arch/powerpc/kvm/emulate.c - maze/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 IBM Corp. 2007
  * Copyright 2011 Freescale Semiconductor, Inc.
  *
  * Authors: Hollis Blanchard <hollisb@us.ibm.com>
  */

 #include <linux/jiffies.h>
 #include <linux/hrtimer.h>
 #include <linux/types.h>
 #include <linux/string.h>
 #include <linux/kvm_host.h>
 #include <linux/clockchips.h>

 #include <asm/reg.h>
 #include <asm/time.h>
 #include <asm/byteorder.h>
 #include <asm/kvm_ppc.h>
 #include <asm/disassemble.h>
 #include "timing.h"
 #include "trace.h"

 #define OP_TRAP 3
 #define OP_TRAP_64 2

 #define OP_31_XOP_TRAP      4
 #define OP_31_XOP_LWZX      23
 #define OP_31_XOP_TRAP_64   68
 #define OP_31_XOP_DCBF      86
 #define OP_31_XOP_LBZX      87
 #define OP_31_XOP_STWX      151
 #define OP_31_XOP_STBX      215
 #define OP_31_XOP_LBZUX     119
 #define OP_31_XOP_STBUX     247
 #define OP_31_XOP_LHZX      279
 #define OP_31_XOP_LHZUX     311
 #define OP_31_XOP_MFSPR     339
 #define OP_31_XOP_LHAX      343
 #define OP_31_XOP_STHX      407
 #define OP_31_XOP_STHUX     439
 #define OP_31_XOP_MTSPR     467
 #define OP_31_XOP_DCBI      470
 #define OP_31_XOP_LWBRX     534
 #define OP_31_XOP_TLBSYNC   566
 #define OP_31_XOP_STWBRX    662
 #define OP_31_XOP_LHBRX     790
 #define OP_31_XOP_STHBRX    918

 #define OP_LWZ  32
 #define OP_LD   58
 #define OP_LWZU 33
 #define OP_LBZ  34
 #define OP_LBZU 35
 #define OP_STW  36
 #define OP_STWU 37
 #define OP_STD  62
 #define OP_STB  38
 #define OP_STBU 39
 #define OP_LHZ  40
 #define OP_LHZU 41
 #define OP_LHA  42
 #define OP_LHAU 43
 #define OP_STH  44
 #define OP_STHU 45

 void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
 {
 	unsigned long dec_nsec;
 	unsigned long long dec_time;

 	pr_debug("mtDEC: %x\n", vcpu->arch.dec);
 	hrtimer_try_to_cancel(&vcpu->arch.dec_timer);

 #ifdef CONFIG_PPC_BOOK3S
 	/* mtdec lowers the interrupt line when positive. */
 	kvmppc_core_dequeue_dec(vcpu);

 	/* POWER4+ triggers a dec interrupt if the value is < 0 */
 	if (vcpu->arch.dec & 0x80000000) {
 		kvmppc_core_queue_dec(vcpu);
 		return;
 	}
 #endif

 #ifdef CONFIG_BOOKE
 	/* On BOOKE, DEC = 0 is as good as decrementer not enabled */
 	if (vcpu->arch.dec == 0)
 		return;
 #endif

 	/*
 	 * The decrementer ticks at the same rate as the timebase, so
 	 * that's how we convert the guest DEC value to the number of
 	 * host ticks.
 	 */

 	dec_time = vcpu->arch.dec;
 	/*
 	 * Guest timebase ticks at the same frequency as host decrementer.
 	 * So use the host decrementer calculations for decrementer emulation.
 	 */
 	dec_time = dec_time << decrementer_clockevent.shift;
 	do_div(dec_time, decrementer_clockevent.mult);
 	dec_nsec = do_div(dec_time, NSEC_PER_SEC);
 	hrtimer_start(&vcpu->arch.dec_timer,
 		ktime_set(dec_time, dec_nsec), HRTIMER_MODE_REL);
 	vcpu->arch.dec_jiffies = get_tb();
 }

 u32 kvmppc_get_dec(struct kvm_vcpu *vcpu, u64 tb)
 {
 	u64 jd = tb - vcpu->arch.dec_jiffies;

