KVM: PPC: Allow kvmppc_get_last_inst() to fail

On book3e, guest last instruction is read on the exit path using load
external pid (lwepx) dedicated instruction. This load operation may fail
due to TLB eviction and execute-but-not-read entries.

This patch lay down the path for an alternative solution to read the guest
last instruction, by allowing kvmppc_get_lat_inst() function to fail.
Architecture specific implmentations of kvmppc_load_last_inst() may read
last guest instruction and instruct the emulation layer to re-execute the
guest in case of failure.

Make kvmppc_get_last_inst() definition common between architectures.

Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/include/asm/kvm_book3s.h

@@ -276,32 +276,6 @@ static inline bool kvmppc_need_byteswap(struct kvm_vcpu *vcpu)
 	return (kvmppc_get_msr(vcpu) & MSR_LE) != (MSR_KERNEL & MSR_LE);
 }
 
-static inline u32 kvmppc_get_last_inst_internal(struct kvm_vcpu *vcpu, ulong pc)
-{
-	/* Load the instruction manually if it failed to do so in the
-	 * exit path */
-	if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED)
-		kvmppc_ld(vcpu, &pc, sizeof(u32), &vcpu->arch.last_inst, false);
-
-	return kvmppc_need_byteswap(vcpu) ? swab32(vcpu->arch.last_inst) :
-		vcpu->arch.last_inst;
-}
-
-static inline u32 kvmppc_get_last_inst(struct kvm_vcpu *vcpu)
-{
-	return kvmppc_get_last_inst_internal(vcpu, kvmppc_get_pc(vcpu));
-}
-
-/*
- * Like kvmppc_get_last_inst(), but for fetching a sc instruction.
- * Because the sc instruction sets SRR0 to point to the following
- * instruction, we have to fetch from pc - 4.
- */
-static inline u32 kvmppc_get_last_sc(struct kvm_vcpu *vcpu)
-{
-	return kvmppc_get_last_inst_internal(vcpu, kvmppc_get_pc(vcpu) - 4);
-}
-
 static inline ulong kvmppc_get_fault_dar(struct kvm_vcpu *vcpu)
 {
 	return vcpu->arch.fault_dar;

arch/powerpc/include/asm/kvm_booke.h

@@ -69,11 +69,6 @@ static inline bool kvmppc_need_byteswap(struct kvm_vcpu *vcpu)
 	return false;
 }
 
-static inline u32 kvmppc_get_last_inst(struct kvm_vcpu *vcpu)
-{
-	return vcpu->arch.last_inst;
-}
-
 static inline void kvmppc_set_ctr(struct kvm_vcpu *vcpu, ulong val)
 {
 	vcpu->arch.ctr = val;

arch/powerpc/include/asm/kvm_ppc.h

@@ -47,6 +47,11 @@ enum emulation_result {
 	EMULATE_EXIT_USER,    /* emulation requires exit to user-space */
 };
 
+enum instruction_type {
+	INST_GENERIC,
+	INST_SC,		/* system call */
+};
+
 extern int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
 extern int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
 extern void kvmppc_handler_highmem(void);
@@ -62,6 +67,9 @@ extern int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			       u64 val, unsigned int bytes,
 			       int is_default_endian);
 
+extern int kvmppc_load_last_inst(struct kvm_vcpu *vcpu,
+				 enum instruction_type type, u32 *inst);
+
 extern int kvmppc_emulate_instruction(struct kvm_run *run,
                                       struct kvm_vcpu *vcpu);
 extern int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu);
@@ -234,6 +242,29 @@ struct kvmppc_ops {
 extern struct kvmppc_ops *kvmppc_hv_ops;
 extern struct kvmppc_ops *kvmppc_pr_ops;
 
