KVM: emulator: optimize "rep ins" handling

Optimize "rep ins" by allowing emulator to write back more than one
datum at a time. Introduce new operand type OP_MEM_STR which tells
writeback() that dst contains pointer to an array that should be written
back as opposite to just one data element.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 31 insertions, 6 deletions

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index e9e5675c0dfb..15f960c06ff7 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -213,8 +213,9 @@ typedef u32 __attribute__((vector_size(16))) sse128_t;
 
 /* Type, address-of, and value of an instruction's operand. */
 struct operand {
-        enum { OP_REG, OP_MEM, OP_IMM, OP_XMM, OP_MM, OP_NONE } type;
+        enum { OP_REG, OP_MEM, OP_MEM_STR, OP_IMM, OP_XMM, OP_MM, OP_NONE } type;
         unsigned int bytes;
+        unsigned int count;
         union {
                 unsigned long orig_val;
                 u64 orig_val64;
@@ -234,6 +235,7 @@ struct operand {
                 char valptr[sizeof(unsigned long) + 2];
                 sse128_t vec_val;
                 u64 mm_val;
+                void *data;
         };
 };
 
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 415f903facd3..39171cb307ea 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1301,8 +1301,15 @@ static int pio_in_emulated(struct x86_emulate_ctxt *ctxt,
                 rc->end = n * size;
         }
 
-        memcpy(dest, rc->data + rc->pos, size);
-        rc->pos += size;
+        if (ctxt->rep_prefix && !(ctxt->eflags & EFLG_DF)) {
+                ctxt->dst.data = rc->data + rc->pos;
+                ctxt->dst.type = OP_MEM_STR;
+                ctxt->dst.count = (rc->end - rc->pos) / size;
+                rc->pos = rc->end;
+        } else {
+                memcpy(dest, rc->data + rc->pos, size);
+                rc->pos += size;
+        }
         return 1;
 }
 
@@ -1546,6 +1553,14 @@ static int writeback(struct x86_emulate_ctxt *ctxt)
                 if (rc != X86EMUL_CONTINUE)
                         return rc;
                 break;
+        case OP_MEM_STR:
+                rc = segmented_write(ctxt,
+                                ctxt->dst.addr.mem,
+                                ctxt->dst.data,
+                                ctxt->dst.bytes * ctxt->dst.count);
+                if (rc != X86EMUL_CONTINUE)
+                        return rc;
+                break;
         case OP_XMM:
                 write_sse_reg(ctxt, &ctxt->dst.vec_val, ctxt->dst.addr.xmm);
                 break;
@@ -2793,7 +2808,7 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
 static void string_addr_inc(struct x86_emulate_ctxt *ctxt, int reg,
                 struct operand *op)
 {
-        int df = (ctxt->eflags & EFLG_DF) ? -1 : 1;
+        int df = (ctxt->eflags & EFLG_DF) ? -op->count : op->count;
 
         register_address_increment(ctxt, reg_rmw(ctxt, reg), df * op->bytes);
         op->addr.mem.ea = register_address(ctxt, reg_read(ctxt, reg));
@@ -3733,7 +3748,7 @@ static const struct opcode opcode_table[256] = {
         I(DstReg | SrcMem | ModRM | Src2Imm, em_imul_3op),
         I(SrcImmByte | Mov | Stack, em_push),
         I(DstReg | SrcMem | ModRM | Src2ImmByte, em_imul_3op),
-        I2bvIP(DstDI | SrcDX | Mov | String, em_in, ins, check_perm_in), /* insb, insw/insd */
+        I2bvIP(DstDI | SrcDX | Mov | String | Unaligned, em_in, ins, check_perm_in), /* insb, insw/insd */
         I2bvIP(SrcSI | DstDX | String, em_out, outs, check_perm_out), /* outsb, outsw/outsd */
         /* 0x70 - 0x7F */
         X16(D(SrcImmByte)),
@@ -3991,6 +4006,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
                         register_address(ctxt, reg_read(ctxt, VCPU_REGS_RDI));
                 op->addr.mem.seg = VCPU_SREG_ES;
                 op->val = 0;
+                op->count = 1;
                 break;
         case OpDX:
                 op->type = OP_REG;
@@ -4034,6 +4050,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
                         register_address(ctxt, reg_read(ctxt, VCPU_REGS_RSI));
                 op->addr.mem.seg = seg_override(ctxt);
                 op->val = 0;
+                op->count = 1;
                 break;
         case OpImmFAddr:
                 op->type = OP_IMM;
@@ -4575,8 +4592,14 @@ writeback:
                 string_addr_inc(ctxt, VCPU_REGS_RDI, &ctxt->dst);
 
         if (ctxt->rep_prefix && (ctxt->d & String)) {
+                unsigned int count;
                 struct read_cache *r = &ctxt->io_read;
-                register_address_increment(ctxt, reg_rmw(ctxt, VCPU_REGS_RCX), -1);
+                if ((ctxt->d & SrcMask) == SrcSI)
+                        count = ctxt->src.count;
+                else
+                        count = ctxt->dst.count;
+                register_address_increment(ctxt, reg_rmw(ctxt, VCPU_REGS_RCX),
+                                -count);
 
                 if (!string_insn_completed(ctxt)) {
                         /*