D6059.id15491.diff
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	Index: sys/amd64/amd64/initcpu.c
	===================================================================
	--- sys/amd64/amd64/initcpu.c
	+++ sys/amd64/amd64/initcpu.c
	@@ -58,6 +58,7 @@
	static void
	init_amd(void)
	{
	+ uint64_t msr;

	/*
	* Work around Erratum 721 for Family 10h and 12h processors.
	@@ -80,6 +81,20 @@
	wrmsr(0xc0011029, rdmsr(0xc0011029) \| 1);
	break;
	}
	+
	+ /*
	+ * BIOS may configure Family 10h processors to convert WC+ cache type
	+ * to CD. That can hurt performance of guest VMs using nested paging.
	+ * The relevant MSR bit is not documented in the BKDG,
	+ * the fix is borrowed from Linux.
	+ */
	+ if (CPUID_TO_FAMILY(cpu_id) == 0x10) {
	+ if ((cpu_feature2 & CPUID2_HV) == 0) {
	+ msr = rdmsr(0xc001102a);
	+ msr &= ~((uint64_t)1 << 24);
	+ wrmsr(0xc001102a, msr);
	+ }
	+ }
	}

	/*