arch/arm/kvm/interrupts.S

/*
 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
 * Author: Christoffer Dall <c.dall@virtualopensystems.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, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#include <linux/linkage.h>
#include <linux/const.h>
#include <asm/unified.h>
#include <asm/page.h>
#include <asm/ptrace.h>
#include <asm/asm-offsets.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_arm.h>
#include <asm/vfpmacros.h>
#include "interrupts_head.S"

	.text

__kvm_hyp_code_start:
	.globl __kvm_hyp_code_start

/********************************************************************
 * Flush per-VMID TLBs
 *
 * void __kvm_tlb_flush_vmid(struct kvm *kvm);
 *
 * We rely on the hardware to broadcast the TLB invalidation to all CPUs
 * inside the inner-shareable domain (which is the case for all v7
 * implementations).  If we come across a non-IS SMP implementation, we'll
 * have to use an IPI based mechanism. Until then, we stick to the simple
 * hardware assisted version.
 */
ENTRY(__kvm_tlb_flush_vmid)
	push	{r2, r3}

	add	r0, r0, #KVM_VTTBR
	ldrd	r2, r3, [r0]
	mcrr	p15, 6, r2, r3, c2	@ Write VTTBR
	isb
	mcr     p15, 0, r0, c8, c3, 0	@ TLBIALLIS (rt ignored)
	dsb
	isb
	mov	r2, #0
	mov	r3, #0
	mcrr	p15, 6, r2, r3, c2	@ Back to VMID #0
	isb				@ Not necessary if followed by eret

	pop	{r2, r3}
	bx	lr
ENDPROC(__kvm_tlb_flush_vmid)

/********************************************************************
 * Flush TLBs and instruction caches of all CPUs inside the inner-shareable
 * domain, for all VMIDs
 *
 * void __kvm_flush_vm_context(void);
 */
ENTRY(__kvm_flush_vm_context)
	mov	r0, #0			@ rn parameter for c15 flushes is SBZ

	/* Invalidate NS Non-Hyp TLB Inner Shareable (TLBIALLNSNHIS) */
	mcr     p15, 4, r0, c8, c3, 4
	/* Invalidate instruction caches Inner Shareable (ICIALLUIS) */
	mcr     p15, 0, r0, c7, c1, 0
	dsb
	isb				@ Not necessary if followed by eret

	bx	lr
ENDPROC(__kvm_flush_vm_context)


/********************************************************************
 *  Hypervisor world-switch code
 *
 *
 * int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 */
ENTRY(__kvm_vcpu_run)
	@ Save the vcpu pointer
	mcr	p15, 4, vcpu, c13, c0, 2	@ HTPIDR

	save_host_regs

	restore_vgic_state
	restore_timer_state

	@ Store hardware CP15 state and load guest state
	read_cp15_state store_to_vcpu = 0
	write_cp15_state read_from_vcpu = 1

	@ If the host kernel has not been configured with VFPv3 support,
	@ then it is safer if we deny guests from using it as well.
#ifdef CONFIG_VFPv3
	@ Set FPEXC_EN so the guest doesn't trap floating point instructions
	VFPFMRX r2, FPEXC		@ VMRS
	push	{r2}
	orr	r2, r2, #FPEXC_EN
	VFPFMXR FPEXC, r2		@ VMSR
#endif

	@ Configure Hyp-role
	configure_hyp_role vmentry

	@ Trap coprocessor CRx accesses
	set_hstr vmentry
	set_hcptr vmentry, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
	set_hdcr vmentry

	@ Write configured ID register into MIDR alias
	ldr	r1, [vcpu, #VCPU_MIDR]
	mcr	p15, 4, r1, c0, c0, 0

	@ Write guest view of MPIDR into VMPIDR
	ldr	r1, [vcpu, #CP15_OFFSET(c0_MPIDR)]
	mcr	p15, 4, r1, c0, c0, 5

	@ Set up guest memory translation
	ldr	r1, [vcpu, #VCPU_KVM]
	add	r1, r1, #KVM_VTTBR
	ldrd	r2, r3, [r1]
	mcrr	p15, 6, r2, r3, c2	@ Write VTTBR

