arch/powerpc/kvm/book3s_64_interrupts.S - linux - Git at Google

 /*
  * 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.
  *
  * Copyright SUSE Linux Products GmbH 2009
  *
  * Authors: Alexander Graf <agraf@suse.de>
  */

 #include <asm/ppc_asm.h>
 #include <asm/kvm_asm.h>
 #include <asm/reg.h>
 #include <asm/page.h>
 #include <asm/asm-offsets.h>
 #include <asm/exception-64s.h>

 #define KVMPPC_HANDLE_EXIT .kvmppc_handle_exit
 #define ULONG_SIZE 8
 #define VCPU_GPR(n)     (VCPU_GPRS + (n * ULONG_SIZE))

 .macro mfpaca tmp_reg, src_reg, offset, vcpu_reg
 	ld	\tmp_reg, (PACA_EXMC+\offset)(r13)
 	std	\tmp_reg, VCPU_GPR(\src_reg)(\vcpu_reg)
 .endm

 .macro DISABLE_INTERRUPTS
        mfmsr   r0
        rldicl  r0,r0,48,1
        rotldi  r0,r0,16
        mtmsrd  r0,1
 .endm

 /*****************************************************************************
  *                                                                           *
  *     Guest entry / exit code that is in kernel module memory (highmem)     *
  *                                                                           *
  ****************************************************************************/

 /* Registers:
  *  r3: kvm_run pointer
  *  r4: vcpu pointer
  */
 _GLOBAL(__kvmppc_vcpu_entry)

 kvm_start_entry:
 	/* Write correct stack frame */
 	mflr    r0
 	std     r0,16(r1)

 	/* Save host state to the stack */
 	stdu	r1, -SWITCH_FRAME_SIZE(r1)

 	/* Save r3 (kvm_run) and r4 (vcpu) */
 	SAVE_2GPRS(3, r1)

 	/* Save non-volatile registers (r14 - r31) */
 	SAVE_NVGPRS(r1)

 	/* Save LR */
 	mflr	r14
 	std	r14, _LINK(r1)

 /* XXX optimize non-volatile loading away */
 kvm_start_lightweight:

 	DISABLE_INTERRUPTS

 	/* Save R1/R2 in the PACA */
 	std	r1, PACAR1(r13)
 	std	r2, (PACA_EXMC+EX_SRR0)(r13)
 	ld	r3, VCPU_HIGHMEM_HANDLER(r4)
 	std	r3, PACASAVEDMSR(r13)

 	/* Load non-volatile guest state from the vcpu */
 	ld	r14, VCPU_GPR(r14)(r4)
 	ld	r15, VCPU_GPR(r15)(r4)
 	ld	r16, VCPU_GPR(r16)(r4)
 	ld	r17, VCPU_GPR(r17)(r4)
 	ld	r18, VCPU_GPR(r18)(r4)
 	ld	r19, VCPU_GPR(r19)(r4)
 	ld	r20, VCPU_GPR(r20)(r4)
 	ld	r21, VCPU_GPR(r21)(r4)
 	ld	r22, VCPU_GPR(r22)(r4)
 	ld	r23, VCPU_GPR(r23)(r4)
 	ld	r24, VCPU_GPR(r24)(r4)
 	ld	r25, VCPU_GPR(r25)(r4)
 	ld	r26, VCPU_GPR(r26)(r4)
 	ld	r27, VCPU_GPR(r27)(r4)
 	ld	r28, VCPU_GPR(r28)(r4)
 	ld	r29, VCPU_GPR(r29)(r4)
 	ld	r30, VCPU_GPR(r30)(r4)
 	ld	r31, VCPU_GPR(r31)(r4)

 	ld	r9, VCPU_PC(r4)			/* r9 = vcpu->arch.pc */
 	ld	r10, VCPU_SHADOW_MSR(r4)	/* r10 = vcpu->arch.shadow_msr */

 	ld	r3, VCPU_TRAMPOLINE_ENTER(r4)
 	mtsrr0	r3

 	LOAD_REG_IMMEDIATE(r3, MSR_KERNEL & ~(MSR_IR | MSR_DR))
 	mtsrr1	r3

 	/* Load guest state in the respective registers */
 	lwz	r3, VCPU_CR(r4)		/* r3 = vcpu->arch.cr */
 	stw	r3, (PACA_EXMC + EX_CCR)(r13)

