Commit 7b262e90 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
Browse files

KVM: x86 emulator: introduce pio in string read ahead. 



To optimize "rep ins" instruction do IO in big chunks ahead of time
instead of doing it only when required during instruction emulation.

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 5cd21917

arch/x86/include/asm/kvm_emulate.h

+7 −0
Original line number Diff line number Diff line
@@ -151,6 +151,12 @@ struct fetch_cache { 
	unsigned long end;

};



struct read_cache {

	u8 data[1024];

	unsigned long pos;

	unsigned long end;

};



struct decode_cache {

	u8 twobyte;

	u8 b;
@@ -178,6 +184,7 @@ struct decode_cache { 
	void *modrm_ptr;

	unsigned long modrm_val;

	struct fetch_cache fetch;

	struct read_cache io_read;

};



struct x86_emulate_ctxt {

arch/x86/kvm/emulate.c

+41 −5
Original line number Diff line number Diff line
@@ -1257,6 +1257,36 @@ done: 
	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;

}



static int pio_in_emulated(struct x86_emulate_ctxt *ctxt,

			   struct x86_emulate_ops *ops,

			   unsigned int size, unsigned short port,

			   void *dest)

{

	struct read_cache *rc = &ctxt->decode.io_read;



	if (rc->pos == rc->end) { /* refill pio read ahead */

		struct decode_cache *c = &ctxt->decode;

		unsigned int in_page, n;

		unsigned int count = c->rep_prefix ?

			address_mask(c, c->regs[VCPU_REGS_RCX]) : 1;

		in_page = (ctxt->eflags & EFLG_DF) ?

			offset_in_page(c->regs[VCPU_REGS_RDI]) :

			PAGE_SIZE - offset_in_page(c->regs[VCPU_REGS_RDI]);

		n = min(min(in_page, (unsigned int)sizeof(rc->data)) / size,

			count);

		if (n == 0)

			n = 1;

		rc->pos = rc->end = 0;

		if (!ops->pio_in_emulated(size, port, rc->data, n, ctxt->vcpu))

			return 0;

		rc->end = n * size;

	}



	memcpy(dest, rc->data + rc->pos, size);

	rc->pos += size;

	return 1;

}



static u32 desc_limit_scaled(struct desc_struct *desc)

{

	u32 limit = get_desc_limit(desc);
@@ -2622,8 +2652,8 @@ special_insn: 
			kvm_inject_gp(ctxt->vcpu, 0);

			goto done;

		}

		if (!ops->pio_in_emulated(c->dst.bytes, c->regs[VCPU_REGS_RDX],

					  &c->dst.val, 1, ctxt->vcpu))

		if (!pio_in_emulated(ctxt, ops, c->dst.bytes,

				     c->regs[VCPU_REGS_RDX], &c->dst.val))

			goto done; /* IO is needed, skip writeback */

		break;

	case 0x6e:		/* outsb */
@@ -2839,8 +2869,8 @@ special_insn: 
			kvm_inject_gp(ctxt->vcpu, 0);

			goto done;

		}

		if (!ops->pio_in_emulated(c->dst.bytes, c->src.val,

					  &c->dst.val, 1, ctxt->vcpu))

		if (!pio_in_emulated(ctxt, ops, c->dst.bytes, c->src.val,

				     &c->dst.val))

			goto done; /* IO is needed */

		break;

	case 0xee: /* out al,dx */
@@ -2928,8 +2958,14 @@ writeback: 
		string_addr_inc(ctxt, es_base(ctxt), VCPU_REGS_RDI, &c->dst);



	if (c->rep_prefix && (c->d & String)) {

		struct read_cache *rc = &ctxt->decode.io_read;

		register_address_increment(c, &c->regs[VCPU_REGS_RCX], -1);

		if (!(c->regs[VCPU_REGS_RCX] & 0x3ff))

		/*

		 * Re-enter guest when pio read ahead buffer is empty or,

		 * if it is not used, after each 1024 iteration.

		 */

		if ((rc->end == 0 && !(c->regs[VCPU_REGS_RCX] & 0x3ff)) ||

		    (rc->end != 0 && rc->end == rc->pos))

			ctxt->restart = false;

	}