	@ We're all done, just restore the GPRs and go to the guest
	restore_guest_regs
	clrex				@ Clear exclusive monitor
	eret

__kvm_vcpu_return:
	/*
	 * return convention:
	 * guest r0, r1, r2 saved on the stack
	 * r0: vcpu pointer
	 * r1: exception code
	 */
	save_guest_regs

	@ Set VMID == 0
	mov	r2, #0
	mov	r3, #0
	mcrr	p15, 6, r2, r3, c2	@ Write VTTBR

	@ Don't trap coprocessor accesses for host kernel
	set_hstr vmexit
	set_hdcr vmexit
	set_hcptr vmexit, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))

#ifdef CONFIG_VFPv3
	@ Save floating point registers we if let guest use them.
	tst	r2, #(HCPTR_TCP(10) | HCPTR_TCP(11))
	bne	after_vfp_restore

	@ Switch VFP/NEON hardware state to the host's
	add	r7, vcpu, #VCPU_VFP_GUEST
	store_vfp_state r7
	add	r7, vcpu, #VCPU_VFP_HOST
	ldr	r7, [r7]
	restore_vfp_state r7

after_vfp_restore:
	@ Restore FPEXC_EN which we clobbered on entry
	pop	{r2}
	VFPFMXR FPEXC, r2
#endif

	@ Reset Hyp-role
	configure_hyp_role vmexit

	@ Let host read hardware MIDR
	mrc	p15, 0, r2, c0, c0, 0
	mcr	p15, 4, r2, c0, c0, 0

	@ Back to hardware MPIDR
	mrc	p15, 0, r2, c0, c0, 5
	mcr	p15, 4, r2, c0, c0, 5

	@ Store guest CP15 state and restore host state
	read_cp15_state store_to_vcpu = 1
	write_cp15_state read_from_vcpu = 0

	save_timer_state
	save_vgic_state

	restore_host_regs
	clrex				@ Clear exclusive monitor
	mov	r0, r1			@ Return the return code
	mov	r1, #0			@ Clear upper bits in return value
	bx	lr			@ return to IOCTL

/********************************************************************
 *  Call function in Hyp mode
 *
 *
 * u64 kvm_call_hyp(void *hypfn, ...);
 *
 * This is not really a variadic function in the classic C-way and care must
 * be taken when calling this to ensure parameters are passed in registers
 * only, since the stack will change between the caller and the callee.
 *
 * Call the function with the first argument containing a pointer to the
 * function you wish to call in Hyp mode, and subsequent arguments will be
 * passed as r0, r1, and r2 (a maximum of 3 arguments in addition to the
 * function pointer can be passed).  The function being called must be mapped
 * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c).  Return values are
 * passed in r0 and r1.
 *
 * The calling convention follows the standard AAPCS:
 *   r0 - r3: caller save
 *   r12:     caller save
 *   rest:    callee save
 */
ENTRY(kvm_call_hyp)
	hvc	#0
	bx	lr

/********************************************************************
 * Hypervisor exception vector and handlers
 *
 *
 * The KVM/ARM Hypervisor ABI is defined as follows:
 *
 * Entry to Hyp mode from the host kernel will happen _only_ when an HVC
 * instruction is issued since all traps are disabled when running the host
 * kernel as per the Hyp-mode initialization at boot time.
 *
 * HVC instructions cause a trap to the vector page + offset 0x18 (see hyp_hvc
 * below) when the HVC instruction is called from SVC mode (i.e. a guest or the
 * host kernel) and they cause a trap to the vector page + offset 0xc when HVC
 * instructions are called from within Hyp-mode.
 *
 * Hyp-ABI: Calling HYP-mode functions from host (in SVC mode):
 *    Switching to Hyp mode is done through a simple HVC #0 instruction. The
 *    exception vector code will check that the HVC comes from VMID==0 and if
 *    so will push the necessary state (SPSR, lr_usr) on the Hyp stack.
 *    - r0 contains a pointer to a HYP function
 *    - r1, r2, and r3 contain arguments to the above function.
 *    - The HYP function will be called with its arguments in r0, r1 and r2.
 *    On HYP function return, we return directly to SVC.
 *
 * Note that the above is used to execute code in Hyp-mode from a host-kernel
 * point of view, and is a different concept from performing a world-switch and
 * executing guest code SVC mode (with a VMID != 0).
 */

