arch/arm64/kvm/hyp/include/hyp/switch.h

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2015 - ARM Ltd
 * Author: Marc Zyngier <marc.zyngier@arm.com>
 */

#ifndef __ARM64_KVM_HYP_SWITCH_H__
#define __ARM64_KVM_HYP_SWITCH_H__

#include <hyp/adjust_pc.h>

#include <linux/arm-smccc.h>
#include <linux/kvm_host.h>
#include <linux/types.h>
#include <linux/jump_label.h>
#include <uapi/linux/psci.h>

#include <kvm/arm_psci.h>

#include <asm/barrier.h>
#include <asm/cpufeature.h>
#include <asm/extable.h>
#include <asm/kprobes.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_hyp.h>
#include <asm/kvm_mmu.h>
#include <asm/fpsimd.h>
#include <asm/debug-monitors.h>
#include <asm/processor.h>
#include <asm/thread_info.h>

extern const char __hyp_panic_string[];

extern struct exception_table_entry __start___kvm_ex_table;
extern struct exception_table_entry __stop___kvm_ex_table;

/* Check whether the FP regs were dirtied while in the host-side run loop: */
static inline bool update_fp_enabled(struct kvm_vcpu *vcpu)
{
	/*
	 * When the system doesn't support FP/SIMD, we cannot rely on
	 * the _TIF_FOREIGN_FPSTATE flag. However, we always inject an
	 * abort on the very first access to FP and thus we should never
	 * see KVM_ARM64_FP_ENABLED. For added safety, make sure we always
	 * trap the accesses.
	 */
	if (!system_supports_fpsimd() ||
	    vcpu->arch.host_thread_info->flags & _TIF_FOREIGN_FPSTATE)
		vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
				      KVM_ARM64_FP_HOST);

	return !!(vcpu->arch.flags & KVM_ARM64_FP_ENABLED);
}

/* Save the 32-bit only FPSIMD system register state */
static inline void __fpsimd_save_fpexc32(struct kvm_vcpu *vcpu)
{
	if (!vcpu_el1_is_32bit(vcpu))
		return;

	__vcpu_sys_reg(vcpu, FPEXC32_EL2) = read_sysreg(fpexc32_el2);
}

static inline void __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
{
	/*
	 * We are about to set CPTR_EL2.TFP to trap all floating point
	 * register accesses to EL2, however, the ARM ARM clearly states that
	 * traps are only taken to EL2 if the operation would not otherwise
	 * trap to EL1.  Therefore, always make sure that for 32-bit guests,
	 * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
	 * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
	 * it will cause an exception.
	 */
	if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd()) {
		write_sysreg(1 << 30, fpexc32_el2);
		isb();
	}
}

static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
{
	/* Trap on AArch32 cp15 c15 (impdef sysregs) accesses (EL1 or EL0) */
	write_sysreg(1 << 15, hstr_el2);

	/*
	 * Make sure we trap PMU access from EL0 to EL2. Also sanitize
	 * PMSELR_EL0 to make sure it never contains the cycle
	 * counter, which could make a PMXEVCNTR_EL0 access UNDEF at
	 * EL1 instead of being trapped to EL2.
	 */
	write_sysreg(0, pmselr_el0);
	write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
}

static inline void __deactivate_traps_common(void)
{
	write_sysreg(0, hstr_el2);
	write_sysreg(0, pmuserenr_el0);
}

static inline void ___activate_traps(struct kvm_vcpu *vcpu)
{
	u64 hcr = vcpu->arch.hcr_el2;

	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM))
		hcr |= HCR_TVM;

	write_sysreg(hcr, hcr_el2);

	if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
		write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);
}

static inline void ___deactivate_traps(struct kvm_vcpu *vcpu)
{
	/*
	 * If we pended a virtual abort, preserve it until it gets
	 * cleared. See D1.14.3 (Virtual Interrupts) for details, but
	 * the crucial bit is "On taking a vSError interrupt,
	 * HCR_EL2.VSE is cleared to 0."
	 */
	if (vcpu->arch.hcr_el2 & HCR_VSE) {
		vcpu->arch.hcr_el2 &= ~HCR_VSE;
		vcpu->arch.hcr_el2 |= read_sysreg(hcr_el2) & HCR_VSE;
	}
}

static inline bool __translate_far_to_hpfar(u64 far, u64 *hpfar)
{
	u64 par, tmp;

