From 360eb3c5687e2df23e29e97878238765bfe6a756 Mon Sep 17 00:00:00 2001
From: Jiang Liu <jiang.liu@linux.intel.com>
Date: Mon, 6 Jan 2014 14:18:08 +0800
Subject: [PATCH] iommu/vt-d: use dedicated bitmap to track remapping entry
 allocation status

Currently Intel interrupt remapping drivers uses the "present" flag bit
in remapping entry to track whether an entry is allocated or not.
It works as follow:
1) allocate a remapping entry and set its "present" flag bit to 1
2) compose other fields for the entry
3) update the remapping entry with the composed value

The remapping hardware may access the entry between step 1 and step 3,
which then observers an entry with the "present" flag set but random
values in all other fields.

This patch introduces a dedicated bitmap to track remapping entry
allocation status instead of sharing the "present" flag with hardware,
thus eliminate the race window. It also simplifies the implementation.

Tested-and-reviewed-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
---
Reading git-format-patch failed