/* Handle undef, svc, pabt, or dabt by crashing with a user notice */
.macro bad_exception exception_code, panic_str
	push	{r0-r2}
	mrrc	p15, 6, r0, r1, c2	@ Read VTTBR
	lsr	r1, r1, #16
	ands	r1, r1, #0xff
	beq	99f

	load_vcpu			@ Load VCPU pointer
	.if \exception_code == ARM_EXCEPTION_DATA_ABORT
	mrc	p15, 4, r2, c5, c2, 0	@ HSR
	mrc	p15, 4, r1, c6, c0, 0	@ HDFAR
	str	r2, [vcpu, #VCPU_HSR]
	str	r1, [vcpu, #VCPU_HxFAR]
	.endif
	.if \exception_code == ARM_EXCEPTION_PREF_ABORT
	mrc	p15, 4, r2, c5, c2, 0	@ HSR
	mrc	p15, 4, r1, c6, c0, 2	@ HIFAR
	str	r2, [vcpu, #VCPU_HSR]
	str	r1, [vcpu, #VCPU_HxFAR]
	.endif
	mov	r1, #\exception_code
	b	__kvm_vcpu_return

	@ We were in the host already. Let's craft a panic-ing return to SVC.
99:	mrs	r2, cpsr
	bic	r2, r2, #MODE_MASK
	orr	r2, r2, #SVC_MODE
THUMB(	orr	r2, r2, #PSR_T_BIT	)
	msr	spsr_cxsf, r2
	mrs	r1, ELR_hyp
	ldr	r2, =BSYM(panic)
	msr	ELR_hyp, r2
	ldr	r0, =\panic_str
	eret
.endm

	.text

	.align 5
__kvm_hyp_vector:
	.globl __kvm_hyp_vector

	@ Hyp-mode exception vector
	W(b)	hyp_reset
	W(b)	hyp_undef
	W(b)	hyp_svc
	W(b)	hyp_pabt
	W(b)	hyp_dabt
	W(b)	hyp_hvc
	W(b)	hyp_irq
	W(b)	hyp_fiq

	.align
hyp_reset:
	b	hyp_reset

	.align
hyp_undef:
	bad_exception ARM_EXCEPTION_UNDEFINED, und_die_str

	.align
hyp_svc:
	bad_exception ARM_EXCEPTION_HVC, svc_die_str

	.align
hyp_pabt:
	bad_exception ARM_EXCEPTION_PREF_ABORT, pabt_die_str

	.align
hyp_dabt:
	bad_exception ARM_EXCEPTION_DATA_ABORT, dabt_die_str

	.align
hyp_hvc:
	/*
	 * Getting here is either becuase of a trap from a guest or from calling
	 * HVC from the host kernel, which means "switch to Hyp mode".
	 */
	push	{r0, r1, r2}

	@ Check syndrome register
	mrc	p15, 4, r1, c5, c2, 0	@ HSR
	lsr	r0, r1, #HSR_EC_SHIFT
#ifdef CONFIG_VFPv3
	cmp	r0, #HSR_EC_CP_0_13
	beq	switch_to_guest_vfp
#endif
	cmp	r0, #HSR_EC_HVC
	bne	guest_trap		@ Not HVC instr.