	/*
	 * Resolve the IPA the hard way using the guest VA.
	 *
	 * Stage-1 translation already validated the memory access
	 * rights. As such, we can use the EL1 translation regime, and
	 * don't have to distinguish between EL0 and EL1 access.
	 *
	 * We do need to save/restore PAR_EL1 though, as we haven't
	 * saved the guest context yet, and we may return early...
	 */
	par = read_sysreg_par();
	if (!__kvm_at("s1e1r", far))
		tmp = read_sysreg_par();
	else
		tmp = SYS_PAR_EL1_F; /* back to the guest */
	write_sysreg(par, par_el1);

	if (unlikely(tmp & SYS_PAR_EL1_F))
		return false; /* Translation failed, back to guest */

	/* Convert PAR to HPFAR format */
	*hpfar = PAR_TO_HPFAR(tmp);
	return true;
}

static inline bool __populate_fault_info(struct kvm_vcpu *vcpu)
{
	u8 ec;
	u64 esr;
	u64 hpfar, far;

	esr = vcpu->arch.fault.esr_el2;
	ec = ESR_ELx_EC(esr);

	if (ec != ESR_ELx_EC_DABT_LOW && ec != ESR_ELx_EC_IABT_LOW)
		return true;

	far = read_sysreg_el2(SYS_FAR);

	/*
	 * The HPFAR can be invalid if the stage 2 fault did not
	 * happen during a stage 1 page table walk (the ESR_EL2.S1PTW
	 * bit is clear) and one of the two following cases are true:
	 *   1. The fault was due to a permission fault
	 *   2. The processor carries errata 834220
	 *
	 * Therefore, for all non S1PTW faults where we either have a
	 * permission fault or the errata workaround is enabled, we
	 * resolve the IPA using the AT instruction.
	 */
	if (!(esr & ESR_ELx_S1PTW) &&
	    (cpus_have_final_cap(ARM64_WORKAROUND_834220) ||
	     (esr & ESR_ELx_FSC_TYPE) == FSC_PERM)) {
		if (!__translate_far_to_hpfar(far, &hpfar))
			return false;
	} else {
		hpfar = read_sysreg(hpfar_el2);
	}

	vcpu->arch.fault.far_el2 = far;
	vcpu->arch.fault.hpfar_el2 = hpfar;
	return true;
}

/* Check for an FPSIMD/SVE trap and handle as appropriate */
static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
{
	bool vhe, sve_guest, sve_host;
	u8 esr_ec;

	if (!system_supports_fpsimd())
		return false;

	/*
	 * Currently system_supports_sve() currently implies has_vhe(),
	 * so the check is redundant. However, has_vhe() can be determined
	 * statically and helps the compiler remove dead code.
	 */
	if (has_vhe() && system_supports_sve()) {
		sve_guest = vcpu_has_sve(vcpu);
		sve_host = vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE;
		vhe = true;
	} else {
		sve_guest = false;
		sve_host = false;
		vhe = has_vhe();
	}

	esr_ec = kvm_vcpu_trap_get_class(vcpu);
	if (esr_ec != ESR_ELx_EC_FP_ASIMD &&
	    esr_ec != ESR_ELx_EC_SVE)
		return false;

	/* Don't handle SVE traps for non-SVE vcpus here: */
	if (!sve_guest)
		if (esr_ec != ESR_ELx_EC_FP_ASIMD)
			return false;

	/* Valid trap.  Switch the context: */

	if (vhe) {
		u64 reg = read_sysreg(cpacr_el1) | CPACR_EL1_FPEN;

		if (sve_guest)
			reg |= CPACR_EL1_ZEN;

		write_sysreg(reg, cpacr_el1);
	} else {
		write_sysreg(read_sysreg(cptr_el2) & ~(u64)CPTR_EL2_TFP,
			     cptr_el2);
	}

	isb();

	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
		/*
		 * In the SVE case, VHE is assumed: it is enforced by
		 * Kconfig and kvm_arch_init().
		 */
		if (sve_host) {
			struct thread_struct *thread = container_of(
				vcpu->arch.host_fpsimd_state,
				struct thread_struct, uw.fpsimd_state);

			sve_save_state(sve_pffr(thread),
				       &vcpu->arch.host_fpsimd_state->fpsr);
		} else {
			__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
		}

