     48	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
     49	if (ret)
     50		return ret;
     51
     52	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
     53
     54	/*
     55	 * We need to keep current's task_struct pinned until its data has been
     56	 * unshared with the hypervisor to make sure it is not re-used by the
     57	 * kernel and donated to someone else while already shared -- see
     58	 * kvm_vcpu_unshare_task_fp() for the matching put_task_struct().
     59	 */
     60	if (is_protected_kvm_enabled()) {
     61		get_task_struct(current);
     62		vcpu->arch.parent_task = current;
     63	}
     64
     65	return 0;
     66}
     67
     68/*
     69 * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
     70 * The actual loading is done by the FPSIMD access trap taken to hyp.
     71 *
     72 * Here, we just set the correct metadata to indicate that the FPSIMD
     73 * state in the cpu regs (if any) belongs to current on the host.
     74 */
     75void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
     76{
     77	BUG_ON(!current->mm);
     78	BUG_ON(test_thread_flag(TIF_SVE));
     79
     80	vcpu->arch.flags &= ~KVM_ARM64_FP_ENABLED;
     81	vcpu->arch.flags |= KVM_ARM64_FP_HOST;
     82
     83	vcpu->arch.flags &= ~KVM_ARM64_HOST_SVE_ENABLED;
     84	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
     85		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
     86
     87	/*
     88	 * We don't currently support SME guests but if we leave
     89	 * things in streaming mode then when the guest starts running
     90	 * FPSIMD or SVE code it may generate SME traps so as a
     91	 * special case if we are in streaming mode we force the host
     92	 * state to be saved now and exit streaming mode so that we
     93	 * don't have to handle any SME traps for valid guest
     94	 * operations. Do this for ZA as well for now for simplicity.
     95	 */
     96	if (system_supports_sme()) {
     97		vcpu->arch.flags &= ~KVM_ARM64_HOST_SME_ENABLED;
     98		if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
     99			vcpu->arch.flags |= KVM_ARM64_HOST_SME_ENABLED;
    100
    101		if (read_sysreg_s(SYS_SVCR) &
    102		    (SVCR_SM_MASK | SVCR_ZA_MASK)) {
    103			vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
    104			fpsimd_save_and_flush_cpu_state();
    105		}
    106	}
    107}
    108
    109/*
    110 * Called just before entering the guest once we are no longer
    111 * preemptable. Syncs the host's TIF_FOREIGN_FPSTATE with the KVM
    112 * mirror of the flag used by the hypervisor.
    113 */
    114void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
    115{
    116	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
    117		vcpu->arch.flags |= KVM_ARM64_FP_FOREIGN_FPSTATE;
    118	else
    119		vcpu->arch.flags &= ~KVM_ARM64_FP_FOREIGN_FPSTATE;
    120}
    121
    122/*
    123 * Called just after exiting the guest. If the guest FPSIMD state
    124 * was loaded, update the host's context tracking data mark the CPU
    125 * FPSIMD regs as dirty and belonging to vcpu so that they will be
    126 * written back if the kernel clobbers them due to kernel-mode NEON
    127 * before re-entry into the guest.
    128 */
    129void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
    130{
    131	WARN_ON_ONCE(!irqs_disabled());
    132
    133	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
    134		/*
    135		 * Currently we do not support SME guests so SVCR is
    136		 * always 0 and we just need a variable to point to.
    137		 */
    138		fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
    139					 vcpu->arch.sve_state,
    140					 vcpu->arch.sve_max_vl,
    141					 NULL, 0, &vcpu->arch.svcr);
    142
    143		clear_thread_flag(TIF_FOREIGN_FPSTATE);
    144		update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
    145	}
    146}
    147
    148/*
    149 * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
    150 * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
    151 * disappears and another task or vcpu appears that recycles the same
    152 * struct fpsimd_state.
    153 */
    154void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
    155{
    156	unsigned long flags;
    157
    158	local_irq_save(flags);
    159
    160	/*
    161	 * If we have VHE then the Hyp code will reset CPACR_EL1 to
    162	 * CPACR_EL1_DEFAULT and we need to reenable SME.
    163	 */
    164	if (has_vhe() && system_supports_sme()) {
    165		/* Also restore EL0 state seen on entry */
    166		if (vcpu->arch.flags & KVM_ARM64_HOST_SME_ENABLED)
    167			sysreg_clear_set(CPACR_EL1, 0,
    168					 CPACR_EL1_SMEN_EL0EN |
    169					 CPACR_EL1_SMEN_EL1EN);
    170		else
    171			sysreg_clear_set(CPACR_EL1,
    172					 CPACR_EL1_SMEN_EL0EN,
    173					 CPACR_EL1_SMEN_EL1EN);
    174	}
    175
    176	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
    177		if (vcpu_has_sve(vcpu)) {
    178			__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
    179
    180			/* Restore the VL that was saved when bound to the CPU */
    181			if (!has_vhe())
    182				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
    183						       SYS_ZCR_EL1);
    184		}
    185
    186		fpsimd_save_and_flush_cpu_state();
    187	} else if (has_vhe() && system_supports_sve()) {
    188		/*
    189		 * The FPSIMD/SVE state in the CPU has not been touched, and we
    190		 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
    191		 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
    192		 * for EL0.  To avoid spurious traps, restore the trap state
    193		 * seen by kvm_arch_vcpu_load_fp():
    194		 */
    195		if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
    196			sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
    197		else
    198			sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
    199	}
    200
    201	update_thread_flag(TIF_SVE, 0);
    202
    203	local_irq_restore(flags);
    204}