 	ld	r3, VCPU_CTR(r4)	/* r3 = vcpu->arch.ctr */
 	mtctr	r3			/* CTR = r3 */

 	ld	r3, VCPU_LR(r4)		/* r3 = vcpu->arch.lr */
 	mtlr	r3			/* LR = r3 */

 	ld	r3, VCPU_XER(r4)	/* r3 = vcpu->arch.xer */
 	std	r3, (PACA_EXMC + EX_R3)(r13)

 	/* Some guests may need to have dcbz set to 32 byte length.
 	 *
 	 * Usually we ensure that by patching the guest's instructions
 	 * to trap on dcbz and emulate it in the hypervisor.
 	 *
 	 * If we can, we should tell the CPU to use 32 byte dcbz though,
 	 * because that's a lot faster.
 	 */

 	ld	r3, VCPU_HFLAGS(r4)
 	rldicl.	r3, r3, 0, 63		/* CR = ((r3 & 1) == 0) */
 	beq	no_dcbz32_on

 	mfspr   r3,SPRN_HID5
 	ori     r3, r3, 0x80		/* XXX HID5_dcbz32 = 0x80 */
 	mtspr   SPRN_HID5,r3

 no_dcbz32_on:
 	/*	Load guest GPRs */

 	ld	r3, VCPU_GPR(r9)(r4)
 	std	r3, (PACA_EXMC + EX_R9)(r13)
 	ld	r3, VCPU_GPR(r10)(r4)
 	std	r3, (PACA_EXMC + EX_R10)(r13)
 	ld	r3, VCPU_GPR(r11)(r4)
 	std	r3, (PACA_EXMC + EX_R11)(r13)
 	ld	r3, VCPU_GPR(r12)(r4)
 	std	r3, (PACA_EXMC + EX_R12)(r13)
 	ld	r3, VCPU_GPR(r13)(r4)
 	std	r3, (PACA_EXMC + EX_R13)(r13)

 	ld	r0, VCPU_GPR(r0)(r4)
 	ld	r1, VCPU_GPR(r1)(r4)
 	ld	r2, VCPU_GPR(r2)(r4)
 	ld	r3, VCPU_GPR(r3)(r4)
 	ld	r5, VCPU_GPR(r5)(r4)
 	ld	r6, VCPU_GPR(r6)(r4)
 	ld	r7, VCPU_GPR(r7)(r4)
 	ld	r8, VCPU_GPR(r8)(r4)
 	ld	r4, VCPU_GPR(r4)(r4)

 	/* This sets the Magic value for the trampoline */

 	li	r11, 1
 	stb	r11, PACA_KVM_IN_GUEST(r13)

 	/* Jump to SLB patching handlder and into our guest */
 	RFI

 /*
  * This is the handler in module memory. It gets jumped at from the
  * lowmem trampoline code, so it's basically the guest exit code.
  *
  */

 .global kvmppc_handler_highmem
 kvmppc_handler_highmem:

 	/*
 	 * Register usage at this point:
 	 *
 	 * R00   = guest R13
 	 * R01   = host R1
 	 * R02   = host R2
 	 * R10   = guest PC
 	 * R11   = guest MSR
 	 * R12   = exit handler id
 	 * R13   = PACA
 	 * PACA.exmc.R9    = guest R1
 	 * PACA.exmc.R10   = guest R10
 	 * PACA.exmc.R11   = guest R11
 	 * PACA.exmc.R12   = guest R12
 	 * PACA.exmc.R13   = guest R2
 	 * PACA.exmc.DAR   = guest DAR
 	 * PACA.exmc.DSISR = guest DSISR
 	 * PACA.exmc.LR    = guest instruction
 	 * PACA.exmc.CCR   = guest CR
 	 * PACA.exmc.SRR0  = guest R0
 	 *
 	 */

 	std	r3, (PACA_EXMC+EX_R3)(r13)

