[PATCH v2 kvm-unit-tests 2/2] replace tss_descr global with a function

[Paolo Bonzini <pbonzini@redhat.com>]

tss_descr is declared as a struct descriptor_table_ptr but it is actualy
pointing to an _entry_ in the GDT.  Also it is different per CPU, but
tss_descr does not recognize that.  Fix both by reusing the code
(already present e.g. in the vmware_backdoors test) that extracts
the base from the GDT entry; and also provide a helper to retrieve
the limit, which is needed in vmx.c.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 lib/x86/desc.c         | 22 ++++++++++++++++++++++
 lib/x86/desc.h         | 28 +++++++---------------------
 x86/cstart64.S         |  1 -
 x86/svm_tests.c        | 15 +++------------
 x86/vmware_backdoors.c | 22 ++++++----------------
 x86/vmx.c              |  9 +++++----
 6 files changed, 43 insertions(+), 54 deletions(-)

diff --git a/lib/x86/desc.c b/lib/x86/desc.c
index 3d38565..cfda2b2 100644
--- a/lib/x86/desc.c
+++ b/lib/x86/desc.c
@@ -409,3 +409,25 @@ void __set_exception_jmpbuf(jmp_buf *addr)
 {
 	exception_jmpbuf = addr;
 }
+
+gdt_entry_t *get_tss_descr(void)
+{
+	struct descriptor_table_ptr gdt_ptr;
+	gdt_entry_t *gdt;
+
+	sgdt(&gdt_ptr);
+	gdt = (gdt_entry_t *)gdt_ptr.base;
+	return &gdt[str() / 8];
+}
+
+unsigned long get_gdt_entry_base(gdt_entry_t *entry)
+{
+	unsigned long base;
+	base = entry->base1 | ((u32)entry->base2 << 16) | ((u32)entry->base3 << 24);
+#ifdef __x86_64__
+	if (!entry->s) {
+	    base |= (u64)((gdt_entry16_t *)entry)->base4 << 32;
+	}
+#endif
+	return base;
+}
diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index 0af37e3..e8a6c21 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -185,31 +185,14 @@ typedef struct {
 } __attribute__((__packed__)) gdt_entry_t;
 
 #ifdef __x86_64__
-struct segment_desc64 {
-	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;
+typedef struct {
+	gdt_entry_t common;
 	uint32_t base4;
 	uint32_t zero;
-} __attribute__((__packed__));
+} __attribute__((__packed__)) gdt_entry16_t;
 #endif
 
-#define DESC_BUSY ((uint64_t) 1 << 41)
+#define DESC_BUSY 2
 
 extern idt_entry_t boot_idt[256];
 
@@ -253,4 +236,7 @@ static inline void *get_idt_addr(idt_entry_t *entry)
 	return (void *)addr;
 }
 
+extern gdt_entry_t *get_tss_descr(void);
+extern unsigned long get_gdt_entry_base(gdt_entry_t *entry);
+
 #endif
diff --git a/x86/cstart64.S b/x86/cstart64.S
index 5c6ad38..cf38bae 100644
--- a/x86/cstart64.S
+++ b/x86/cstart64.S
@@ -4,7 +4,6 @@
 .globl boot_idt
 
 .globl idt_descr
-.globl tss_descr
 .globl gdt64_desc
 .globl online_cpus
 .globl cpu_online_count
diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index afdd359..8ad6122 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -1875,23 +1875,14 @@ 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;
-    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_entry_t **)data) = get_tss_descr();
 }
 
 static int orig_cpu_count;
 
 static void init_startup_prepare(struct svm_test *test)
 {
-    struct segment_desc64 *tss_entry;
+    gdt_entry_t *tss_entry;
     int i;
 
     on_cpu(1, get_tss_entry, &tss_entry);
@@ -1905,7 +1896,7 @@ static void init_startup_prepare(struct svm_test *test)
 
     --cpu_online_count;
 
