/*
 * Copyright (C) 2015 - ARM Ltd
 * Author: Marc Zyngier <marc.zyngier@arm.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/linkage.h>

#include <asm/alternative.h>
#include <asm/asm-offsets.h>
#include <asm/assembler.h>
#include <asm/fpsimdmacros.h>
#include <asm/kvm.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_mmu.h>

#define CPU_GP_REG_OFFSET(x)	(CPU_GP_REGS + x)
#define CPU_XREG_OFFSET(x)	CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)

	.text
	.pushsection	.hyp.text, "ax"

/*
 * We treat x18 as callee-saved as the host may use it as a platform
 * register (e.g. for shadow call stack).
 */
.macro save_callee_saved_regs ctxt
	str	x18,      [\ctxt, #CPU_XREG_OFFSET(18)]
	stp	x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
	stp	x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
	stp	x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
	stp	x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
	stp	x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
	stp	x29, lr,  [\ctxt, #CPU_XREG_OFFSET(29)]
.endm

.macro restore_callee_saved_regs ctxt
	// We require \ctxt is not x18-x28
	ldr	x18,      [\ctxt, #CPU_XREG_OFFSET(18)]
	ldp	x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
	ldp	x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
	ldp	x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
	ldp	x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
	ldp	x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
	ldp	x29, lr,  [\ctxt, #CPU_XREG_OFFSET(29)]
.endm

/*
 * u64 __guest_enter(struct kvm_vcpu *vcpu,
 *		     struct kvm_cpu_context *host_ctxt);
 */
ENTRY(__guest_enter)
	// x0: vcpu
	// x1: host context
	// x2-x17: clobbered by macros
	// x29: guest context

	// Store the host regs
	save_callee_saved_regs x1

	// Now the host state is stored if we have a pending RAS SError it must
	// affect the host. If any asynchronous exception is pending we defer
	// the guest entry. The DSB isn't necessary before v8.2 as any SError
	// would be fatal.
alternative_if ARM64_HAS_RAS_EXTN
	dsb	nshst
	isb
alternative_else_nop_endif
	mrs	x1, isr_el1
	cbz	x1,  1f
	mov	x0, #ARM_EXCEPTION_IRQ
	ret

1:
	add	x29, x0, #VCPU_CONTEXT

	// Restore guest regs x0-x17
	ldp	x0, x1,   [x29, #CPU_XREG_OFFSET(0)]
	ldp	x2, x3,   [x29, #CPU_XREG_OFFSET(2)]
	ldp	x4, x5,   [x29, #CPU_XREG_OFFSET(4)]
	ldp	x6, x7,   [x29, #CPU_XREG_OFFSET(6)]
	ldp	x8, x9,   [x29, #CPU_XREG_OFFSET(8)]
	ldp	x10, x11, [x29, #CPU_XREG_OFFSET(10)]
	ldp	x12, x13, [x29, #CPU_XREG_OFFSET(12)]
	ldp	x14, x15, [x29, #CPU_XREG_OFFSET(14)]
	ldp	x16, x17, [x29, #CPU_XREG_OFFSET(16)]

	// Restore guest regs x18-x29, lr
	restore_callee_saved_regs x29

	// Do not touch any register after this!
	eret
ENDPROC(__guest_enter)

ENTRY(__guest_exit)
	// x0: return code
	// x1: vcpu
	// x2-x29,lr: vcpu regs
	// vcpu x0-x1 on the stack

	add	x1, x1, #VCPU_CONTEXT

	ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)

	// Store the guest regs x2 and x3
	stp	x2, x3,   [x1, #CPU_XREG_OFFSET(2)]

	// Retrieve the guest regs x0-x1 from the stack
	ldp	x2, x3, [sp], #16	// x0, x1

	// Store the guest regs x0-x1 and x4-x17
	stp	x2, x3,   [x1, #CPU_XREG_OFFSET(0)]
	stp	x4, x5,   [x1, #CPU_XREG_OFFSET(4)]
	stp	x6, x7,   [x1, #CPU_XREG_OFFSET(6)]
	stp	x8, x9,   [x1, #CPU_XREG_OFFSET(8)]
	stp	x10, x11, [x1, #CPU_XREG_OFFSET(10)]
	stp	x12, x13, [x1, #CPU_XREG_OFFSET(12)]
	stp	x14, x15, [x1, #CPU_XREG_OFFSET(14)]
	stp	x16, x17, [x1, #CPU_XREG_OFFSET(16)]

	// Store the guest regs x18-x29, lr
	save_callee_saved_regs x1

	get_host_ctxt	x2, x3

	// Now restore the host regs
	restore_callee_saved_regs x2

alternative_if ARM64_HAS_RAS_EXTN
	// If we have the RAS extensions we can consume a pending error
	// without an unmask-SError and isb.
	esb
	mrs_s	x2, SYS_DISR_EL1
	str	x2, [x1, #(VCPU_FAULT_DISR - VCPU_CONTEXT)]
	cbz	x2, 1f
	msr_s	SYS_DISR_EL1, xzr
	orr	x0, x0, #(1<<ARM_EXIT_WITH_SERROR_BIT)
1:	ret
alternative_else
	// If we have a pending asynchronous abort, now is the
	// time to find out. From your VAXorcist book, page 666:
	// "Threaten me not, oh Evil one!  For I speak with
	// the power of DEC, and I command thee to show thyself!"
	mrs	x2, elr_el2
	mrs	x3, esr_el2
	mrs	x4, spsr_el2
	mov	x5, x0

	dsb	sy		// Synchronize against in-flight ld/st
	nop
	msr	daifclr, #4	// Unmask aborts
alternative_endif

	// This is our single instruction exception window. A pending
	// SError is guaranteed to occur at the earliest when we unmask
	// it, and at the latest just after the ISB.
abort_guest_exit_start:

	isb

abort_guest_exit_end:
	msr	daifset, #4	// Mask aborts
	ret

	_kvm_extable	abort_guest_exit_start, 9997f
	_kvm_extable	abort_guest_exit_end, 9997f
9997:
	msr	daifset, #4	// Mask aborts
	mov	x0, #(1 << ARM_EXIT_WITH_SERROR_BIT)

	// restore the EL1 exception context so that we can report some
	// information. Merge the exception code with the SError pending bit.
	msr	elr_el2, x2
	msr	esr_el2, x3
	msr	spsr_el2, x4
	orr	x0, x0, x5
1:	ret
ENDPROC(__guest_exit)