+unsigned long lapic_read(unsigned long reg)
+{
+ return readl(LAPIC_DEFAULT_BASE + reg);
+}
+
+#define xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
+ sizeof(*(ptr))))
+
+struct __xchg_dummy { unsigned long a[100]; };
+#define __xg(x) ((struct __xchg_dummy *)(x))
+
+/*
+ * Note: no "lock" prefix even on SMP. xchg always implies lock anyway.
+ *
+ * Note 2: xchg has side effect, so that attribute volatile is necessary,
+ * but generally the primitive is invalid, *ptr is output argument.
+ */
+static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
+ int size)
+{
+ switch (size) {
+ case 1:
+ __asm__ __volatile__("xchgb %b0,%1"
+ : "=q" (x)
+ : "m" (*__xg(ptr)), "0" (x)
+ : "memory");
+ break;
+ case 2:
+ __asm__ __volatile__("xchgw %w0,%1"
+ : "=r" (x)
+ : "m" (*__xg(ptr)), "0" (x)
+ : "memory");
+ break;
+ case 4:
+ __asm__ __volatile__("xchgl %0,%1"
+ : "=r" (x)
+ : "m" (*__xg(ptr)), "0" (x)
+ : "memory");
+ break;
+ }
+
+ return x;
+}
+
+void lapic_write(unsigned long reg, unsigned long v)
+{
+ (void)xchg((volatile unsigned long *)(LAPIC_DEFAULT_BASE + reg), v);
+}
+
+void enable_lapic(void)
+{
+ msr_t msr;
+
+ msr = msr_read(MSR_IA32_APICBASE);
+ msr.hi &= 0xffffff00;
+ msr.lo |= MSR_IA32_APICBASE_ENABLE;
+ msr.lo &= ~MSR_IA32_APICBASE_BASE;
+ msr.lo |= LAPIC_DEFAULT_BASE;
+ msr_write(MSR_IA32_APICBASE, msr);
+}
+
+void disable_lapic(void)
+{
+ msr_t msr;
+
+ msr = msr_read(MSR_IA32_APICBASE);
+ msr.lo &= ~MSR_IA32_APICBASE_ENABLE;
+ msr_write(MSR_IA32_APICBASE, msr);
+}
+
+unsigned long lapicid(void)
+{
+ return lapic_read(LAPIC_ID) >> 24;
+}
+
+static void lapic_wait_icr_idle(void)
+{
+ do { } while (lapic_read(LAPIC_ICR) & LAPIC_ICR_BUSY);
+}
+
+int lapic_remote_read(int apicid, int reg, unsigned long *pvalue)
+{
+ int timeout;
+ unsigned long status;
+ int result;
+
+ lapic_wait_icr_idle();
+ lapic_write(LAPIC_ICR2, SET_LAPIC_DEST_FIELD(apicid));
+ lapic_write(LAPIC_ICR, LAPIC_DM_REMRD | (reg >> 4));
+
+ timeout = 0;
+ do {
+ status = lapic_read(LAPIC_ICR) & LAPIC_ICR_RR_MASK;
+ } while (status == LAPIC_ICR_RR_INPROG && timeout++ < 1000);
+
+ result = -1;
+ if (status == LAPIC_ICR_RR_VALID) {
+ *pvalue = lapic_read(LAPIC_RRR);
+ result = 0;
+ }
+
+ return result;
+}
+