On Wed, Nov 09, 2016 at 06:35:13PM -0600, Tom Lendacky wrote:

+/*
+ * AMD Secure Memory Encryption (SME) can reduce the size of the physical
+ * address space if it is enabled, even if memory encryption is not active.
+ * Adjust x86_phys_bits if SME is enabled.
+ */
+static void phys_bits_adjust(struct cpuinfo_x86 *c)
+{

Better call this function amd_sme_phys_bits_adjust(). This name makes it
clear at the call-site why it is there and what it does.

+	u32 eax, ebx, ecx, edx;
+	u64 msr;
+
+	if (c->x86_vendor != X86_VENDOR_AMD)
+		return;
+
+	if (c->extended_cpuid_level < 0x8000001f)
+		return;
+
+	/* Check for SME feature */
+	cpuid(0x8000001f, &eax, &ebx, &ecx, &edx);
+	if (!(eax & 0x01))
+		return;

Maybe add a comment here why you can't use cpu_has (yet).