 #ifdef CONFIG_BOOKE
 	if (vcpu->arch.dec < jd)
 		return 0;
 #endif

 	return vcpu->arch.dec - jd;
 }

 static int kvmppc_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
 {
 	enum emulation_result emulated = EMULATE_DONE;
 	ulong spr_val = kvmppc_get_gpr(vcpu, rs);

 	switch (sprn) {
 	case SPRN_SRR0:
 		vcpu->arch.shared->srr0 = spr_val;
 		break;
 	case SPRN_SRR1:
 		vcpu->arch.shared->srr1 = spr_val;
 		break;

 	/* XXX We need to context-switch the timebase for
 	 * watchdog and FIT. */
 	case SPRN_TBWL: break;
 	case SPRN_TBWU: break;

 	case SPRN_DEC:
 		vcpu->arch.dec = spr_val;
 		kvmppc_emulate_dec(vcpu);
 		break;

 	case SPRN_SPRG0:
 		vcpu->arch.shared->sprg0 = spr_val;
 		break;
 	case SPRN_SPRG1:
 		vcpu->arch.shared->sprg1 = spr_val;
 		break;
 	case SPRN_SPRG2:
 		vcpu->arch.shared->sprg2 = spr_val;
 		break;
 	case SPRN_SPRG3:
 		vcpu->arch.shared->sprg3 = spr_val;
 		break;

 	default:
 		emulated = kvmppc_core_emulate_mtspr(vcpu, sprn,
 						     spr_val);
 		if (emulated == EMULATE_FAIL)
 			printk(KERN_INFO "mtspr: unknown spr "
 				"0x%x\n", sprn);
 		break;
 	}

 	kvmppc_set_exit_type(vcpu, EMULATED_MTSPR_EXITS);

 	return emulated;
 }

 static int kvmppc_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
 {
 	enum emulation_result emulated = EMULATE_DONE;
 	ulong spr_val = 0;

 	switch (sprn) {
 	case SPRN_SRR0:
 		spr_val = vcpu->arch.shared->srr0;
 		break;
 	case SPRN_SRR1:
 		spr_val = vcpu->arch.shared->srr1;
 		break;
 	case SPRN_PVR:
 		spr_val = vcpu->arch.pvr;
 		break;
 	case SPRN_PIR:
 		spr_val = vcpu->vcpu_id;
 		break;

 	/* Note: mftb and TBRL/TBWL are user-accessible, so
 	 * the guest can always access the real TB anyways.
 	 * In fact, we probably will never see these traps. */
 	case SPRN_TBWL:
 		spr_val = get_tb() >> 32;
 		break;
 	case SPRN_TBWU:
 		spr_val = get_tb();
 		break;

 	case SPRN_SPRG0:
 		spr_val = vcpu->arch.shared->sprg0;
 		break;
 	case SPRN_SPRG1:
 		spr_val = vcpu->arch.shared->sprg1;
 		break;
 	case SPRN_SPRG2:
 		spr_val = vcpu->arch.shared->sprg2;
 		break;
 	case SPRN_SPRG3:
 		spr_val = vcpu->arch.shared->sprg3;
 		break;
 	/* Note: SPRG4-7 are user-readable, so we don't get
 	 * a trap. */

 	case SPRN_DEC:
 		spr_val = kvmppc_get_dec(vcpu, get_tb());
 		break;
 	default:
 		emulated = kvmppc_core_emulate_mfspr(vcpu, sprn,
 						     &spr_val);
 		if (unlikely(emulated == EMULATE_FAIL)) {
 			printk(KERN_INFO "mfspr: unknown spr "
 				"0x%x\n", sprn);
 		}
 		break;
 	}

 	if (emulated == EMULATE_DONE)
 		kvmppc_set_gpr(vcpu, rt, spr_val);
 	kvmppc_set_exit_type(vcpu, EMULATED_MFSPR_EXITS);

 	return emulated;
 }

 /* XXX to do:
  * lhax
  * lhaux
  * lswx
  * lswi
  * stswx
  * stswi
  * lha
  * lhau
  * lmw
  * stmw
  *
  * XXX is_bigendian should depend on MMU mapping or MSR[LE]
  */
 /* XXX Should probably auto-generate instruction decoding for a particular core
  * from opcode tables in the future. */
 int kvmppc_emulate_instruction(struct kvm_run *run, struct kvm_vcpu *vcpu)
 {
 	u32 inst = kvmppc_get_last_inst(vcpu);
 	int ra = get_ra(inst);
 	int rs = get_rs(inst);
 	int rt = get_rt(inst);
 	int sprn = get_sprn(inst);
 	enum emulation_result emulated = EMULATE_DONE;
 	int advance = 1;

