arch/x86/smp: remove MONITOR/MWAIT loop for TXT AP bringup

This is no longer necessary, since AP loops on cpu_state and CPU
index is passed as argument.

In addition, move TXT JOIN structure to static data. There is no
guarantee that it would be consumed before it is overwritten on BSP
stack.

Signed-off-by: Krystian Hebel <[email protected]>

Author: krystian-hebel

xen/arch/x86/smpboot.c

@@ -320,28 +320,6 @@ void asmlinkage start_secondary(unsigned int cpu)
      * want to limit the things done here to the most necessary things.
      */
 
-    if ( ap_boot_method == AP_BOOT_TXT ) {
-        uint64_t misc_enable;
-        uint32_t my_apicid;
-        struct txt_sinit_mle_data *sinit_mle =
-              txt_sinit_mle_data_start(__va(read_txt_reg(TXTCR_HEAP_BASE)));
-
-        /* TXT released us with MONITOR disabled in IA32_MISC_ENABLE. */
-        rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable);
-        wrmsrl(MSR_IA32_MISC_ENABLE,
-               misc_enable | MSR_IA32_MISC_ENABLE_MONITOR_ENABLE);
-
-        /* get_apic_id() reads from x2APIC if it thinks it is enabled. */
-        x2apic_ap_setup();
-        my_apicid = get_apic_id();
-
-        while ( my_apicid != cpu_physical_id(cpu) ) {
-            asm volatile ("monitor; xor %0,%0; mwait"
-                          :: "a"(__va(sinit_mle->rlp_wakeup_addr)), "c"(0),
-                          "d"(0) : "memory");
-        }
-    }
-
     /* Critical region without IDT or TSS.  Any fault is deadly! */
 
     /* Wait until data set up by CPU_UP_PREPARE notifiers is ready. */
@@ -455,13 +433,16 @@ static int wake_aps_in_txt(void)
     struct txt_sinit_mle_data *sinit_mle =
               txt_sinit_mle_data_start(__va(read_txt_reg(TXTCR_HEAP_BASE)));
     uint32_t *wakeup_addr = __va(sinit_mle->rlp_wakeup_addr);
+    static uint32_t join[4] = {0};
+
+    /* Check if already started. */
+    if ( join[0] != 0 )
+        return -1;
 
-    uint32_t join[4] = {
-        trampoline_gdt[1],               /* GDT limit */
-        bootsym_phys(trampoline_gdt),    /* GDT base */
-        TXT_AP_BOOT_CS,                  /* CS selector, DS = CS+8 */
-        bootsym_phys(txt_ap_entry)       /* EIP */
-    };
+    join[0] = trampoline_gdt[1];             /* GDT limit */
+    join[1] = bootsym_phys(trampoline_gdt);  /* GDT base */
+    join[2] = TXT_AP_BOOT_CS;                /* CS selector, DS = CS+8 */
+    join[3] = bootsym_phys(txt_ap_entry);    /* EIP */
 
     write_txt_reg(TXTCR_MLE_JOIN, __pa(join));