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>

11 files changed, 140 insertions, 77 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index 20fb6f2890a0..a86ca652028c 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/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;
diff --git a/arch/powerpc/include/asm/kvm_booke.h b/arch/powerpc/include/asm/kvm_booke.h
index c7aed6105ff9..cbb19906ca36 100644
--- a/arch/powerpc/include/asm/kvm_booke.h
+++ b/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;
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index 246fb9a7df33..e38136304c1f 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/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;
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 31facfc1314b..37ca8a0897c3 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/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;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 2d154d9319b3..fa944a3abdf0 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/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;
 
         /*
diff --git a/arch/powerpc/kvm/book3s_paired_singles.c b/arch/powerpc/kvm/book3s_paired_singles.c
index 6c8011fd57e6..bfb8035314e3 100644
--- a/arch/powerpc/kvm/book3s_paired_singles.c
+++ b/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;
 
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index e76aec38ec21..b18f2d4fac59 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/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;
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index a06ef6b30258..50df5e3072cc 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/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;
diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index 79677d76d1a4..4385c14fca84 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/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)
diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
index da86d9ba3476..c5c64b6e7eb2 100644
--- a/arch/powerpc/kvm/emulate.c
+++ b/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
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index fe0257a8e335..cfa6cfabf4a3 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/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;