 	/* this default type might be overwritten by subcategories */
 	kvmppc_set_exit_type(vcpu, EMULATED_INST_EXITS);

 	pr_debug("Emulating opcode %d / %d\n", get_op(inst), get_xop(inst));

 	switch (get_op(inst)) {
 	case OP_TRAP:
 #ifdef CONFIG_PPC_BOOK3S
 	case OP_TRAP_64:
 		kvmppc_core_queue_program(vcpu, SRR1_PROGTRAP);
 #else
 		kvmppc_core_queue_program(vcpu,
 					  vcpu->arch.shared->esr | ESR_PTR);
 #endif
 		advance = 0;
 		break;

 	case 31:
 		switch (get_xop(inst)) {

 		case OP_31_XOP_TRAP:
 #ifdef CONFIG_64BIT
 		case OP_31_XOP_TRAP_64:
 #endif
 #ifdef CONFIG_PPC_BOOK3S
 			kvmppc_core_queue_program(vcpu, SRR1_PROGTRAP);
 #else
 			kvmppc_core_queue_program(vcpu,
 					vcpu->arch.shared->esr | ESR_PTR);
 #endif
 			advance = 0;
 			break;
 		case OP_31_XOP_LWZX:
 			emulated = kvmppc_handle_load(run, vcpu, rt, 4, 1);
 			break;

 		case OP_31_XOP_LBZX:
 			emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
 			break;

 		case OP_31_XOP_LBZUX:
 			emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
 			kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 			break;

 		case OP_31_XOP_STWX:
 			emulated = kvmppc_handle_store(run, vcpu,
 						       kvmppc_get_gpr(vcpu, rs),
 			                               4, 1);
 			break;

 		case OP_31_XOP_STBX:
 			emulated = kvmppc_handle_store(run, vcpu,
 						       kvmppc_get_gpr(vcpu, rs),
 			                               1, 1);
 			break;

 		case OP_31_XOP_STBUX:
 			emulated = kvmppc_handle_store(run, vcpu,
 						       kvmppc_get_gpr(vcpu, rs),
 			                               1, 1);
 			kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 			break;

 		case OP_31_XOP_LHAX:
 			emulated = kvmppc_handle_loads(run, vcpu, rt, 2, 1);
 			break;

 		case OP_31_XOP_LHZX:
 			emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
 			break;

 		case OP_31_XOP_LHZUX:
 			emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
 			kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 			break;

 		case OP_31_XOP_MFSPR:
 			emulated = kvmppc_emulate_mfspr(vcpu, sprn, rt);
 			break;

 		case OP_31_XOP_STHX:
 			emulated = kvmppc_handle_store(run, vcpu,
 						       kvmppc_get_gpr(vcpu, rs),
 			                               2, 1);
 			break;

 		case OP_31_XOP_STHUX:
 			emulated = kvmppc_handle_store(run, vcpu,
 						       kvmppc_get_gpr(vcpu, rs),
 			                               2, 1);
 			kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 			break;

 		case OP_31_XOP_MTSPR:
 			emulated = kvmppc_emulate_mtspr(vcpu, sprn, rs);
 			break;

 		case OP_31_XOP_DCBF:
 		case OP_31_XOP_DCBI:
 			/* Do nothing. The guest is performing dcbi because
 			 * hardware DMA is not snooped by the dcache, but
 			 * emulated DMA either goes through the dcache as
 			 * normal writes, or the host kernel has handled dcache
 			 * coherence. */
 			break;

 		case OP_31_XOP_LWBRX:
 			emulated = kvmppc_handle_load(run, vcpu, rt, 4, 0);
 			break;

 		case OP_31_XOP_TLBSYNC:
 			break;

 		case OP_31_XOP_STWBRX:
 			emulated = kvmppc_handle_store(run, vcpu,
 						       kvmppc_get_gpr(vcpu, rs),
 			                               4, 0);
 			break;

 		case OP_31_XOP_LHBRX:
 			emulated = kvmppc_handle_load(run, vcpu, rt, 2, 0);
 			break;

 		case OP_31_XOP_STHBRX:
 			emulated = kvmppc_handle_store(run, vcpu,
 						       kvmppc_get_gpr(vcpu, rs),
 			                               2, 0);
 			break;

 		default:
 			/* Attempt core-specific emulation below. */
 			emulated = EMULATE_FAIL;
 		}
 		break;

 	case OP_LWZ:
 		emulated = kvmppc_handle_load(run, vcpu, rt, 4, 1);
 		break;