	/*
	 * Let's check if the HVC came from VMID 0 and allow simple
	 * switch to Hyp mode
	 */
	mrrc    p15, 6, r0, r2, c2
	lsr     r2, r2, #16
	and     r2, r2, #0xff
	cmp     r2, #0
	bne	guest_trap		@ Guest called HVC

host_switch_to_hyp:
	pop	{r0, r1, r2}

	push	{lr}
	mrs	lr, SPSR
	push	{lr}

	mov	lr, r0
	mov	r0, r1
	mov	r1, r2
	mov	r2, r3

THUMB(	orr	lr, #1)
	blx	lr			@ Call the HYP function

	pop	{lr}
	msr	SPSR_csxf, lr
	pop	{lr}
	eret

guest_trap:
	load_vcpu			@ Load VCPU pointer to r0
	str	r1, [vcpu, #VCPU_HSR]

	@ Check if we need the fault information
	lsr	r1, r1, #HSR_EC_SHIFT
	cmp	r1, #HSR_EC_IABT
	mrceq	p15, 4, r2, c6, c0, 2	@ HIFAR
	beq	2f
	cmp	r1, #HSR_EC_DABT
	bne	1f
	mrc	p15, 4, r2, c6, c0, 0	@ HDFAR

2:	str	r2, [vcpu, #VCPU_HxFAR]

	/*
	 * B3.13.5 Reporting exceptions taken to the Non-secure PL2 mode:
	 *
	 * Abort on the stage 2 translation for a memory access from a
	 * Non-secure PL1 or PL0 mode:
	 *
	 * For any Access flag fault or Translation fault, and also for any
	 * Permission fault on the stage 2 translation of a memory access
	 * made as part of a translation table walk for a stage 1 translation,
	 * the HPFAR holds the IPA that caused the fault. Otherwise, the HPFAR
	 * is UNKNOWN.
	 */

	/* Check for permission fault, and S1PTW */
	mrc	p15, 4, r1, c5, c2, 0	@ HSR
	and	r0, r1, #HSR_FSC_TYPE
	cmp	r0, #FSC_PERM
	tsteq	r1, #(1 << 7)		@ S1PTW
	mrcne	p15, 4, r2, c6, c0, 4	@ HPFAR
	bne	3f

	/* Resolve IPA using the xFAR */
	mcr	p15, 0, r2, c7, c8, 0	@ ATS1CPR
	isb
	mrrc	p15, 0, r0, r1, c7	@ PAR
	tst	r0, #1
	bne	4f			@ Failed translation
	ubfx	r2, r0, #12, #20
	lsl	r2, r2, #4
	orr	r2, r2, r1, lsl #24

3:	load_vcpu			@ Load VCPU pointer to r0
	str	r2, [r0, #VCPU_HPFAR]

1:	mov	r1, #ARM_EXCEPTION_HVC
	b	__kvm_vcpu_return

4:	pop	{r0, r1, r2}		@ Failed translation, return to guest
	eret

/*
 * If VFPv3 support is not available, then we will not switch the VFP
 * registers; however cp10 and cp11 accesses will still trap and fallback
 * to the regular coprocessor emulation code, which currently will
 * inject an undefined exception to the guest.
 */
#ifdef CONFIG_VFPv3
switch_to_guest_vfp:
	load_vcpu			@ Load VCPU pointer to r0
	push	{r3-r7}

	@ NEON/VFP used.  Turn on VFP access.
	set_hcptr vmexit, (HCPTR_TCP(10) | HCPTR_TCP(11))

	@ Switch VFP/NEON hardware state to the guest's
	add	r7, r0, #VCPU_VFP_HOST
	ldr	r7, [r7]
	store_vfp_state r7
	add	r7, r0, #VCPU_VFP_GUEST
	restore_vfp_state r7

	pop	{r3-r7}
	pop	{r0-r2}
	eret
#endif

	.align
hyp_irq:
	push	{r0, r1, r2}
	mov	r1, #ARM_EXCEPTION_IRQ
	load_vcpu			@ Load VCPU pointer to r0
	b	__kvm_vcpu_return

	.align
hyp_fiq:
	b	hyp_fiq

	.ltorg

__kvm_hyp_code_end:
	.globl	__kvm_hyp_code_end

	.section ".rodata"

und_die_str:
	.ascii	"unexpected undefined exception in Hyp mode at: %#08x"
pabt_die_str:
	.ascii	"unexpected prefetch abort in Hyp mode at: %#08x"
dabt_die_str:
	.ascii	"unexpected data abort in Hyp mode at: %#08x"
svc_die_str:
	.ascii	"unexpected HVC/SVC trap in Hyp mode at: %#08x"