[PATCH kvm-unit-tests 1/9] x86: cleanup handling of 16-byte GDT descriptors

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

Look them up using a gdt_entry_t pointer, so that the address of
the descriptor is correct even for "odd" selectors (e.g. 0x98).
Rename the struct from segment_desc64 to system_desc64,
highlighting that it is only used in the case of S=0 (system
descriptor).  Rename the "limit" bitfield to "limit2", matching
the convention used for the various parts of the base field.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 lib/x86/desc.h         |  4 ++--
 x86/svm_tests.c        | 12 ++++++------
 x86/vmware_backdoors.c |  8 ++++----
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index a6ffb38..1755486 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -172,7 +172,7 @@ typedef struct {
 	u8 base_high;
 } gdt_entry_t;
 
-struct segment_desc64 {
+struct system_desc64 {
 	uint16_t limit1;
 	uint16_t base1;
 	uint8_t  base2;
@@ -183,7 +183,7 @@ struct segment_desc64 {
 			uint16_t s:1;
 			uint16_t dpl:2;
 			uint16_t p:1;
-			uint16_t limit:4;
+			uint16_t limit2:4;
 			uint16_t avl:1;
 			uint16_t l:1;
 			uint16_t db:1;
diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index afdd359..2fdb0dc 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -1876,22 +1876,22 @@ static bool reg_corruption_check(struct svm_test *test)
 static void get_tss_entry(void *data)
 {
     struct descriptor_table_ptr gdt;
-    struct segment_desc64 *gdt_table;
-    struct segment_desc64 *tss_entry;
+    gdt_entry_t *gdt_table;
+    struct system_desc64 *tss_entry;
     u16 tr = 0;
 
     sgdt(&gdt);
     tr = str();
-    gdt_table = (struct segment_desc64 *) gdt.base;
-    tss_entry = &gdt_table[tr / sizeof(struct segment_desc64)];
-    *((struct segment_desc64 **)data) = tss_entry;
+    gdt_table = (gdt_entry_t *) gdt.base;
+    tss_entry = (struct system_desc64 *) &gdt_table[tr / 8];
+    *((struct system_desc64 **)data) = tss_entry;
 }
 
 static int orig_cpu_count;
 
 static void init_startup_prepare(struct svm_test *test)
 {
-    struct segment_desc64 *tss_entry;
+    struct system_desc64 *tss_entry;
     int i;
 
     on_cpu(1, get_tss_entry, &tss_entry);
diff --git a/x86/vmware_backdoors.c b/x86/vmware_backdoors.c
index b4902a9..b1433cd 100644
--- a/x86/vmware_backdoors.c
+++ b/x86/vmware_backdoors.c
@@ -133,8 +133,8 @@ struct fault_test vmware_backdoor_tests[] = {
 static void set_tss_ioperm(void)
 {
 	struct descriptor_table_ptr gdt;
-	struct segment_desc64 *gdt_table;
-	struct segment_desc64 *tss_entry;
+	gdt_entry_t *gdt_table;
+	struct system_desc64 *tss_entry;
 	u16 tr = 0;
 	tss64_t *tss;
 	unsigned char *ioperm_bitmap;
@@ -142,8 +142,8 @@ static void set_tss_ioperm(void)
 
 	sgdt(&gdt);
 	tr = str();
-	gdt_table = (struct segment_desc64 *) gdt.base;
-	tss_entry = &gdt_table[tr / sizeof(struct segment_desc64)];
+	gdt_table = (gdt_entry_t *) gdt.base;
+	tss_entry = (struct system_desc64 *) &gdt_table[tr / 8];
 	tss_base = ((uint64_t) tss_entry->base1 |
 			((uint64_t) tss_entry->base2 << 16) |
 			((uint64_t) tss_entry->base3 << 24) |
-- 
2.27.0