x86/SVM: correct boot time cpu_data[] handling

start_svm() already runs after cpu_data[] was set up, so it shouldn't
modify it anymore (at least not directly). Constify the involved
pointers.

Furthermore LMSLE feature detection was broken by 566ddbe833 ("x86:
Fail CPU bringup cleanly if it cannot initialise HVM"), as Andrew
Cooper has pointed out: c couldn't possibly equal &boot_cpu_data
anymore. (But since it's unsafe migration-wise for some more time,
suppress the feature actually being enabled for us.)

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen/arch/x86/hvm/svm/asid.c

@@ -22,7 +22,7 @@
 #include <asm/amd.h>
 #include <asm/hvm/nestedhvm.h>
 
-void svm_asid_init(struct cpuinfo_x86 *c)
+void svm_asid_init(const struct cpuinfo_x86 *c)
 {
     int nasids = 0;
 

xen/arch/x86/hvm/svm/svm.c

@@ -1330,7 +1330,7 @@ static int svm_cpu_up_prepare(unsigned int cpu)
     return 0;
 }
 
-static void svm_init_erratum_383(struct cpuinfo_x86 *c)
+static void svm_init_erratum_383(const struct cpuinfo_x86 *c)
 {
     uint64_t msr_content;
 
@@ -1365,11 +1365,12 @@ static int svm_handle_osvw(struct vcpu *v, uint32_t msr, uint64_t *val, bool_t r
     return 0;
 }
 
-static int svm_cpu_up(void)
+static int _svm_cpu_up(bool bsp)
 {
     uint64_t msr_content;
-    int rc, cpu = smp_processor_id();
-    struct cpuinfo_x86 *c = &cpu_data[cpu];
+    int rc;
+    unsigned int cpu = smp_processor_id();
+    const struct cpuinfo_x86 *c = &cpu_data[cpu];
  
     /* Check whether SVM feature is disabled in BIOS */
     rdmsrl(MSR_K8_VM_CR, msr_content);
@@ -1402,7 +1403,7 @@ static int svm_cpu_up(void)
         rdmsrl(MSR_EFER, msr_content);
     if ( msr_content & EFER_LMSLE )
     {
-        if ( c == &boot_cpu_data )
+        if ( 0 && /* FIXME: Migration! */ bsp )
             cpu_has_lmsl = 1;
         wrmsrl(MSR_EFER, msr_content ^ EFER_LMSLE);
     }
@@ -1419,13 +1420,18 @@ static int svm_cpu_up(void)
     return 0;
 }
 
+static int svm_cpu_up(void)
+{
+    return _svm_cpu_up(false);
+}
+
 const struct hvm_function_table * __init start_svm(void)
 {
     bool_t printed = 0;
 
     svm_host_osvw_reset();
 
-    if ( svm_cpu_up() )
+    if ( _svm_cpu_up(true) )
     {
         printk("SVM: failed to initialise.\n");
         return NULL;

xen/include/asm-x86/hvm/svm/asid.h

@@ -22,7 +22,7 @@
 #include <asm/hvm/asid.h>
 #include <asm/processor.h>
 
-void svm_asid_init(struct cpuinfo_x86 *c);
+void svm_asid_init(const struct cpuinfo_x86 *c);
 
 static inline void svm_asid_g_invlpg(struct vcpu *v, unsigned long g_vaddr)
 {