 	/* TBD: Add support for other 64 bit load variants like ldu, ldux, ldx etc. */
 	case OP_LD:
 		rt = get_rt(inst);
 		emulated = kvmppc_handle_load(run, vcpu, rt, 8, 1);
 		break;

 	case OP_LWZU:
 		emulated = kvmppc_handle_load(run, vcpu, rt, 4, 1);
 		kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 		break;

 	case OP_LBZ:
 		emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
 		break;

 	case OP_LBZU:
 		emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
 		kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 		break;

 	case OP_STW:
 		emulated = kvmppc_handle_store(run, vcpu,
 					       kvmppc_get_gpr(vcpu, rs),
 		                               4, 1);
 		break;

 	/* TBD: Add support for other 64 bit store variants like stdu, stdux, stdx etc. */
 	case OP_STD:
 		rs = get_rs(inst);
 		emulated = kvmppc_handle_store(run, vcpu,
 					       kvmppc_get_gpr(vcpu, rs),
 		                               8, 1);
 		break;

 	case OP_STWU:
 		emulated = kvmppc_handle_store(run, vcpu,
 					       kvmppc_get_gpr(vcpu, rs),
 		                               4, 1);
 		kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 		break;

 	case OP_STB:
 		emulated = kvmppc_handle_store(run, vcpu,
 					       kvmppc_get_gpr(vcpu, rs),
 		                               1, 1);
 		break;

 	case OP_STBU:
 		emulated = kvmppc_handle_store(run, vcpu,
 					       kvmppc_get_gpr(vcpu, rs),
 		                               1, 1);
 		kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 		break;

 	case OP_LHZ:
 		emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
 		break;

 	case OP_LHZU:
 		emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
 		kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 		break;

 	case OP_LHA:
 		emulated = kvmppc_handle_loads(run, vcpu, rt, 2, 1);
 		break;

 	case OP_LHAU:
 		emulated = kvmppc_handle_loads(run, vcpu, rt, 2, 1);
 		kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 		break;

 	case OP_STH:
 		emulated = kvmppc_handle_store(run, vcpu,
 					       kvmppc_get_gpr(vcpu, rs),
 		                               2, 1);
 		break;

 	case OP_STHU:
 		emulated = kvmppc_handle_store(run, vcpu,
 					       kvmppc_get_gpr(vcpu, rs),
 		                               2, 1);
 		kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
 		break;

 	default:
 		emulated = EMULATE_FAIL;
 	}

 	if (emulated == EMULATE_FAIL) {
 		emulated = kvmppc_core_emulate_op(run, vcpu, inst, &advance);
 		if (emulated == EMULATE_AGAIN) {
 			advance = 0;
 		} else if (emulated == EMULATE_FAIL) {
 			advance = 0;
 			printk(KERN_ERR "Couldn't emulate instruction 0x%08x "
 			       "(op %d xop %d)\n", inst, get_op(inst), get_xop(inst));
 			kvmppc_core_queue_program(vcpu, 0);
 		}
 	}

 	trace_kvm_ppc_instr(inst, kvmppc_get_pc(vcpu), emulated);

 	/* Advance past emulated instruction. */
 	if (advance)
 		kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);

 	return emulated;
 }
	/*
	* 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 IBM Corp. 2007
	* Copyright 2011 Freescale Semiconductor, Inc.
	*
	* Authors: Hollis Blanchard <hollisb@us.ibm.com>
	*/

	#include <linux/jiffies.h>
	#include <linux/hrtimer.h>
	#include <linux/types.h>
	#include <linux/string.h>
	#include <linux/kvm_host.h>
	#include <linux/clockchips.h>

	#include <asm/reg.h>
	#include <asm/time.h>
	#include <asm/byteorder.h>
	#include <asm/kvm_ppc.h>
	#include <asm/disassemble.h>
	#include "timing.h"
	#include "trace.h"

