[PATCH v2 kvm-unit-tests 1/2] unify field names and definitions for GDT descriptors

[Paolo Bonzini <pbonzini@redhat.com>]

Use the same names and definitions (apart from the high base field)
for GDT descriptors in both 32-bit and 64-bit code.  The next patch
will also reuse gdt_entry_t in the 16-byte struct definition, for now
some duplication remains.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 lib/x86/desc.c   | 16 ++++++----------
 lib/x86/desc.h   | 28 +++++++++++++++++++++-------
 x86/taskswitch.c |  2 +-
 3 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/lib/x86/desc.c b/lib/x86/desc.c
index e7378c1..3d38565 100644
--- a/lib/x86/desc.c
+++ b/lib/x86/desc.c
@@ -285,17 +285,13 @@ void set_gdt_entry(int sel, u32 base,  u32 limit, u8 access, u8 gran)
 	int num = sel >> 3;
 
 	/* Setup the descriptor base address */
-	gdt32[num].base_low = (base & 0xFFFF);
-	gdt32[num].base_middle = (base >> 16) & 0xFF;
-	gdt32[num].base_high = (base >> 24) & 0xFF;
+	gdt32[num].base1 = (base & 0xFFFF);
+	gdt32[num].base2 = (base >> 16) & 0xFF;
+	gdt32[num].base3 = (base >> 24) & 0xFF;
 
-	/* Setup the descriptor limits */
-	gdt32[num].limit_low = (limit & 0xFFFF);
-	gdt32[num].granularity = ((limit >> 16) & 0x0F);
-
-	/* Finally, set up the granularity and access flags */
-	gdt32[num].granularity |= (gran & 0xF0);
-	gdt32[num].access = access;
+	/* Setup the descriptor limits, granularity and flags */
+	gdt32[num].limit1 = (limit & 0xFFFF);
+	gdt32[num].type_limit_flags = ((limit & 0xF0000) >> 8) | ((gran & 0xF0) << 8) | access;
 }
 
 void set_gdt_task_gate(u16 sel, u16 tss_sel)
diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index a6ffb38..0af37e3 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -164,14 +164,27 @@ typedef struct {
 } idt_entry_t;
 
 typedef struct {
-	u16 limit_low;
-	u16 base_low;
-	u8 base_middle;
-	u8 access;
-	u8 granularity;
-	u8 base_high;
-} gdt_entry_t;
+	uint16_t limit1;
+	uint16_t base1;
+	uint8_t  base2;
+	union {
+		uint16_t  type_limit_flags;      /* Type and limit flags */
+		struct {
+			uint16_t type:4;
+			uint16_t s:1;
+			uint16_t dpl:2;
+			uint16_t p:1;
+			uint16_t limit:4;
+			uint16_t avl:1;
+			uint16_t l:1;
+			uint16_t db:1;
+			uint16_t g:1;
+		} __attribute__((__packed__));
+	} __attribute__((__packed__));
+	uint8_t  base3;
+} __attribute__((__packed__)) gdt_entry_t;
 
+#ifdef __x86_64__
 struct segment_desc64 {
 	uint16_t limit1;
 	uint16_t base1;
@@ -194,6 +207,7 @@ struct segment_desc64 {
 	uint32_t base4;
 	uint32_t zero;
 } __attribute__((__packed__));
+#endif
 
 #define DESC_BUSY ((uint64_t) 1 << 41)
 
diff --git a/x86/taskswitch.c b/x86/taskswitch.c
index 889831e..b6b3451 100644
--- a/x86/taskswitch.c
+++ b/x86/taskswitch.c
@@ -21,7 +21,7 @@ fault_handler(unsigned long error_code)
 
 	tss.eip += 2;
 
-	gdt32[TSS_MAIN / 8].access &= ~2;
+	gdt32[TSS_MAIN / 8].type &= ~2;
 
 	set_gdt_task_gate(TSS_RETURN, tss_intr.prev);
 }
-- 
2.27.0