 	/* save the exit id in R3 */
 	mr	r3, r12

 	/* R12 = vcpu */
 	ld	r12, GPR4(r1)

 	/* Now save the guest state */

 	std	r0, VCPU_GPR(r13)(r12)
 	std	r4, VCPU_GPR(r4)(r12)
 	std	r5, VCPU_GPR(r5)(r12)
 	std	r6, VCPU_GPR(r6)(r12)
 	std	r7, VCPU_GPR(r7)(r12)
 	std	r8, VCPU_GPR(r8)(r12)
 	std	r9, VCPU_GPR(r9)(r12)

 	/* get registers from PACA */
 	mfpaca	r5, r0, EX_SRR0, r12
 	mfpaca	r5, r3, EX_R3, r12
 	mfpaca	r5, r1, EX_R9, r12
 	mfpaca	r5, r10, EX_R10, r12
 	mfpaca	r5, r11, EX_R11, r12
 	mfpaca	r5, r12, EX_R12, r12
 	mfpaca	r5, r2, EX_R13, r12

 	lwz	r5, (PACA_EXMC+EX_LR)(r13)
 	stw	r5, VCPU_LAST_INST(r12)

 	lwz	r5, (PACA_EXMC+EX_CCR)(r13)
 	stw	r5, VCPU_CR(r12)

 	ld	r5, VCPU_HFLAGS(r12)
 	rldicl.	r5, r5, 0, 63		/* CR = ((r5 & 1) == 0) */
 	beq	no_dcbz32_off

 	mfspr   r5,SPRN_HID5
 	rldimi  r5,r5,6,56
 	mtspr   SPRN_HID5,r5

 no_dcbz32_off:

 	/* XXX maybe skip on lightweight? */
 	std	r14, VCPU_GPR(r14)(r12)
 	std	r15, VCPU_GPR(r15)(r12)
 	std	r16, VCPU_GPR(r16)(r12)
 	std	r17, VCPU_GPR(r17)(r12)
 	std	r18, VCPU_GPR(r18)(r12)
 	std	r19, VCPU_GPR(r19)(r12)
 	std	r20, VCPU_GPR(r20)(r12)
 	std	r21, VCPU_GPR(r21)(r12)
 	std	r22, VCPU_GPR(r22)(r12)
 	std	r23, VCPU_GPR(r23)(r12)
 	std	r24, VCPU_GPR(r24)(r12)
 	std	r25, VCPU_GPR(r25)(r12)
 	std	r26, VCPU_GPR(r26)(r12)
 	std	r27, VCPU_GPR(r27)(r12)
 	std	r28, VCPU_GPR(r28)(r12)
 	std	r29, VCPU_GPR(r29)(r12)
 	std	r30, VCPU_GPR(r30)(r12)
 	std	r31, VCPU_GPR(r31)(r12)

 	/* Restore non-volatile host registers (r14 - r31) */
 	REST_NVGPRS(r1)

 	/* Save guest PC (R10) */
 	std	r10, VCPU_PC(r12)

 	/* Save guest msr (R11) */
 	std	r11, VCPU_SHADOW_MSR(r12)

 	/* Save guest CTR (in R12) */
 	mfctr	r5
 	std	r5, VCPU_CTR(r12)

 	/* Save guest LR */
 	mflr	r5
 	std	r5, VCPU_LR(r12)

 	/* Save guest XER */
 	mfxer	r5
 	std	r5, VCPU_XER(r12)

 	/* Save guest DAR */
 	ld	r5, (PACA_EXMC+EX_DAR)(r13)
 	std	r5, VCPU_FAULT_DEAR(r12)

 	/* Save guest DSISR */
 	lwz	r5, (PACA_EXMC+EX_DSISR)(r13)
 	std	r5, VCPU_FAULT_DSISR(r12)