	#define OP_TRAP 3
	#define OP_TRAP_64 2

	#define OP_31_XOP_TRAP 4
	#define OP_31_XOP_LWZX 23
	#define OP_31_XOP_TRAP_64 68
	#define OP_31_XOP_DCBF 86
	#define OP_31_XOP_LBZX 87
	#define OP_31_XOP_STWX 151
	#define OP_31_XOP_STBX 215
	#define OP_31_XOP_LBZUX 119
	#define OP_31_XOP_STBUX 247
	#define OP_31_XOP_LHZX 279
	#define OP_31_XOP_LHZUX 311
	#define OP_31_XOP_MFSPR 339
	#define OP_31_XOP_LHAX 343
	#define OP_31_XOP_STHX 407
	#define OP_31_XOP_STHUX 439
	#define OP_31_XOP_MTSPR 467
	#define OP_31_XOP_DCBI 470
	#define OP_31_XOP_LWBRX 534
	#define OP_31_XOP_TLBSYNC 566
	#define OP_31_XOP_STWBRX 662
	#define OP_31_XOP_LHBRX 790
	#define OP_31_XOP_STHBRX 918

	#define OP_LWZ 32
	#define OP_LD 58
	#define OP_LWZU 33
	#define OP_LBZ 34
	#define OP_LBZU 35
	#define OP_STW 36
	#define OP_STWU 37
	#define OP_STD 62
	#define OP_STB 38
	#define OP_STBU 39
	#define OP_LHZ 40
	#define OP_LHZU 41
	#define OP_LHA 42
	#define OP_LHAU 43
	#define OP_STH 44
	#define OP_STHU 45

	void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
	{
	unsigned long dec_nsec;
	unsigned long long dec_time;

	pr_debug("mtDEC: %x\n", vcpu->arch.dec);
	hrtimer_try_to_cancel(&vcpu->arch.dec_timer);

	#ifdef CONFIG_PPC_BOOK3S
	/* mtdec lowers the interrupt line when positive. */
	kvmppc_core_dequeue_dec(vcpu);

	/* POWER4+ triggers a dec interrupt if the value is < 0 */
	if (vcpu->arch.dec & 0x80000000) {
	kvmppc_core_queue_dec(vcpu);
	return;
	}
	#endif

	#ifdef CONFIG_BOOKE
	/* On BOOKE, DEC = 0 is as good as decrementer not enabled */
	if (vcpu->arch.dec == 0)
	return;
	#endif

	/*
	* The decrementer ticks at the same rate as the timebase, so
	* that's how we convert the guest DEC value to the number of
	* host ticks.
	*/

	dec_time = vcpu->arch.dec;
	/*
	* Guest timebase ticks at the same frequency as host decrementer.
	* So use the host decrementer calculations for decrementer emulation.
	*/
	dec_time = dec_time << decrementer_clockevent.shift;
	do_div(dec_time, decrementer_clockevent.mult);
	dec_nsec = do_div(dec_time, NSEC_PER_SEC);
	hrtimer_start(&vcpu->arch.dec_timer,
	ktime_set(dec_time, dec_nsec), HRTIMER_MODE_REL);
	vcpu->arch.dec_jiffies = get_tb();
	}

	u32 kvmppc_get_dec(struct kvm_vcpu *vcpu, u64 tb)
	{
	u64 jd = tb - vcpu->arch.dec_jiffies;

	#ifdef CONFIG_BOOKE
	if (vcpu->arch.dec < jd)
	return 0;
	#endif

	return vcpu->arch.dec - jd;
	}

	static int kvmppc_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
	{
	enum emulation_result emulated = EMULATE_DONE;
	ulong spr_val = kvmppc_get_gpr(vcpu, rs);

	switch (sprn) {
	case SPRN_SRR0:
	vcpu->arch.shared->srr0 = spr_val;
	break;
	case SPRN_SRR1:
	vcpu->arch.shared->srr1 = spr_val;
	break;