-    *(uint64_t *)tss_entry &= ~DESC_BUSY;
+    tss_entry->type &= ~DESC_BUSY;
 
     apic_icr_write(APIC_DEST_PHYSICAL | APIC_DM_STARTUP, id_map[1]);
 
diff --git a/x86/vmware_backdoors.c b/x86/vmware_backdoors.c
index b4902a9..bc10020 100644
--- a/x86/vmware_backdoors.c
+++ b/x86/vmware_backdoors.c
@@ -132,23 +132,13 @@ 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;
-	u16 tr = 0;
+	gdt_entry_t *tss_entry;
 	tss64_t *tss;
 	unsigned char *ioperm_bitmap;
-	uint64_t tss_base;
-
-	sgdt(&gdt);
-	tr = str();
-	gdt_table = (struct segment_desc64 *) gdt.base;
-	tss_entry = &gdt_table[tr / sizeof(struct segment_desc64)];
-	tss_base = ((uint64_t) tss_entry->base1 |
-			((uint64_t) tss_entry->base2 << 16) |
-			((uint64_t) tss_entry->base3 << 24) |
-			((uint64_t) tss_entry->base4 << 32));
-	tss = (tss64_t *)tss_base;
+	u16 tr = str();
+
+	tss_entry = get_tss_descr();
+	tss = (tss64_t *)get_gdt_entry_base(tss_entry);
 	tss->iomap_base = sizeof(*tss);
 	ioperm_bitmap = ((unsigned char *)tss+tss->iomap_base);
 
@@ -157,7 +147,7 @@ static void set_tss_ioperm(void)
 		1 << (RANDOM_IO_PORT % 8);
 	ioperm_bitmap[VMWARE_BACKDOOR_PORT / 8] |=
 		1 << (VMWARE_BACKDOOR_PORT % 8);
-	*(uint64_t *)tss_entry &= ~DESC_BUSY;
+	tss_entry->type &= ~DESC_BUSY;
 
 	/* Update TSS */
 	ltr(tr);
diff --git a/x86/vmx.c b/x86/vmx.c
index 20dc677..063f96a 100644
--- a/x86/vmx.c
+++ b/x86/vmx.c
@@ -75,7 +75,6 @@ union vmx_ept_vpid  ept_vpid;
 
 extern struct descriptor_table_ptr gdt64_desc;
 extern struct descriptor_table_ptr idt_descr;
-extern struct descriptor_table_ptr tss_descr;
 extern void *vmx_return;
 extern void *entry_sysenter;
 extern void *guest_entry;
@@ -1275,7 +1274,7 @@ static void init_vmcs_host(void)
 	vmcs_write(HOST_SEL_FS, KERNEL_DS);
 	vmcs_write(HOST_SEL_GS, KERNEL_DS);
 	vmcs_write(HOST_SEL_TR, TSS_MAIN);
-	vmcs_write(HOST_BASE_TR, tss_descr.base);
+	vmcs_write(HOST_BASE_TR, get_gdt_entry_base(get_tss_descr()));
 	vmcs_write(HOST_BASE_GDTR, gdt64_desc.base);
 	vmcs_write(HOST_BASE_IDTR, idt_descr.base);
 	vmcs_write(HOST_BASE_FS, 0);
@@ -1291,6 +1290,8 @@ static void init_vmcs_host(void)
 
 static void init_vmcs_guest(void)
 {
+	gdt_entry_t *tss_descr = get_tss_descr();
+
 	/* 26.3 CHECKING AND LOADING GUEST STATE */
 	ulong guest_cr0, guest_cr4, guest_cr3;
 	/* 26.3.1.1 */
@@ -1331,7 +1332,7 @@ static void init_vmcs_guest(void)
 	vmcs_write(GUEST_BASE_DS, 0);
 	vmcs_write(GUEST_BASE_FS, 0);
 	vmcs_write(GUEST_BASE_GS, 0);
-	vmcs_write(GUEST_BASE_TR, tss_descr.base);
+	vmcs_write(GUEST_BASE_TR, get_gdt_entry_base(tss_descr));
 	vmcs_write(GUEST_BASE_LDTR, 0);
 
 	vmcs_write(GUEST_LIMIT_CS, 0xFFFFFFFF);
@@ -1341,7 +1342,7 @@ static void init_vmcs_guest(void)
 	vmcs_write(GUEST_LIMIT_FS, 0xFFFFFFFF);
 	vmcs_write(GUEST_LIMIT_GS, 0xFFFFFFFF);
 	vmcs_write(GUEST_LIMIT_LDTR, 0xffff);
-	vmcs_write(GUEST_LIMIT_TR, tss_descr.limit);
+	vmcs_write(GUEST_LIMIT_TR, 0x67);
 
 	vmcs_write(GUEST_AR_CS, 0xa09b);
 	vmcs_write(GUEST_AR_DS, 0xc093);
-- 
2.27.0