KVM: x86 emulator: Make emulate_push() store the value directly

PUSH emulation stores the value by calling writeback() after setting
the dst operand appropriately in emulate_push().

This writeback() using dst is not needed at all because we know the
target is the stack.  So this patch makes emulate_push() call, newly
introduced, segmented_write() directly.

By this, many inlined writeback()'s are removed.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 34 insertions, 53 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 1e0e3f8156f8..4f4d9bc6178a 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1345,17 +1345,19 @@ static inline int writeback(struct x86_emulate_ctxt *ctxt,
         return X86EMUL_CONTINUE;
 }
 
-static inline void emulate_push(struct x86_emulate_ctxt *ctxt,
-                                struct x86_emulate_ops *ops)
+static int emulate_push(struct x86_emulate_ctxt *ctxt,
+                        struct x86_emulate_ops *ops)
 {
         struct decode_cache *c = &ctxt->decode;
+        struct segmented_address addr;
 
-        c->dst.type  = OP_MEM;
-        c->dst.bytes = c->op_bytes;
-        c->dst.val = c->src.val;
         register_address_increment(c, &c->regs[VCPU_REGS_RSP], -c->op_bytes);
-        c->dst.addr.mem.ea = register_address(c, c->regs[VCPU_REGS_RSP]);
-        c->dst.addr.mem.seg = VCPU_SREG_SS;
+        addr.ea = register_address(c, c->regs[VCPU_REGS_RSP]);
+        addr.seg = VCPU_SREG_SS;
+
+        /* Disable writeback. */
+        c->dst.type = OP_NONE;
+        return segmented_write(ctxt, addr, &c->src.val, c->op_bytes);
 }
 
 static int emulate_pop(struct x86_emulate_ctxt *ctxt,
@@ -1417,14 +1419,14 @@ static int emulate_popf(struct x86_emulate_ctxt *ctxt,
         return rc;
 }
 
-static void emulate_push_sreg(struct x86_emulate_ctxt *ctxt,
-                              struct x86_emulate_ops *ops, int seg)
+static int emulate_push_sreg(struct x86_emulate_ctxt *ctxt,
+                             struct x86_emulate_ops *ops, int seg)
 {
         struct decode_cache *c = &ctxt->decode;
 
         c->src.val = ops->get_segment_selector(seg, ctxt->vcpu);
 
-        emulate_push(ctxt, ops);
+        return emulate_push(ctxt, ops);
 }
 
 static int emulate_pop_sreg(struct x86_emulate_ctxt *ctxt,
@@ -1454,18 +1456,13 @@ static int emulate_pusha(struct x86_emulate_ctxt *ctxt,
                 (reg == VCPU_REGS_RSP) ?
                 (c->src.val = old_esp) : (c->src.val = c->regs[reg]);
 
-                emulate_push(ctxt, ops);
-
-                rc = writeback(ctxt, ops);
+                rc = emulate_push(ctxt, ops);
                 if (rc != X86EMUL_CONTINUE)
                         return rc;
 
                 ++reg;
         }
 
-        /* Disable writeback. */
-        c->dst.type = OP_NONE;
-
         return rc;
 }
 
@@ -1503,27 +1500,22 @@ int emulate_int_real(struct x86_emulate_ctxt *ctxt,
 
         /* TODO: Add limit checks */
         c->src.val = ctxt->eflags;
-        emulate_push(ctxt, ops);
-        rc = writeback(ctxt, ops);
+        rc = emulate_push(ctxt, ops);
         if (rc != X86EMUL_CONTINUE)
                 return rc;
 
         ctxt->eflags &= ~(EFLG_IF | EFLG_TF | EFLG_AC);
 
         c->src.val = ops->get_segment_selector(VCPU_SREG_CS, ctxt->vcpu);
-        emulate_push(ctxt, ops);
-        rc = writeback(ctxt, ops);
+        rc = emulate_push(ctxt, ops);
         if (rc != X86EMUL_CONTINUE)
                 return rc;
 
         c->src.val = c->eip;
-        emulate_push(ctxt, ops);
-        rc = writeback(ctxt, ops);
+        rc = emulate_push(ctxt, ops);
         if (rc != X86EMUL_CONTINUE)
                 return rc;
 
-        c->dst.type = OP_NONE;
-
         ops->get_idt(&dt, ctxt->vcpu);
 
         eip_addr = dt.address + (irq << 2);
@@ -1713,6 +1705,7 @@ static inline int emulate_grp45(struct x86_emulate_ctxt *ctxt,
                                struct x86_emulate_ops *ops)
 {
         struct decode_cache *c = &ctxt->decode;
+        int rc = X86EMUL_CONTINUE;
 
         switch (c->modrm_reg) {
         case 0: /* inc */
@@ -1726,17 +1719,17 @@ static inline int emulate_grp45(struct x86_emulate_ctxt *ctxt,
                 old_eip = c->eip;
                 c->eip = c->src.val;
                 c->src.val = old_eip;
-                emulate_push(ctxt, ops);
+                rc = emulate_push(ctxt, ops);
                 break;
         }
         case 4: /* jmp abs */
                 c->eip = c->src.val;
                 break;
         case 6: /* push */
-                emulate_push(ctxt, ops);
+                rc = emulate_push(ctxt, ops);
                 break;
         }
-        return X86EMUL_CONTINUE;
+        return rc;
 }
 
 static inline int emulate_grp9(struct x86_emulate_ctxt *ctxt,
@@ -2380,7 +2373,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
                 c->op_bytes = c->ad_bytes = (next_tss_desc.type & 8) ? 4 : 2;
                 c->lock_prefix = 0;
                 c->src.val = (unsigned long) error_code;
-                emulate_push(ctxt, ops);
+                ret = emulate_push(ctxt, ops);
         }
 
         return ret;
@@ -2400,11 +2393,8 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
         rc = emulator_do_task_switch(ctxt, ops, tss_selector, reason,
                                      has_error_code, error_code);
 