		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
	}

	if (sve_guest) {
		sve_load_state(vcpu_sve_pffr(vcpu),
			       &vcpu->arch.ctxt.fp_regs.fpsr,
			       sve_vq_from_vl(vcpu->arch.sve_max_vl) - 1);
		write_sysreg_s(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR_EL12);
	} else {
		__fpsimd_restore_state(&vcpu->arch.ctxt.fp_regs);
	}

	/* Skip restoring fpexc32 for AArch64 guests */
	if (!(read_sysreg(hcr_el2) & HCR_RW))
		write_sysreg(__vcpu_sys_reg(vcpu, FPEXC32_EL2), fpexc32_el2);

	vcpu->arch.flags |= KVM_ARM64_FP_ENABLED;

	return true;
}

static inline bool handle_tx2_tvm(struct kvm_vcpu *vcpu)
{
	u32 sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));
	int rt = kvm_vcpu_sys_get_rt(vcpu);
	u64 val = vcpu_get_reg(vcpu, rt);

	/*
	 * The normal sysreg handling code expects to see the traps,
	 * let's not do anything here.
	 */
	if (vcpu->arch.hcr_el2 & HCR_TVM)
		return false;

	switch (sysreg) {
	case SYS_SCTLR_EL1:
		write_sysreg_el1(val, SYS_SCTLR);
		break;
	case SYS_TTBR0_EL1:
		write_sysreg_el1(val, SYS_TTBR0);
		break;
	case SYS_TTBR1_EL1:
		write_sysreg_el1(val, SYS_TTBR1);
		break;
	case SYS_TCR_EL1:
		write_sysreg_el1(val, SYS_TCR);
		break;
	case SYS_ESR_EL1:
		write_sysreg_el1(val, SYS_ESR);
		break;
	case SYS_FAR_EL1:
		write_sysreg_el1(val, SYS_FAR);
		break;
	case SYS_AFSR0_EL1:
		write_sysreg_el1(val, SYS_AFSR0);
		break;
	case SYS_AFSR1_EL1:
		write_sysreg_el1(val, SYS_AFSR1);
		break;
	case SYS_MAIR_EL1:
		write_sysreg_el1(val, SYS_MAIR);
		break;
	case SYS_AMAIR_EL1:
		write_sysreg_el1(val, SYS_AMAIR);
		break;
	case SYS_CONTEXTIDR_EL1:
		write_sysreg_el1(val, SYS_CONTEXTIDR);
		break;
	default:
		return false;
	}

	__kvm_skip_instr(vcpu);
	return true;
}

static inline bool esr_is_ptrauth_trap(u32 esr)
{
	u32 ec = ESR_ELx_EC(esr);

	if (ec == ESR_ELx_EC_PAC)
		return true;

	if (ec != ESR_ELx_EC_SYS64)
		return false;

	switch (esr_sys64_to_sysreg(esr)) {
	case SYS_APIAKEYLO_EL1:
	case SYS_APIAKEYHI_EL1:
	case SYS_APIBKEYLO_EL1:
	case SYS_APIBKEYHI_EL1:
	case SYS_APDAKEYLO_EL1:
	case SYS_APDAKEYHI_EL1:
	case SYS_APDBKEYLO_EL1:
	case SYS_APDBKEYHI_EL1:
	case SYS_APGAKEYLO_EL1:
	case SYS_APGAKEYHI_EL1:
		return true;
	}

	return false;
}

#define __ptrauth_save_key(ctxt, key)					\
	do {								\
	u64 __val;                                                      \
	__val = read_sysreg_s(SYS_ ## key ## KEYLO_EL1);                \
	ctxt_sys_reg(ctxt, key ## KEYLO_EL1) = __val;                   \
	__val = read_sysreg_s(SYS_ ## key ## KEYHI_EL1);                \
	ctxt_sys_reg(ctxt, key ## KEYHI_EL1) = __val;                   \
} while(0)

DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);

static inline bool __hyp_handle_ptrauth(struct kvm_vcpu *vcpu)
{
	struct kvm_cpu_context *ctxt;
	u64 val;

	if (!vcpu_has_ptrauth(vcpu) ||
	    !esr_is_ptrauth_trap(kvm_vcpu_get_esr(vcpu)))
		return false;

	ctxt = this_cpu_ptr(&kvm_hyp_ctxt);
	__ptrauth_save_key(ctxt, APIA);
	__ptrauth_save_key(ctxt, APIB);
	__ptrauth_save_key(ctxt, APDA);
	__ptrauth_save_key(ctxt, APDB);
	__ptrauth_save_key(ctxt, APGA);

	vcpu_ptrauth_enable(vcpu);

	val = read_sysreg(hcr_el2);
	val |= (HCR_API | HCR_APK);
	write_sysreg(val, hcr_el2);

	return true;
}

/*
 * Return true when we were able to fixup the guest exit and should return to
 * the guest, false when we should restore the host state and return to the
 * main run loop.
 */
static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
{
	if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ)
		vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR);

	if (ARM_SERROR_PENDING(*exit_code)) {
		u8 esr_ec = kvm_vcpu_trap_get_class(vcpu);

		/*
		 * HVC already have an adjusted PC, which we need to
		 * correct in order to return to after having injected
		 * the SError.
		 *
		 * SMC, on the other hand, is *trapped*, meaning its
		 * preferred return address is the SMC itself.
		 */
		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64)
			write_sysreg_el2(read_sysreg_el2(SYS_ELR) - 4, SYS_ELR);
	}

	/*
	 * We're using the raw exception code in order to only process
	 * the trap if no SError is pending. We will come back to the
	 * same PC once the SError has been injected, and replay the
	 * trapping instruction.
	 */
	if (*exit_code != ARM_EXCEPTION_TRAP)
		goto exit;

	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM) &&
	    kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 &&
	    handle_tx2_tvm(vcpu))
		goto guest;

	/*
	 * We trap the first access to the FP/SIMD to save the host context
	 * and restore the guest context lazily.
	 * If FP/SIMD is not implemented, handle the trap and inject an
	 * undefined instruction exception to the guest.
	 * Similarly for trapped SVE accesses.
	 */
	if (__hyp_handle_fpsimd(vcpu))
		goto guest;

	if (__hyp_handle_ptrauth(vcpu))
		goto guest;

	if (!__populate_fault_info(vcpu))
		goto guest;

	if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
		bool valid;

		valid = kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_DABT_LOW &&
			kvm_vcpu_trap_get_fault_type(vcpu) == FSC_FAULT &&
			kvm_vcpu_dabt_isvalid(vcpu) &&
			!kvm_vcpu_abt_issea(vcpu) &&
			!kvm_vcpu_abt_iss1tw(vcpu);

		if (valid) {
			int ret = __vgic_v2_perform_cpuif_access(vcpu);

			if (ret == 1)
				goto guest;

			/* Promote an illegal access to an SError.*/
			if (ret == -1)
				*exit_code = ARM_EXCEPTION_EL1_SERROR;

			goto exit;
		}
	}

	if (static_branch_unlikely(&vgic_v3_cpuif_trap) &&
	    (kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 ||
	     kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_CP15_32)) {
		int ret = __vgic_v3_perform_cpuif_access(vcpu);

		if (ret == 1)
			goto guest;
	}

exit:
	/* Return to the host kernel and handle the exit */
	return false;

guest:
	/* Re-enter the guest */
	asm(ALTERNATIVE("nop", "dmb sy", ARM64_WORKAROUND_1508412));
	return true;
}

static inline void __kvm_unexpected_el2_exception(void)
{
	extern char __guest_exit_panic[];
	unsigned long addr, fixup;
	struct exception_table_entry *entry, *end;
	unsigned long elr_el2 = read_sysreg(elr_el2);

	entry = hyp_symbol_addr(__start___kvm_ex_table);
	end = hyp_symbol_addr(__stop___kvm_ex_table);

	while (entry < end) {
		addr = (unsigned long)&entry->insn + entry->insn;
		fixup = (unsigned long)&entry->fixup + entry->fixup;

		if (addr != elr_el2) {
			entry++;
			continue;
		}

		write_sysreg(fixup, elr_el2);
		return;
	}

	/* Trigger a panic after restoring the hyp context. */
	write_sysreg(__guest_exit_panic, elr_el2);
}

#endif /* __ARM64_KVM_HYP_SWITCH_H__ */