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Commit 9de41573 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
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KVM: x86 emulator: introduce read cache 



Introduce read cache which is needed for instruction that require more
then one exit to userspace. After returning from userspace the instruction
will be re-executed with cached read value.

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 1c11e713

arch/x86/include/asm/kvm_emulate.h

+1 −0
Original line number Diff line number Diff line
@@ -186,6 +186,7 @@ struct decode_cache { 
	unsigned long modrm_val;

	struct fetch_cache fetch;

	struct read_cache io_read;

	struct read_cache mem_read;

};



struct x86_emulate_ctxt {

arch/x86/kvm/emulate.c

+42 −14
Original line number Diff line number Diff line
@@ -1263,6 +1263,33 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;

}



static int read_emulated(struct x86_emulate_ctxt *ctxt,

			 struct x86_emulate_ops *ops,

			 unsigned long addr, void *dest, unsigned size)

{

	int rc;

	struct read_cache *mc = &ctxt->decode.mem_read;



	while (size) {

		int n = min(size, 8u);

		size -= n;

		if (mc->pos < mc->end)

			goto read_cached;



		rc = ops->read_emulated(addr, mc->data + mc->end, n, ctxt->vcpu);

		if (rc != X86EMUL_CONTINUE)

			return rc;

		mc->end += n;



	read_cached:

		memcpy(dest, mc->data + mc->pos, n);

		mc->pos += n;

		dest += n;

		addr += n;

	}

	return X86EMUL_CONTINUE;

}



static int pio_in_emulated(struct x86_emulate_ctxt *ctxt,

			   struct x86_emulate_ops *ops,

			   unsigned int size, unsigned short port,
@@ -1504,9 +1531,9 @@ static int emulate_pop(struct x86_emulate_ctxt *ctxt, 
	struct decode_cache *c = &ctxt->decode;

	int rc;



	rc = ops->read_emulated(register_address(c, ss_base(ctxt),

	rc = read_emulated(ctxt, ops, register_address(c, ss_base(ctxt),

						       c->regs[VCPU_REGS_RSP]),

				dest, len, ctxt->vcpu);

			   dest, len);

	if (rc != X86EMUL_CONTINUE)

		return rc;
@@ -2475,6 +2502,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
	int saved_dst_type = c->dst.type;



	ctxt->interruptibility = 0;

	ctxt->decode.mem_read.pos = 0;



	/* Shadow copy of register state. Committed on successful emulation.

	 * NOTE: we can copy them from vcpu as x86_decode_insn() doesn't
@@ -2529,20 +2557,16 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
	}



	if (c->src.type == OP_MEM) {

		rc = ops->read_emulated((unsigned long)c->src.ptr,

					&c->src.val,

					c->src.bytes,

					ctxt->vcpu);

		rc = read_emulated(ctxt, ops, (unsigned long)c->src.ptr,

					&c->src.val, c->src.bytes);

		if (rc != X86EMUL_CONTINUE)

			goto done;

		c->src.orig_val = c->src.val;

	}



	if (c->src2.type == OP_MEM) {

		rc = ops->read_emulated((unsigned long)c->src2.ptr,

					&c->src2.val,

					c->src2.bytes,

					ctxt->vcpu);

		rc = read_emulated(ctxt, ops, (unsigned long)c->src2.ptr,

					&c->src2.val, c->src2.bytes);

		if (rc != X86EMUL_CONTINUE)

			goto done;

	}
@@ -2553,8 +2577,8 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 


	if ((c->dst.type == OP_MEM) && !(c->d & Mov)) {

		/* optimisation - avoid slow emulated read if Mov */

		rc = ops->read_emulated((unsigned long)c->dst.ptr, &c->dst.val,

					c->dst.bytes, ctxt->vcpu);

		rc = read_emulated(ctxt, ops, (unsigned long)c->dst.ptr,

				   &c->dst.val, c->dst.bytes);

		if (rc != X86EMUL_CONTINUE)

			goto done;

	}
@@ -2981,7 +3005,11 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) 
		    (rc->end != 0 && rc->end == rc->pos))

			ctxt->restart = false;

	}



	/*

	 * reset read cache here in case string instruction is restared

	 * without decoding

	 */

	ctxt->decode.mem_read.end = 0;

	/* Commit shadow register state. */

	memcpy(ctxt->vcpu->arch.regs, c->regs, sizeof c->regs);

	kvm_rip_write(ctxt->vcpu, c->eip);