arch/arm64/kvm/fpsimd.c - linux - Git at Google

 // 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 = &current->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);

 	if (!system_supports_fpsimd())
 		return;

 	fpsimd_kvm_prepare();

 	vcpu->arch.fp_state = FP_STATE_HOST_OWNED;

 	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
 	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
 		vcpu_set_flag(vcpu, 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_clear_flag(vcpu, HOST_SME_ENABLED);
 		if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
 			vcpu_set_flag(vcpu, HOST_SME_ENABLED);

 		if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
 			vcpu->arch.fp_state = FP_STATE_FREE;
 			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).
  */
 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
 {
 	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
 		vcpu->arch.fp_state = 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 (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {

 		/*
 		 * 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.za_state = NULL;
 		fp_state.svcr = &vcpu->arch.svcr;
 		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
 	 * CPACR_EL1_DEFAULT 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_EL1_SMEN_EL0EN |
 					 CPACR_EL1_SMEN_EL1EN);
 		else
 			sysreg_clear_set(CPACR_EL1,
 					 CPACR_EL1_SMEN_EL0EN,
 					 CPACR_EL1_SMEN_EL1EN);
 	}

 	if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
 		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_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);
 }
	// 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 = &current->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);

	if (!system_supports_fpsimd())
	return;

	fpsimd_kvm_prepare();

	vcpu->arch.fp_state = FP_STATE_HOST_OWNED;

	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
	vcpu_set_flag(vcpu, 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_clear_flag(vcpu, HOST_SME_ENABLED);
	if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
	vcpu_set_flag(vcpu, HOST_SME_ENABLED);

	if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK \| SVCR_ZA_MASK)) {
	vcpu->arch.fp_state = FP_STATE_FREE;
	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).
	*/
	void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
	{
	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
	vcpu->arch.fp_state = 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 (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {

	/*
	* 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.za_state = NULL;
	fp_state.svcr = &vcpu->arch.svcr;
	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
	* CPACR_EL1_DEFAULT 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_EL1_SMEN_EL0EN \|
	CPACR_EL1_SMEN_EL1EN);
	else
	sysreg_clear_set(CPACR_EL1,
	CPACR_EL1_SMEN_EL0EN,
	CPACR_EL1_SMEN_EL1EN);
	}

	if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
	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_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);
	}