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: Gleb Natapov <gleb@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_emulate.h | 1 +
arch/x86/kvm/emulate.c | 56 +++++++++++++++++++++++++++---------
2 files changed, 43 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 0b2729b..288cbed 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -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 {
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5ac0bb4..6f40337 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1263,6 +1263,33 @@ done:
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),
- c->regs[VCPU_REGS_RSP]),
- dest, len, ctxt->vcpu);
+ rc = read_emulated(ctxt, ops, register_address(c, ss_base(ctxt),
+ c->regs[VCPU_REGS_RSP]),
+ 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 @@ writeback:
(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);
--
1.6.5
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