static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
{
	int ret;
#ifdef CONFIG_X86_64
	unsigned int which;
	u64 base;
#endif

	ret = 0;

	switch (msr) {
#ifdef CONFIG_X86_64
	case MSR_FS_BASE:		which = SEGBASE_FS; goto set;
	case MSR_KERNEL_GS_BASE:	which = SEGBASE_GS_USER; goto set;
	case MSR_GS_BASE:		which = SEGBASE_GS_KERNEL; goto set;

	set:
		base = ((u64)high << 32) | low;
		if (HYPERVISOR_set_segment_base(which, base) != 0)
			ret = -EIO;
		break;
#endif

	case MSR_STAR:
	case MSR_CSTAR:
	case MSR_LSTAR:
	case MSR_SYSCALL_MASK:
	case MSR_IA32_SYSENTER_CS:
	case MSR_IA32_SYSENTER_ESP:
	case MSR_IA32_SYSENTER_EIP:
		/* Fast syscall setup is all done in hypercalls, so
		   these are all ignored.  Stub them out here to stop
		   Xen console noise. */
		break;

	default:
		if (!pmu_msr_write(msr, low, high, &ret))
			ret = native_write_msr_safe(msr, low, high);
	}

	return ret;
}
Unknown