+static inline int kvmppc_get_last_inst(struct kvm_vcpu *vcpu,
+					enum instruction_type type, u32 *inst)
+{
+	int ret = EMULATE_DONE;
+	u32 fetched_inst;
+
+	/* Load the instruction manually if it failed to do so in the
+	 * exit path */
+	if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED)
+		ret = kvmppc_load_last_inst(vcpu, type, &vcpu->arch.last_inst);
+
+	/*  Write fetch_failed unswapped if the fetch failed */
+	if (ret == EMULATE_DONE)
+		fetched_inst = kvmppc_need_byteswap(vcpu) ?
+				swab32(vcpu->arch.last_inst) :
+				vcpu->arch.last_inst;
+	else
+		fetched_inst = vcpu->arch.last_inst;
+
+	*inst = fetched_inst;
+	return ret;
+}
+
 static inline bool is_kvmppc_hv_enabled(struct kvm *kvm)
 {
 	return kvm->arch.kvm_ops == kvmppc_hv_ops;

arch/powerpc/kvm/book3s.c

@@ -488,6 +488,23 @@ mmio:
 }
 EXPORT_SYMBOL_GPL(kvmppc_ld);
 
+int kvmppc_load_last_inst(struct kvm_vcpu *vcpu, enum instruction_type type,
+					 u32 *inst)
+{
+	ulong pc = kvmppc_get_pc(vcpu);
+	int r;
+
+	if (type == INST_SC)
+		pc -= 4;
+
+	r = kvmppc_ld(vcpu, &pc, sizeof(u32), inst, false);
+	if (r == EMULATE_DONE)
+		return r;
+	else
+		return EMULATE_AGAIN;
+}
+EXPORT_SYMBOL_GPL(kvmppc_load_last_inst);
+
 int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 {
 	return 0;

arch/powerpc/kvm/book3s_64_mmu_hv.c

@@ -530,21 +530,14 @@ static int instruction_is_store(unsigned int instr)
 static int kvmppc_hv_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu,
 				  unsigned long gpa, gva_t ea, int is_store)
 {
-	int ret;
 	u32 last_inst;
-	unsigned long srr0 = kvmppc_get_pc(vcpu);
 
-	/* We try to load the last instruction.  We don't let
-	 * emulate_instruction do it as it doesn't check what
-	 * kvmppc_ld returns.
+	/*
 	 * If we fail, we just return to the guest and try executing it again.
 	 */
-	if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED) {
-		ret = kvmppc_ld(vcpu, &srr0, sizeof(u32), &last_inst, false);
-		if (ret != EMULATE_DONE || last_inst == KVM_INST_FETCH_FAILED)
-			return RESUME_GUEST;
-		vcpu->arch.last_inst = last_inst;
-	}
+	if (kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=
+		EMULATE_DONE)
+		return RESUME_GUEST;
 
 	/*
 	 * WARNING: We do not know for sure whether the instruction we just
@@ -558,7 +551,7 @@ static int kvmppc_hv_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	 * we just return and retry the instruction.
 	 */
 
-	if (instruction_is_store(kvmppc_get_last_inst(vcpu)) != !!is_store)
+	if (instruction_is_store(last_inst) != !!is_store)
 		return RESUME_GUEST;
 
 	/*

arch/powerpc/kvm/book3s_paired_singles.c

@@ -639,26 +639,36 @@ static int kvmppc_ps_one_in(struct kvm_vcpu *vcpu, bool rc,
 
 int kvmppc_emulate_paired_single(struct kvm_run *run, struct kvm_vcpu *vcpu)
 {
-	u32 inst = kvmppc_get_last_inst(vcpu);
+	u32 inst;
 	enum emulation_result emulated = EMULATE_DONE;
+	int ax_rd, ax_ra, ax_rb, ax_rc;
+	short full_d;
+	u64 *fpr_d, *fpr_a, *fpr_b, *fpr_c;
 
-	int ax_rd = inst_get_field(inst, 6, 10);
-	int ax_ra = inst_get_field(inst, 11, 15);
-	int ax_rb = inst_get_field(inst, 16, 20);
-	int ax_rc = inst_get_field(inst, 21, 25);
-	short full_d = inst_get_field(inst, 16, 31);
-
-	u64 *fpr_d = &VCPU_FPR(vcpu, ax_rd);
-	u64 *fpr_a = &VCPU_FPR(vcpu, ax_ra);
-	u64 *fpr_b = &VCPU_FPR(vcpu, ax_rb);
-	u64 *fpr_c = &VCPU_FPR(vcpu, ax_rc);
-
-	bool rcomp = (inst & 1) ? true : false;
-	u32 cr = kvmppc_get_cr(vcpu);
+	bool rcomp;
+	u32 cr;
 #ifdef DEBUG
 	int i;
 #endif
 
