[PATCH] KVM: x86: Introduce segmented_write_std

[Steve Rutherford <srutherford@google.com>]

Introduces segemented_write_std.

Switches from emulated reads/writes to standard read/writes in fxsave,
fxrstor, sgdt, and sidt.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Steve Rutherford <srutherford@google.com>
---
 arch/x86/kvm/emulate.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 2b8349a2b14b..ad258aa0b302 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -819,6 +819,20 @@ static int segmented_read_std(struct x86_emulate_ctxt *ctxt,
 	return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception);
 }
 
+static int segmented_write_std(struct x86_emulate_ctxt *ctxt,
+			       struct segmented_address addr,
+			       void *data,
+			       unsigned int size)
+{
+	int rc;
+	ulong linear;
+
+	rc = linearize(ctxt, addr, size, true, &linear);
+	if (rc != X86EMUL_CONTINUE)
+		return rc;
+	return ctxt->ops->write_std(ctxt, linear, data, size, &ctxt->exception);
+}
+
 /*
  * Prefetch the remaining bytes of the instruction without crossing page
  * boundary if they are not in fetch_cache yet.
@@ -3686,8 +3700,8 @@ static int emulate_store_desc_ptr(struct x86_emulate_ctxt *ctxt,
 	}
 	/* Disable writeback. */
 	ctxt->dst.type = OP_NONE;
-	return segmented_write(ctxt, ctxt->dst.addr.mem,
-			       &desc_ptr, 2 + ctxt->op_bytes);
+	return segmented_write_std(ctxt, ctxt->dst.addr.mem,
+				   &desc_ptr, 2 + ctxt->op_bytes);
 }
 
 static int em_sgdt(struct x86_emulate_ctxt *ctxt)
@@ -3933,7 +3947,7 @@ static int em_fxsave(struct x86_emulate_ctxt *ctxt)
 	else
 		size = offsetof(struct fxregs_state, xmm_space[0]);
 
-	return segmented_write(ctxt, ctxt->memop.addr.mem, &fx_state, size);
+	return segmented_write_std(ctxt, ctxt->memop.addr.mem, &fx_state, size);
 }
 
 static int fxrstor_fixup(struct x86_emulate_ctxt *ctxt,
@@ -3975,7 +3989,7 @@ static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
 	if (rc != X86EMUL_CONTINUE)
 		return rc;
 
-	rc = segmented_read(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
+	rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
 	if (rc != X86EMUL_CONTINUE)
 		return rc;
 
-- 
2.11.0.390.gc69c2f50cf-goog