 	/* Restore host msr -> SRR1 */
 	ld	r7, VCPU_HOST_MSR(r12)
 	mtsrr1	r7

 	/* Restore host IP -> SRR0 */
 	ld	r6, VCPU_HOST_RETIP(r12)
 	mtsrr0	r6

 	/*
 	 * For some interrupts, we need to call the real Linux
 	 * handler, so it can do work for us. This has to happen
 	 * as if the interrupt arrived from the kernel though,
 	 * so let's fake it here where most state is restored.
 	 *
 	 * Call Linux for hardware interrupts/decrementer
 	 * r3 = address of interrupt handler (exit reason)
 	 */

 	cmpwi	r3, BOOK3S_INTERRUPT_EXTERNAL
 	beq	call_linux_handler
 	cmpwi	r3, BOOK3S_INTERRUPT_DECREMENTER
 	beq	call_linux_handler

 	/* Back to Interruptable Mode! (goto kvm_return_point) */
 	RFI

 call_linux_handler:

 	/*
 	 * If we land here we need to jump back to the handler we
 	 * came from.
 	 *
 	 * We have a page that we can access from real mode, so let's
 	 * jump back to that and use it as a trampoline to get back into the
 	 * interrupt handler!
 	 *
 	 * R3 still contains the exit code,
 	 * R6 VCPU_HOST_RETIP and
 	 * R7 VCPU_HOST_MSR
 	 */

 	mtlr	r3

 	ld	r5, VCPU_TRAMPOLINE_LOWMEM(r12)
 	mtsrr0	r5
 	LOAD_REG_IMMEDIATE(r5, MSR_KERNEL & ~(MSR_IR | MSR_DR))
 	mtsrr1	r5

 	RFI

 .global kvm_return_point
 kvm_return_point:

 	/* Jump back to lightweight entry if we're supposed to */
 	/* go back into the guest */
 	mr	r5, r3
 	/* Restore r3 (kvm_run) and r4 (vcpu) */
 	REST_2GPRS(3, r1)
 	bl	KVMPPC_HANDLE_EXIT

 #if 0 /* XXX get lightweight exits back */
 	cmpwi	r3, RESUME_GUEST
 	bne	kvm_exit_heavyweight

 	/* put VCPU and KVM_RUN back into place and roll again! */
 	REST_2GPRS(3, r1)
 	b	kvm_start_lightweight

 kvm_exit_heavyweight:
 	/* Restore non-volatile host registers */
 	ld	r14, _LINK(r1)
 	mtlr	r14
 	REST_NVGPRS(r1)

 	addi    r1, r1, SWITCH_FRAME_SIZE
 #else
 	ld	r4, _LINK(r1)
 	mtlr	r4

 	cmpwi	r3, RESUME_GUEST
 	bne	kvm_exit_heavyweight

 	REST_2GPRS(3, r1)

 	addi    r1, r1, SWITCH_FRAME_SIZE

 	b	kvm_start_entry

 kvm_exit_heavyweight:

 	addi    r1, r1, SWITCH_FRAME_SIZE
 #endif

 	blr
	/*
	* 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.
	*
	* Copyright SUSE Linux Products GmbH 2009
	*
	* Authors: Alexander Graf <agraf@suse.de>
	*/

	#include <asm/ppc_asm.h>
	#include <asm/kvm_asm.h>
	#include <asm/reg.h>
	#include <asm/page.h>
	#include <asm/asm-offsets.h>
	#include <asm/exception-64s.h>

	#define KVMPPC_HANDLE_EXIT .kvmppc_handle_exit
	#define ULONG_SIZE 8
	#define VCPU_GPR(n) (VCPU_GPRS + (n * ULONG_SIZE))

	.macro mfpaca tmp_reg, src_reg, offset, vcpu_reg
	ld \tmp_reg, (PACA_EXMC+\offset)(r13)
	std \tmp_reg, VCPU_GPR(\src_reg)(\vcpu_reg)
	.endm

	.macro DISABLE_INTERRUPTS
	mfmsr r0
	rldicl r0,r0,48,1
	rotldi r0,r0,16
	mtmsrd r0,1
	.endm

	/*****************************************************************************
	* *
	* Guest entry / exit code that is in kernel module memory (highmem) *
	* *
	****************************************************************************/

	/* Registers:
	* r3: kvm_run pointer
	* r4: vcpu pointer
	*/
	_GLOBAL(__kvmppc_vcpu_entry)

	kvm_start_entry:
	/* Write correct stack frame */
	mflr r0
	std r0,16(r1)