+	emulated = kvmppc_get_last_inst(vcpu, INST_GENERIC, &inst);
+	if (emulated != EMULATE_DONE)
+		return emulated;
+
+	ax_rd = inst_get_field(inst, 6, 10);
+	ax_ra = inst_get_field(inst, 11, 15);
+	ax_rb = inst_get_field(inst, 16, 20);
+	ax_rc = inst_get_field(inst, 21, 25);
+	full_d = inst_get_field(inst, 16, 31);
+
+	fpr_d = &VCPU_FPR(vcpu, ax_rd);
+	fpr_a = &VCPU_FPR(vcpu, ax_ra);
+	fpr_b = &VCPU_FPR(vcpu, ax_rb);
+	fpr_c = &VCPU_FPR(vcpu, ax_rc);
+
+	rcomp = (inst & 1) ? true : false;
+	cr = kvmppc_get_cr(vcpu);
+
 	if (!kvmppc_inst_is_paired_single(vcpu, inst))
 		return EMULATE_FAIL;
 

arch/powerpc/kvm/book3s_pr.c

@@ -1018,15 +1018,24 @@ int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	{
 		enum emulation_result er;
 		ulong flags;
+		u32 last_inst;
+		int emul;
 
 program_interrupt:
 		flags = vcpu->arch.shadow_srr1 & 0x1f0000ull;
 
+		emul = kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst);
+		if (emul != EMULATE_DONE) {
+			r = RESUME_GUEST;
+			break;
+		}
+
 		if (kvmppc_get_msr(vcpu) & MSR_PR) {
 #ifdef EXIT_DEBUG
-			printk(KERN_INFO "Userspace triggered 0x700 exception at 0x%lx (0x%x)\n", kvmppc_get_pc(vcpu), kvmppc_get_last_inst(vcpu));
+			pr_info("Userspace triggered 0x700 exception at\n 0x%lx (0x%x)\n",
+				kvmppc_get_pc(vcpu), last_inst);
 #endif
-			if ((kvmppc_get_last_inst(vcpu) & 0xff0007ff) !=
+			if ((last_inst & 0xff0007ff) !=
 			    (INS_DCBZ & 0xfffffff7)) {
 				kvmppc_core_queue_program(vcpu, flags);
 				r = RESUME_GUEST;
@@ -1045,7 +1054,7 @@ program_interrupt:
 			break;
 		case EMULATE_FAIL:
 			printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",
-			       __func__, kvmppc_get_pc(vcpu), kvmppc_get_last_inst(vcpu));
+			       __func__, kvmppc_get_pc(vcpu), last_inst);
 			kvmppc_core_queue_program(vcpu, flags);
 			r = RESUME_GUEST;
 			break;
@@ -1062,8 +1071,23 @@ program_interrupt:
 		break;
 	}
 	case BOOK3S_INTERRUPT_SYSCALL:
+	{
+		u32 last_sc;
+		int emul;
+
+		/* Get last sc for papr */
+		if (vcpu->arch.papr_enabled) {
+			/* The sc instuction points SRR0 to the next inst */
+			emul = kvmppc_get_last_inst(vcpu, INST_SC, &last_sc);
+			if (emul != EMULATE_DONE) {
+				kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) - 4);
+				r = RESUME_GUEST;
+				break;
+			}
+		}
+
 		if (vcpu->arch.papr_enabled &&
-		    (kvmppc_get_last_sc(vcpu) == 0x44000022) &&
+		    (last_sc == 0x44000022) &&
 		    !(kvmppc_get_msr(vcpu) & MSR_PR)) {
 			/* SC 1 papr hypercalls */
 			ulong cmd = kvmppc_get_gpr(vcpu, 3);
@@ -1108,21 +1132,19 @@ program_interrupt:
 			r = RESUME_GUEST;
 		}
 		break;
+	}
 	case BOOK3S_INTERRUPT_FP_UNAVAIL:
 	case BOOK3S_INTERRUPT_ALTIVEC:
 	case BOOK3S_INTERRUPT_VSX:
 	{
 		int ext_msr = 0;
 		int emul;
-		ulong pc;
 		u32 last_inst;
 
