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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>
/*
* 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)
{
struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state;
int ret;
/* pKVM has its own tracking of the host fpsimd state. */
if (is_protected_kvm_enabled())
return 0;
/* Make sure the host task fpsimd state is visible to hyp: */
ret = kvm_share_hyp(fpsimd, fpsimd + 1);
if (ret)
return ret;
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);
if (!system_supports_fpsimd())
return;
fpsimd_kvm_prepare();
/*
* We will check TIF_FOREIGN_FPSTATE just before entering the
* guest in kvm_arch_vcpu_ctxflush_fp() and override this to
* FP_STATE_FREE if the flag set.
*/
*host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED;
*host_data_ptr(fpsimd_state) = kern_hyp_va(¤t->thread.uw.fpsimd_state);
vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
if (system_supports_sme()) {
vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
vcpu_set_flag(vcpu, HOST_SME_ENABLED);
/*
* If PSTATE.SM is enabled then save any pending FP
* state and disable PSTATE.SM. If we leave PSTATE.SM
* enabled and the guest does not enable SME via
* CPACR_EL1.SMEN then operations that should be valid
* may generate SME traps from EL1 to EL1 which we
* can't intercept and which would confuse the guest.
*
* Do the same for PSTATE.ZA in the case where there
* is state in the registers which has not already
* been saved, this is very unlikely to happen.
*/
if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
*host_data_ptr(fp_owner) = FP_STATE_FREE;
fpsimd_save_and_flush_cpu_state();
}
}
/*
* If normal guests gain SME support, maintain this behavior for pKVM
* guests, which don't support SME.
*/
WARN_ON(is_protected_kvm_enabled() && system_supports_sme() &&
read_sysreg_s(SYS_SVCR));
}
/*
* Called just before entering the guest once we are no longer preemptible
* 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).
*/
void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
{
if (test_thread_flag(TIF_FOREIGN_FPSTATE))
*host_data_ptr(fp_owner) = FP_STATE_FREE;
}
/*
* 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)
{
struct cpu_fp_state fp_state;
WARN_ON_ONCE(!irqs_disabled());
if (guest_owns_fp_regs()) {
/*
* Currently we do not support SME guests so SVCR is
* always 0 and we just need a variable to point to.
*/
fp_state.st = &vcpu->arch.ctxt.fp_regs;
fp_state.sve_state = vcpu->arch.sve_state;
fp_state.sve_vl = vcpu->arch.sve_max_vl;
fp_state.sme_state = NULL;
fp_state.svcr = &vcpu->arch.svcr;
fp_state.fpmr = &vcpu->arch.fpmr;
fp_state.fp_type = &vcpu->arch.fp_type;
if (vcpu_has_sve(vcpu))
fp_state.to_save = FP_STATE_SVE;
else
fp_state.to_save = FP_STATE_FPSIMD;
fpsimd_bind_state_to_cpu(&fp_state);
clear_thread_flag(TIF_FOREIGN_FPSTATE);
}
}
/*
* 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
* the default value and we need to reenable SME.
*/
if (has_vhe() && system_supports_sme()) {
/* Also restore EL0 state seen on entry */
if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
sysreg_clear_set(CPACR_EL1, 0, CPACR_ELx_SMEN);
else
sysreg_clear_set(CPACR_EL1,
CPACR_EL1_SMEN_EL0EN,
CPACR_EL1_SMEN_EL1EN);
isb();
}
if (guest_owns_fp_regs()) {
if (vcpu_has_sve(vcpu)) {
u64 zcr = read_sysreg_el1(SYS_ZCR);
/*
* If the vCPU is in the hyp context then ZCR_EL1 is
* loaded with its vEL2 counterpart.
*/
__vcpu_sys_reg(vcpu, vcpu_sve_zcr_elx(vcpu)) = zcr;
/*
* Restore the VL that was saved when bound to the CPU,
* which is the maximum VL for the guest. Because the
* layout of the data when saving the sve state depends
* on the VL, we need to use a consistent (i.e., the
* maximum) VL.
* Note that this means that at guest exit ZCR_EL1 is
* not necessarily the same as on guest entry.
*
* ZCR_EL2 holds the guest hypervisor's VL when running
* a nested guest, which could be smaller than the
* max for the vCPU. Similar to above, we first need to
* switch to a VL consistent with the layout of the
* vCPU's SVE state. KVM support for NV implies VHE, so
* using the ZCR_EL1 alias is safe.
*/
if (!has_vhe() || (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)))
sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
SYS_ZCR_EL1);
}
/*
* Flush (save and invalidate) the fpsimd/sve state so that if
* the host tries to use fpsimd/sve, it's not using stale data
* from the guest.
*
* Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the
* context unconditionally, in both nVHE and VHE. This allows
* the kernel to restore the fpsimd/sve state, including ZCR_EL1
* when needed.
*/
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 by kvm_reset_cptr_el2() in the Hyp code, disabling SVE
* for EL0. To avoid spurious traps, restore the trap state
* seen by kvm_arch_vcpu_load_fp():
*/
if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
else
sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
}
local_irq_restore(flags);
}
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