	/* Save host state to the stack */
	stdu r1, -SWITCH_FRAME_SIZE(r1)

	/* Save r3 (kvm_run) and r4 (vcpu) */
	SAVE_2GPRS(3, r1)

	/* Save non-volatile registers (r14 - r31) */
	SAVE_NVGPRS(r1)

	/* Save LR */
	mflr r14
	std r14, _LINK(r1)

	/* XXX optimize non-volatile loading away */
	kvm_start_lightweight:

	DISABLE_INTERRUPTS

	/* Save R1/R2 in the PACA */
	std r1, PACAR1(r13)
	std r2, (PACA_EXMC+EX_SRR0)(r13)
	ld r3, VCPU_HIGHMEM_HANDLER(r4)
	std r3, PACASAVEDMSR(r13)

	/* Load non-volatile guest state from the vcpu */
	ld r14, VCPU_GPR(r14)(r4)
	ld r15, VCPU_GPR(r15)(r4)
	ld r16, VCPU_GPR(r16)(r4)
	ld r17, VCPU_GPR(r17)(r4)
	ld r18, VCPU_GPR(r18)(r4)
	ld r19, VCPU_GPR(r19)(r4)
	ld r20, VCPU_GPR(r20)(r4)
	ld r21, VCPU_GPR(r21)(r4)
	ld r22, VCPU_GPR(r22)(r4)
	ld r23, VCPU_GPR(r23)(r4)
	ld r24, VCPU_GPR(r24)(r4)
	ld r25, VCPU_GPR(r25)(r4)
	ld r26, VCPU_GPR(r26)(r4)
	ld r27, VCPU_GPR(r27)(r4)
	ld r28, VCPU_GPR(r28)(r4)
	ld r29, VCPU_GPR(r29)(r4)
	ld r30, VCPU_GPR(r30)(r4)
	ld r31, VCPU_GPR(r31)(r4)

	ld r9, VCPU_PC(r4) /* r9 = vcpu->arch.pc */
	ld r10, VCPU_SHADOW_MSR(r4) /* r10 = vcpu->arch.shadow_msr */

	ld r3, VCPU_TRAMPOLINE_ENTER(r4)
	mtsrr0 r3

	LOAD_REG_IMMEDIATE(r3, MSR_KERNEL & ~(MSR_IR \| MSR_DR))
	mtsrr1 r3

	/* Load guest state in the respective registers */
	lwz r3, VCPU_CR(r4) /* r3 = vcpu->arch.cr */
	stw r3, (PACA_EXMC + EX_CCR)(r13)

	ld r3, VCPU_CTR(r4) /* r3 = vcpu->arch.ctr */
	mtctr r3 /* CTR = r3 */

	ld r3, VCPU_LR(r4) /* r3 = vcpu->arch.lr */
	mtlr r3 /* LR = r3 */

	ld r3, VCPU_XER(r4) /* r3 = vcpu->arch.xer */
	std r3, (PACA_EXMC + EX_R3)(r13)

	/* Some guests may need to have dcbz set to 32 byte length.
	*
	* Usually we ensure that by patching the guest's instructions
	* to trap on dcbz and emulate it in the hypervisor.
	*
	* If we can, we should tell the CPU to use 32 byte dcbz though,
	* because that's a lot faster.
	*/

	ld r3, VCPU_HFLAGS(r4)
	rldicl. r3, r3, 0, 63 /* CR = ((r3 & 1) == 0) */
	beq no_dcbz32_on

	mfspr r3,SPRN_HID5
	ori r3, r3, 0x80 /* XXX HID5_dcbz32 = 0x80 */
	mtspr SPRN_HID5,r3

	no_dcbz32_on:
	/* Load guest GPRs */

	ld r3, VCPU_GPR(r9)(r4)
	std r3, (PACA_EXMC + EX_R9)(r13)
	ld r3, VCPU_GPR(r10)(r4)
	std r3, (PACA_EXMC + EX_R10)(r13)
	ld r3, VCPU_GPR(r11)(r4)
	std r3, (PACA_EXMC + EX_R11)(r13)
	ld r3, VCPU_GPR(r12)(r4)
	std r3, (PACA_EXMC + EX_R12)(r13)
	ld r3, VCPU_GPR(r13)(r4)
	std r3, (PACA_EXMC + EX_R13)(r13)