	/* XXX We need to context-switch the timebase for
	* watchdog and FIT. */
	case SPRN_TBWL: break;
	case SPRN_TBWU: break;

	case SPRN_DEC:
	vcpu->arch.dec = spr_val;
	kvmppc_emulate_dec(vcpu);
	break;

	case SPRN_SPRG0:
	vcpu->arch.shared->sprg0 = spr_val;
	break;
	case SPRN_SPRG1:
	vcpu->arch.shared->sprg1 = spr_val;
	break;
	case SPRN_SPRG2:
	vcpu->arch.shared->sprg2 = spr_val;
	break;
	case SPRN_SPRG3:
	vcpu->arch.shared->sprg3 = spr_val;
	break;

	default:
	emulated = kvmppc_core_emulate_mtspr(vcpu, sprn,
	spr_val);
	if (emulated == EMULATE_FAIL)
	printk(KERN_INFO "mtspr: unknown spr "
	"0x%x\n", sprn);
	break;
	}

	kvmppc_set_exit_type(vcpu, EMULATED_MTSPR_EXITS);

	return emulated;
	}

	static int kvmppc_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
	{
	enum emulation_result emulated = EMULATE_DONE;
	ulong spr_val = 0;

	switch (sprn) {
	case SPRN_SRR0:
	spr_val = vcpu->arch.shared->srr0;
	break;
	case SPRN_SRR1:
	spr_val = vcpu->arch.shared->srr1;
	break;
	case SPRN_PVR:
	spr_val = vcpu->arch.pvr;
	break;
	case SPRN_PIR:
	spr_val = vcpu->vcpu_id;
	break;

	/* Note: mftb and TBRL/TBWL are user-accessible, so
	* the guest can always access the real TB anyways.
	* In fact, we probably will never see these traps. */
	case SPRN_TBWL:
	spr_val = get_tb() >> 32;
	break;
	case SPRN_TBWU:
	spr_val = get_tb();
	break;

	case SPRN_SPRG0:
	spr_val = vcpu->arch.shared->sprg0;
	break;
	case SPRN_SPRG1:
	spr_val = vcpu->arch.shared->sprg1;
	break;
	case SPRN_SPRG2:
	spr_val = vcpu->arch.shared->sprg2;
	break;
	case SPRN_SPRG3:
	spr_val = vcpu->arch.shared->sprg3;
	break;
	/* Note: SPRG4-7 are user-readable, so we don't get
	* a trap. */

	case SPRN_DEC:
	spr_val = kvmppc_get_dec(vcpu, get_tb());
	break;
	default:
	emulated = kvmppc_core_emulate_mfspr(vcpu, sprn,
	&spr_val);
	if (unlikely(emulated == EMULATE_FAIL)) {
	printk(KERN_INFO "mfspr: unknown spr "
	"0x%x\n", sprn);
	}
	break;
	}

	if (emulated == EMULATE_DONE)
	kvmppc_set_gpr(vcpu, rt, spr_val);
	kvmppc_set_exit_type(vcpu, EMULATED_MFSPR_EXITS);

	return emulated;
	}

	/* XXX to do:
	* lhax
	* lhaux
	* lswx
	* lswi
	* stswx
	* stswi
	* lha
	* lhau
	* lmw
	* stmw
	*
	* XXX is_bigendian should depend on MMU mapping or MSR[LE]
	*/
	/* XXX Should probably auto-generate instruction decoding for a particular core
	* from opcode tables in the future. */
	int kvmppc_emulate_instruction(struct kvm_run run, struct kvm_vcpu vcpu)
	{
	u32 inst = kvmppc_get_last_inst(vcpu);
	int ra = get_ra(inst);
	int rs = get_rs(inst);
	int rt = get_rt(inst);
	int sprn = get_sprn(inst);
	enum emulation_result emulated = EMULATE_DONE;
	int advance = 1;

	/* this default type might be overwritten by subcategories */
	kvmppc_set_exit_type(vcpu, EMULATED_INST_EXITS);

	pr_debug("Emulating opcode %d / %d\n", get_op(inst), get_xop(inst));

	switch (get_op(inst)) {
	case OP_TRAP:
	#ifdef CONFIG_PPC_BOOK3S
	case OP_TRAP_64:
	kvmppc_core_queue_program(vcpu, SRR1_PROGTRAP);
	#else
	kvmppc_core_queue_program(vcpu,
	vcpu->arch.shared->esr \| ESR_PTR);
	#endif
	advance = 0;
	break;

	case 31:
	switch (get_xop(inst)) {

	case OP_31_XOP_TRAP:
	#ifdef CONFIG_64BIT
	case OP_31_XOP_TRAP_64:
	#endif
	#ifdef CONFIG_PPC_BOOK3S
	kvmppc_core_queue_program(vcpu, SRR1_PROGTRAP);
	#else
	kvmppc_core_queue_program(vcpu,
	vcpu->arch.shared->esr \| ESR_PTR);
	#endif
	advance = 0;
	break;
	case OP_31_XOP_LWZX:
	emulated = kvmppc_handle_load(run, vcpu, rt, 4, 1);
	break;

