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// SPDX-License-Identifier: GPL-2.0
/*
* arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers
*
* Copyright 2018 Arm Limited
* Author: Dave Martin <Dave.Martin@arm.com>
*/
#include <linux/irqflags.h>
#include <linux/sched.h>
#include <linux/kvm_host.h>
#include <asm/fpsimd.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_hyp.h>
#include <asm/kvm_mmu.h>
#include <asm/sysreg.h>
void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
{
struct task_struct *p = vcpu->arch.parent_task;
struct user_fpsimd_state *fpsimd;
if (!is_protected_kvm_enabled() || !p)
return;
fpsimd = &p->thread.uw.fpsimd_state;
kvm_unshare_hyp(fpsimd, fpsimd + 1);
put_task_struct(p);
}
/*
* Called on entry to KVM_RUN unless this vcpu previously ran at least
* once and the most recent prior KVM_RUN for this vcpu was called from
* the same task as current (highly likely).
*
* This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
* such that on entering hyp the relevant parts of current are already
* mapped.
*/
int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
{
int ret;
struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state;
kvm_vcpu_unshare_task_fp(vcpu);
/* Make sure the host task fpsimd state is visible to hyp: */
ret = kvm_share_hyp(fpsimd, fpsimd + 1);
if (ret)
return ret;
vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
/*
* We need to keep current's task_struct pinned until its data has been
* unshared with the hypervisor to make sure it is not re-used by the
* kernel and donated to someone else while already shared -- see
* kvm_vcpu_unshare_task_fp() for the matching put_task_struct().
*/
if (is_protected_kvm_enabled()) {
get_task_struct(current);
vcpu->arch.parent_task = current;
}
return 0;
}
/*
* Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
* The actual loading is done by the FPSIMD access trap taken to hyp.
*
* Here, we just set the correct metadata to indicate that the FPSIMD
* state in the cpu regs (if any) belongs to current on the host.
*/
void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
{
BUG_ON(!current->mm);
BUG_ON(test_thread_flag(TIF_SVE));
vcpu->arch.flags &= ~KVM_ARM64_FP_ENABLED;
vcpu->arch.flags |= KVM_ARM64_FP_HOST;
vcpu->arch.flags &= ~KVM_ARM64_HOST_SVE_ENABLED;
if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
/*
* We don't currently support SME guests but if we leave
* things in streaming mode then when the guest starts running
* FPSIMD or SVE code it may generate SME traps so as a
* special case if we are in streaming mode we force the host
* state to be saved now and exit streaming mode so that we
* don't have to handle any SME traps for valid guest
* operations. Do this for ZA as well for now for simplicity.
*/
if (system_supports_sme()) {
vcpu->arch.flags &= ~KVM_ARM64_HOST_SME_ENABLED;
if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
vcpu->arch.flags |= KVM_ARM64_HOST_SME_ENABLED;
if (read_sysreg_s(SYS_SVCR) &
(SVCR_SM_MASK | SVCR_ZA_MASK)) {
vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
fpsimd_save_and_flush_cpu_state();
}
}
}
/*
* Called just before entering the guest once we are no longer preemptable
* and interrupts are disabled. If we have managed to run anything using
* FP while we were preemptible (such as off the back of an interrupt),
* then neither the host nor the guest own the FP hardware (and it was the
* responsibility of the code that used FP to save the existing state).
*
* Note that not supporting FP is basically the same thing as far as the
* hypervisor is concerned (nothing to save).
*/
void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
{
if (!system_supports_fpsimd() || test_thread_flag(TIF_FOREIGN_FPSTATE))
vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED | KVM_ARM64_FP_HOST);
}
/*
* Called just after exiting the guest. If the guest FPSIMD state
* was loaded, update the host's context tracking data mark the CPU
* FPSIMD regs as dirty and belonging to vcpu so that they will be
* written back if the kernel clobbers them due to kernel-mode NEON
* before re-entry into the guest.
*/
void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
{
WARN_ON_ONCE(!irqs_disabled());
if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
/*
* Currently we do not support SME guests so SVCR is
* always 0 and we just need a variable to point to.
*/
fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
vcpu->arch.sve_state,
vcpu->arch.sve_max_vl,
NULL, 0, &vcpu->arch.svcr);
clear_thread_flag(TIF_FOREIGN_FPSTATE);
update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
}
}
/*
* Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
* cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
* disappears and another task or vcpu appears that recycles the same
* struct fpsimd_state.
*/
void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
{
unsigned long flags;
local_irq_save(flags);
/*
* If we have VHE then the Hyp code will reset CPACR_EL1 to
* CPACR_EL1_DEFAULT and we need to reenable SME.
*/
if (has_vhe() && system_supports_sme()) {
/* Also restore EL0 state seen on entry */
if (vcpu->arch.flags & KVM_ARM64_HOST_SME_ENABLED)
sysreg_clear_set(CPACR_EL1, 0,
CPACR_EL1_SMEN_EL0EN |
CPACR_EL1_SMEN_EL1EN);
else
sysreg_clear_set(CPACR_EL1,
CPACR_EL1_SMEN_EL0EN,
CPACR_EL1_SMEN_EL1EN);
}
if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
if (vcpu_has_sve(vcpu)) {
__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
/* Restore the VL that was saved when bound to the CPU */
if (!has_vhe())
sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
SYS_ZCR_EL1);
}
fpsimd_save_and_flush_cpu_state();
} else if (has_vhe() && system_supports_sve()) {
/*
* The FPSIMD/SVE state in the CPU has not been touched, and we
* have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
* reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
* for EL0. To avoid spurious traps, restore the trap state
* seen by kvm_arch_vcpu_load_fp():
*/
if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
else
sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
}
update_thread_flag(TIF_SVE, 0);
local_irq_restore(flags);
}
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