	ld r0, VCPU_GPR(r0)(r4)
	ld r1, VCPU_GPR(r1)(r4)
	ld r2, VCPU_GPR(r2)(r4)
	ld r3, VCPU_GPR(r3)(r4)
	ld r5, VCPU_GPR(r5)(r4)
	ld r6, VCPU_GPR(r6)(r4)
	ld r7, VCPU_GPR(r7)(r4)
	ld r8, VCPU_GPR(r8)(r4)
	ld r4, VCPU_GPR(r4)(r4)

	/* This sets the Magic value for the trampoline */

	li r11, 1
	stb r11, PACA_KVM_IN_GUEST(r13)

	/* Jump to SLB patching handlder and into our guest */
	RFI

	/*
	* This is the handler in module memory. It gets jumped at from the
	* lowmem trampoline code, so it's basically the guest exit code.
	*
	*/

	.global kvmppc_handler_highmem
	kvmppc_handler_highmem:

	/*
	* Register usage at this point:
	*
	* R00 = guest R13
	* R01 = host R1
	* R02 = host R2
	* R10 = guest PC
	* R11 = guest MSR
	* R12 = exit handler id
	* R13 = PACA
	* PACA.exmc.R9 = guest R1
	* PACA.exmc.R10 = guest R10
	* PACA.exmc.R11 = guest R11
	* PACA.exmc.R12 = guest R12
	* PACA.exmc.R13 = guest R2
	* PACA.exmc.DAR = guest DAR
	* PACA.exmc.DSISR = guest DSISR
	* PACA.exmc.LR = guest instruction
	* PACA.exmc.CCR = guest CR
	* PACA.exmc.SRR0 = guest R0
	*
	*/

	std r3, (PACA_EXMC+EX_R3)(r13)

	/* save the exit id in R3 */
	mr r3, r12

	/* R12 = vcpu */
	ld r12, GPR4(r1)

	/* Now save the guest state */

	std r0, VCPU_GPR(r13)(r12)
	std r4, VCPU_GPR(r4)(r12)
	std r5, VCPU_GPR(r5)(r12)
	std r6, VCPU_GPR(r6)(r12)
	std r7, VCPU_GPR(r7)(r12)
	std r8, VCPU_GPR(r8)(r12)
	std r9, VCPU_GPR(r9)(r12)

	/* get registers from PACA */
	mfpaca r5, r0, EX_SRR0, r12
	mfpaca r5, r3, EX_R3, r12
	mfpaca r5, r1, EX_R9, r12
	mfpaca r5, r10, EX_R10, r12
	mfpaca r5, r11, EX_R11, r12
	mfpaca r5, r12, EX_R12, r12
	mfpaca r5, r2, EX_R13, r12

	lwz r5, (PACA_EXMC+EX_LR)(r13)
	stw r5, VCPU_LAST_INST(r12)

	lwz r5, (PACA_EXMC+EX_CCR)(r13)
	stw r5, VCPU_CR(r12)

	ld r5, VCPU_HFLAGS(r12)
	rldicl. r5, r5, 0, 63 /* CR = ((r5 & 1) == 0) */
	beq no_dcbz32_off

	mfspr r5,SPRN_HID5
	rldimi r5,r5,6,56
	mtspr SPRN_HID5,r5

	no_dcbz32_off:

	/* XXX maybe skip on lightweight? */
	std r14, VCPU_GPR(r14)(r12)
	std r15, VCPU_GPR(r15)(r12)
	std r16, VCPU_GPR(r16)(r12)
	std r17, VCPU_GPR(r17)(r12)
	std r18, VCPU_GPR(r18)(r12)
	std r19, VCPU_GPR(r19)(r12)
	std r20, VCPU_GPR(r20)(r12)
	std r21, VCPU_GPR(r21)(r12)
	std r22, VCPU_GPR(r22)(r12)
	std r23, VCPU_GPR(r23)(r12)
	std r24, VCPU_GPR(r24)(r12)
	std r25, VCPU_GPR(r25)(r12)
	std r26, VCPU_GPR(r26)(r12)
	std r27, VCPU_GPR(r27)(r12)
	std r28, VCPU_GPR(r28)(r12)
	std r29, VCPU_GPR(r29)(r12)
	std r30, VCPU_GPR(r30)(r12)
	std r31, VCPU_GPR(r31)(r12)