	case OP_31_XOP_LBZX:
	emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
	break;

	case OP_31_XOP_LBZUX:
	emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_31_XOP_STWX:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	4, 1);
	break;

	case OP_31_XOP_STBX:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	1, 1);
	break;

	case OP_31_XOP_STBUX:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	1, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_31_XOP_LHAX:
	emulated = kvmppc_handle_loads(run, vcpu, rt, 2, 1);
	break;

	case OP_31_XOP_LHZX:
	emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
	break;

	case OP_31_XOP_LHZUX:
	emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_31_XOP_MFSPR:
	emulated = kvmppc_emulate_mfspr(vcpu, sprn, rt);
	break;

	case OP_31_XOP_STHX:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	2, 1);
	break;

	case OP_31_XOP_STHUX:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	2, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_31_XOP_MTSPR:
	emulated = kvmppc_emulate_mtspr(vcpu, sprn, rs);
	break;

	case OP_31_XOP_DCBF:
	case OP_31_XOP_DCBI:
	/* Do nothing. The guest is performing dcbi because
	* hardware DMA is not snooped by the dcache, but
	* emulated DMA either goes through the dcache as
	* normal writes, or the host kernel has handled dcache
	* coherence. */
	break;

	case OP_31_XOP_LWBRX:
	emulated = kvmppc_handle_load(run, vcpu, rt, 4, 0);
	break;

	case OP_31_XOP_TLBSYNC:
	break;

	case OP_31_XOP_STWBRX:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	4, 0);
	break;

	case OP_31_XOP_LHBRX:
	emulated = kvmppc_handle_load(run, vcpu, rt, 2, 0);
	break;

	case OP_31_XOP_STHBRX:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	2, 0);
	break;

	default:
	/* Attempt core-specific emulation below. */
	emulated = EMULATE_FAIL;
	}
	break;

	case OP_LWZ:
	emulated = kvmppc_handle_load(run, vcpu, rt, 4, 1);
	break;

	/* TBD: Add support for other 64 bit load variants like ldu, ldux, ldx etc. */
	case OP_LD:
	rt = get_rt(inst);
	emulated = kvmppc_handle_load(run, vcpu, rt, 8, 1);
	break;

	case OP_LWZU:
	emulated = kvmppc_handle_load(run, vcpu, rt, 4, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_LBZ:
	emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
	break;

	case OP_LBZU:
	emulated = kvmppc_handle_load(run, vcpu, rt, 1, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_STW:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	4, 1);
	break;

	/* TBD: Add support for other 64 bit store variants like stdu, stdux, stdx etc. */
	case OP_STD:
	rs = get_rs(inst);
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	8, 1);
	break;

	case OP_STWU:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	4, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_STB:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	1, 1);
	break;

	case OP_STBU:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	1, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_LHZ:
	emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
	break;

	case OP_LHZU:
	emulated = kvmppc_handle_load(run, vcpu, rt, 2, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_LHA:
	emulated = kvmppc_handle_loads(run, vcpu, rt, 2, 1);
	break;

	case OP_LHAU:
	emulated = kvmppc_handle_loads(run, vcpu, rt, 2, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	case OP_STH:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	2, 1);
	break;

	case OP_STHU:
	emulated = kvmppc_handle_store(run, vcpu,
	kvmppc_get_gpr(vcpu, rs),
	2, 1);
	kvmppc_set_gpr(vcpu, ra, vcpu->arch.vaddr_accessed);
	break;

	default:
	emulated = EMULATE_FAIL;
	}

	if (emulated == EMULATE_FAIL) {
	emulated = kvmppc_core_emulate_op(run, vcpu, inst, &advance);
	if (emulated == EMULATE_AGAIN) {
	advance = 0;
	} else if (emulated == EMULATE_FAIL) {
	advance = 0;
	printk(KERN_ERR "Couldn't emulate instruction 0x%08x "
	"(op %d xop %d)\n", inst, get_op(inst), get_xop(inst));
	kvmppc_core_queue_program(vcpu, 0);
	}
	}

	trace_kvm_ppc_instr(inst, kvmppc_get_pc(vcpu), emulated);

	/* Advance past emulated instruction. */
	if (advance)
	kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);

	return emulated;
	}