 		if (vcpu->arch.hflags & BOOK3S_HFLAG_PAIRED_SINGLE) {
 			/* Do paired single instruction emulation */
-			pc = kvmppc_get_pc(vcpu);
-			last_inst = kvmppc_get_last_inst(vcpu);
-			emul = kvmppc_ld(vcpu, &pc, sizeof(u32), &last_inst,
-					 false);
+			emul = kvmppc_get_last_inst(vcpu, INST_GENERIC,
+						    &last_inst);
 			if (emul == EMULATE_DONE)
 				goto program_interrupt;
 			else
@@ -1151,9 +1173,8 @@ program_interrupt:
 	}
 	case BOOK3S_INTERRUPT_ALIGNMENT:
 	{
-		ulong pc = kvmppc_get_pc(vcpu);
-		u32 last_inst = kvmppc_get_last_inst(vcpu);
-		int emul = kvmppc_ld(vcpu, &pc, sizeof(u32), &last_inst, false);
+		u32 last_inst;
+		int emul = kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst);
 
 		if (emul == EMULATE_DONE) {
 			u32 dsisr;

arch/powerpc/kvm/booke.c

@@ -702,6 +702,9 @@ static int emulation_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
 		 * they were actually modified by emulation. */
 		return RESUME_GUEST_NV;
 
+	case EMULATE_AGAIN:
+		return RESUME_GUEST;
+
 	case EMULATE_DO_DCR:
 		run->exit_reason = KVM_EXIT_DCR;
 		return RESUME_HOST;

arch/powerpc/kvm/e500_mmu_host.c

@@ -610,6 +610,12 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 eaddr, gpa_t gpaddr,
 	}
 }
 
+int kvmppc_load_last_inst(struct kvm_vcpu *vcpu, enum instruction_type type,
+			  u32 *instr)
+{
+	return EMULATE_AGAIN;
+}
+
 /************* MMU Notifiers *************/
 
 int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)

arch/powerpc/kvm/emulate.c

@@ -224,19 +224,25 @@ static int kvmppc_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
  * 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;
+	u32 inst;
+	int ra, rs, rt, sprn;
+	enum emulation_result emulated;
 	int advance = 1;
 
 	/* this default type might be overwritten by subcategories */
 	kvmppc_set_exit_type(vcpu, EMULATED_INST_EXITS);
 
+	emulated = kvmppc_get_last_inst(vcpu, false, &inst);
+	if (emulated != EMULATE_DONE)
+		return emulated;
+
 	pr_debug("Emulating opcode %d / %d\n", get_op(inst), get_xop(inst));
 
+	ra = get_ra(inst);
+	rs = get_rs(inst);
+	rt = get_rt(inst);
+	sprn = get_sprn(inst);
+
 	switch (get_op(inst)) {
 	case OP_TRAP:
 #ifdef CONFIG_PPC_BOOK3S

arch/powerpc/kvm/powerpc.c

@@ -280,6 +280,9 @@ int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu)
 		 * actually modified. */
 		r = RESUME_GUEST_NV;
 		break;
+	case EMULATE_AGAIN:
+		r = RESUME_GUEST;
+		break;
 	case EMULATE_DO_MMIO:
 		run->exit_reason = KVM_EXIT_MMIO;
 		/* We must reload nonvolatiles because "update" load/store
@@ -289,11 +292,15 @@ int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu)
 		r = RESUME_HOST_NV;
 		break;
 	case EMULATE_FAIL:
+	{
+		u32 last_inst;
+
+		kvmppc_get_last_inst(vcpu, false, &last_inst);
 		/* XXX Deliver Program interrupt to guest. */
-		printk(KERN_EMERG "%s: emulation failed (%08x)\n", __func__,
-		       kvmppc_get_last_inst(vcpu));
+		pr_emerg("%s: emulation failed (%08x)\n", __func__, last_inst);
 		r = RESUME_HOST;
 		break;
+	}
 	default:
 		WARN_ON(1);
 		r = RESUME_GUEST;