	/* Restore non-volatile host registers (r14 - r31) */
	REST_NVGPRS(r1)

	/* Save guest PC (R10) */
	std r10, VCPU_PC(r12)

	/* Save guest msr (R11) */
	std r11, VCPU_SHADOW_MSR(r12)

	/* Save guest CTR (in R12) */
	mfctr r5
	std r5, VCPU_CTR(r12)

	/* Save guest LR */
	mflr r5
	std r5, VCPU_LR(r12)

	/* Save guest XER */
	mfxer r5
	std r5, VCPU_XER(r12)

	/* Save guest DAR */
	ld r5, (PACA_EXMC+EX_DAR)(r13)
	std r5, VCPU_FAULT_DEAR(r12)

	/* Save guest DSISR */
	lwz r5, (PACA_EXMC+EX_DSISR)(r13)
	std r5, VCPU_FAULT_DSISR(r12)

	/* Restore host msr -> SRR1 */
	ld r7, VCPU_HOST_MSR(r12)
	mtsrr1 r7

	/* Restore host IP -> SRR0 */
	ld r6, VCPU_HOST_RETIP(r12)
	mtsrr0 r6

	/*
	* For some interrupts, we need to call the real Linux
	* handler, so it can do work for us. This has to happen
	* as if the interrupt arrived from the kernel though,
	* so let's fake it here where most state is restored.
	*
	* Call Linux for hardware interrupts/decrementer
	* r3 = address of interrupt handler (exit reason)
	*/

	cmpwi r3, BOOK3S_INTERRUPT_EXTERNAL
	beq call_linux_handler
	cmpwi r3, BOOK3S_INTERRUPT_DECREMENTER
	beq call_linux_handler

	/* Back to Interruptable Mode! (goto kvm_return_point) */
	RFI

	call_linux_handler:

	/*
	* If we land here we need to jump back to the handler we
	* came from.
	*
	* We have a page that we can access from real mode, so let's
	* jump back to that and use it as a trampoline to get back into the
	* interrupt handler!
	*
	* R3 still contains the exit code,
	* R6 VCPU_HOST_RETIP and
	* R7 VCPU_HOST_MSR
	*/

	mtlr r3

	ld r5, VCPU_TRAMPOLINE_LOWMEM(r12)
	mtsrr0 r5
	LOAD_REG_IMMEDIATE(r5, MSR_KERNEL & ~(MSR_IR \| MSR_DR))
	mtsrr1 r5

	RFI

	.global kvm_return_point
	kvm_return_point:

	/* Jump back to lightweight entry if we're supposed to */
	/* go back into the guest */
	mr r5, r3
	/* Restore r3 (kvm_run) and r4 (vcpu) */
	REST_2GPRS(3, r1)
	bl KVMPPC_HANDLE_EXIT

	#if 0 /* XXX get lightweight exits back */
	cmpwi r3, RESUME_GUEST
	bne kvm_exit_heavyweight

	/* put VCPU and KVM_RUN back into place and roll again! */
	REST_2GPRS(3, r1)
	b kvm_start_lightweight

	kvm_exit_heavyweight:
	/* Restore non-volatile host registers */
	ld r14, _LINK(r1)
	mtlr r14
	REST_NVGPRS(r1)

	addi r1, r1, SWITCH_FRAME_SIZE
	#else
	ld r4, _LINK(r1)
	mtlr r4

	cmpwi r3, RESUME_GUEST
	bne kvm_exit_heavyweight

	REST_2GPRS(3, r1)

	addi r1, r1, SWITCH_FRAME_SIZE

	b kvm_start_entry

	kvm_exit_heavyweight:

	addi r1, r1, SWITCH_FRAME_SIZE
	#endif

	blr