-        if (rc == X86EMUL_CONTINUE) {
-                rc = writeback(ctxt, ops);
-                if (rc == X86EMUL_CONTINUE)
-                        ctxt->eip = c->eip;
-        }
+        if (rc == X86EMUL_CONTINUE)
+                ctxt->eip = c->eip;
 
         return (rc == X86EMUL_UNHANDLEABLE) ? EMULATION_FAILED : EMULATION_OK;
 }
@@ -2422,8 +2412,7 @@ static void string_addr_inc(struct x86_emulate_ctxt *ctxt, unsigned seg,
 
 static int em_push(struct x86_emulate_ctxt *ctxt)
 {
-        emulate_push(ctxt, ctxt->ops);
-        return X86EMUL_CONTINUE;
+        return emulate_push(ctxt, ctxt->ops);
 }
 
 static int em_das(struct x86_emulate_ctxt *ctxt)
@@ -2483,20 +2472,12 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
         memcpy(&c->eip, c->src.valptr, c->op_bytes);
 
         c->src.val = old_cs;
-        emulate_push(ctxt, ctxt->ops);
-        rc = writeback(ctxt, ctxt->ops);
+        rc = emulate_push(ctxt, ctxt->ops);
         if (rc != X86EMUL_CONTINUE)
                 return rc;
 
         c->src.val = old_eip;
-        emulate_push(ctxt, ctxt->ops);
-        rc = writeback(ctxt, ctxt->ops);
-        if (rc != X86EMUL_CONTINUE)
-                return rc;
-
-        c->dst.type = OP_NONE;
-
-        return X86EMUL_CONTINUE;
+        return emulate_push(ctxt, ctxt->ops);
 }
 
 static int em_ret_near_imm(struct x86_emulate_ctxt *ctxt)
@@ -3625,7 +3606,7 @@ special_insn:
                 emulate_2op_SrcV("add", c->src, c->dst, ctxt->eflags);
                 break;
         case 0x06:              /* push es */
-                emulate_push_sreg(ctxt, ops, VCPU_SREG_ES);
+                rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_ES);
                 break;
         case 0x07:              /* pop es */
                 rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_ES);
@@ -3635,14 +3616,14 @@ special_insn:
                 emulate_2op_SrcV("or", c->src, c->dst, ctxt->eflags);
                 break;
         case 0x0e:              /* push cs */
-                emulate_push_sreg(ctxt, ops, VCPU_SREG_CS);
+                rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_CS);
                 break;
         case 0x10 ... 0x15:
               adc:              /* adc */
                 emulate_2op_SrcV("adc", c->src, c->dst, ctxt->eflags);
                 break;
         case 0x16:              /* push ss */
-                emulate_push_sreg(ctxt, ops, VCPU_SREG_SS);
+                rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_SS);
                 break;
         case 0x17:              /* pop ss */
                 rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_SS);
@@ -3652,7 +3633,7 @@ special_insn:
                 emulate_2op_SrcV("sbb", c->src, c->dst, ctxt->eflags);
                 break;
         case 0x1e:              /* push ds */
-                emulate_push_sreg(ctxt, ops, VCPU_SREG_DS);
+                rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_DS);
                 break;
         case 0x1f:              /* pop ds */
                 rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_DS);
@@ -3789,7 +3770,7 @@ special_insn:
                 break;
         case 0x9c: /* pushf */
                 c->src.val =  (unsigned long) ctxt->eflags;
-                emulate_push(ctxt, ops);
+                rc = emulate_push(ctxt, ops);
                 break;
         case 0x9d: /* popf */
                 c->dst.type = OP_REG;
@@ -3864,7 +3845,7 @@ special_insn:
                 long int rel = c->src.val;
                 c->src.val = (unsigned long) c->eip;
                 jmp_rel(c, rel);
-                emulate_push(ctxt, ops);
+                rc = emulate_push(ctxt, ops);
                 break;
         }
         case 0xe9: /* jmp rel */
@@ -4157,7 +4138,7 @@ twobyte_insn:
                 c->dst.val = test_cc(c->b, ctxt->eflags);
                 break;
         case 0xa0:        /* push fs */
-                emulate_push_sreg(ctxt, ops, VCPU_SREG_FS);
+                rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_FS);
                 break;
         case 0xa1:       /* pop fs */
                 rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_FS);
@@ -4174,7 +4155,7 @@ twobyte_insn:
                 emulate_2op_cl("shld", c->src2, c->src, c->dst, ctxt->eflags);
                 break;
         case 0xa8:      /* push gs */
-                emulate_push_sreg(ctxt, ops, VCPU_SREG_GS);
+                rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_GS);
                 break;
         case 0xa9:      /* pop gs */
                 rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_GS);