[PATCH 1/1] x86/iommu: use bit structures for context_entry

[Li, Zhen-Hua]

There is a structure named context_entry used by intel iommu, and there
are some bit operations on it. Use bit structure may make these operations
easy.
Also the function context_set_address_root may cause problem because it uses
 |= operation, not set the new value. And this patch can fix it.

Signed-off-by: Li, Zhen-Hua <zhen-h...@hp.com>
---
 drivers/iommu/intel-iommu.c | 37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 43b9bfe..65cd480 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -221,47 +221,64 @@ get_context_addr_from_root(struct root_entry *root)
  * 8-23: domain id
  */
 struct context_entry {
-       u64 lo;
-       u64 hi;
+       union {
+               struct {
+                       u64     present:1,
+                               fpd:1,
+                               translation_type:2,
+                               reserved_l:8,
+                               asr:52;
+               };
+               u64 lo;
+       };
+       union {
+               struct {
+                       u64     aw:3,
+                               avail:4,
+                               reserved_h1:1,
+                               did:16,
+                               reserved_h2:40;
+               };
+               u64 hi;
+       };
 };
 
 static inline bool context_present(struct context_entry *context)
 {
-       return (context->lo & 1);
+       return context->present;
 }
 static inline void context_set_present(struct context_entry *context)
 {
-       context->lo |= 1;
+       context->present = 1;
 }
 
 static inline void context_set_fault_enable(struct context_entry *context)
 {
-       context->lo &= (((u64)-1) << 2) | 1;
+       context->fpd = 1;
 }
 
 static inline void context_set_translation_type(struct context_entry *context,
                                                unsigned long value)
 {
-       context->lo &= (((u64)-1) << 4) | 3;
-       context->lo |= (value & 3) << 2;
+       context->translation_type = value;
 }
 
 static inline void context_set_address_root(struct context_entry *context,
                                            unsigned long value)
 {
-       context->lo |= value & VTD_PAGE_MASK;
+       context->asr = value >> VTD_PAGE_SHIFT
 }
 
 static inline void context_set_address_width(struct context_entry *context,
                                             unsigned long value)
 {
-       context->hi |= value & 7;
+       context->aw  = value;
 }
 
 static inline void context_set_domain_id(struct context_entry *context,
                                         unsigned long value)
 {
-       context->hi |= (value & ((1 << 16) - 1)) << 8;
+       context->did = value;
 }
 
 static inline void context_clear_entry(struct context_entry *context)
-- 
1.8.4.3

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