AMD OSVW (OS Visible Workaround) for Xen

This path enables AMD OSVW (OS Visible Workaround) feature for
Xen. New AMD errata will have a OSVW id assigned in the future. OS is
supposed to check OSVW status MSR to find out whether CPU has a
specific erratum. Legacy errata are also supported in this patch:
traditional family/model/stepping approach will be used if OSVW
feature isn't applicable.  This patch is adapted from Hans Rosenfeld's
patch submitted to Linux kernel.

Signed-off-by: Wei Huang <wei.huang2@amd.com>
Signed-off-by: Hans Rosenfeld <hands.rosenfeld@amd.com>
Acked-by: Jan Beulich <jbeulich@novell.com>

xen/arch/x86/cpu/amd.c

@@ -7,12 +7,12 @@
 #include <asm/io.h>
 #include <asm/msr.h>
 #include <asm/processor.h>
+#include <asm/amd.h>
 #include <asm/hvm/support.h>
 #include <asm/setup.h> /* amd_init_cpu */
 #include <asm/acpi.h>
 
 #include "cpu.h"
-#include "amd.h"
 
 /*
  * Pre-canned values for overriding the CPUID features 
@@ -147,6 +147,54 @@ static void __devinit set_cpuidmask(const struct cpuinfo_x86 *c)
 	}
 }
 
+/*
+ * Check for the presence of an AMD erratum. Arguments are defined in amd.h 
+ * for each known erratum. Return 1 if erratum is found.
+ */
+int cpu_has_amd_erratum(const struct cpuinfo_x86 *cpu, int osvw, ...) 
+{
+	va_list ap;
+	u32 range;
+	u32 ms;
+	
+	if (cpu->x86_vendor != X86_VENDOR_AMD)
+		return 0;
+
+	va_start(ap, osvw);
+
+	if (osvw) {
+		u16 osvw_id = va_arg(ap, int);
+
+		if (cpu_has(cpu, X86_FEATURE_OSVW)) {
+			u64 osvw_len;
+			rdmsrl(MSR_AMD_OSVW_ID_LENGTH, osvw_len);
+
+			if (osvw_id < osvw_len) {
+				u64 osvw_bits;
+				rdmsrl(MSR_AMD_OSVW_STATUS + (osvw_id >> 6), 
+				       osvw_bits);
+
+				va_end(ap);
+				return (osvw_bits >> (osvw_id & 0x3f)) & 0x01;
+			}
+		}
+	}
+
+	/* OSVW unavailable or ID unknown, match family-model-stepping range */
+	ms = (cpu->x86_model << 8) | cpu->x86_mask;
+	while ((range = va_arg(ap, int))) {
+		if ((cpu->x86 == AMD_MODEL_RANGE_FAMILY(range)) &&
+		    (ms >= AMD_MODEL_RANGE_START(range)) &&
+		    (ms <= AMD_MODEL_RANGE_END(range))) {
+			va_end(ap);
+			return 1;
+		}
+	}
+
+	va_end(ap);
+	return 0;
+}
+
 /*
  * amd_flush_filter={on,off}. Forcibly Enable or disable the TLB flush
  * filter on AMD 64-bit processors.

xen/arch/x86/hvm/svm/asid.c

@@ -21,14 +21,14 @@
 #include <xen/lib.h>
 #include <xen/perfc.h>
 #include <asm/hvm/svm/asid.h>
+#include <asm/amd.h>
 
 void svm_asid_init(struct cpuinfo_x86 *c)
 {
     int nasids = 0;
 
     /* Check for erratum #170, and leave ASIDs disabled if it's present. */
-    if ( (c->x86 == 0x10) ||
-         ((c->x86 == 0xf) && (c->x86_model >= 0x68) && (c->x86_mask >= 1)) )
+    if ( !cpu_has_amd_erratum(c, AMD_ERRATUM_170) )
         nasids = cpuid_ebx(0x8000000A);
 
     hvm_asid_init(nasids);

xen/arch/x86/hvm/svm/svm.c

@@ -34,6 +34,7 @@
 #include <asm/regs.h>
 #include <asm/cpufeature.h>
 #include <asm/processor.h>
+#include <asm/amd.h>
 #include <asm/types.h>
 #include <asm/debugreg.h>
 #include <asm/msr.h>
@@ -846,8 +847,8 @@ static void svm_init_erratum_383(struct cpuinfo_x86 *c)
 {
     uint64_t msr_content;
 
-    /* only family 10h is affected */
-    if ( c->x86 != 0x10 )
+    /* check whether CPU is affected */
+    if ( !cpu_has_amd_erratum(c, AMD_ERRATUM_383) )
         return;
 
     /* use safe methods to be compatible with nested virtualization */

xen/include/asm-x86/amd.h

@@ -100,4 +100,39 @@
 	__bit(X86_FEATURE_SKINIT))
 #define AMD_EXTFEATURES_FAM11h_REV_B_EDX  AMD_EXTFEATURES_K8_REV_G_EDX
 
+/* AMD errata checking
+ *
+ * Errata are defined using the AMD_LEGACY_ERRATUM() or AMD_OSVW_ERRATUM()
+ * macros. The latter is intended for newer errata that have an OSVW id
+ * assigned, which it takes as first argument. Both take a variable number
+ * of family-specific model-stepping ranges created by AMD_MODEL_RANGE().
+ *
+ * Example 1:
+ * #define AMD_ERRATUM_319                                              \
+ *   AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x10, 0x2, 0x1, 0x4, 0x2),      \
+ *                      AMD_MODEL_RANGE(0x10, 0x8, 0x0, 0x8, 0x0),      \
+ *                      AMD_MODEL_RANGE(0x10, 0x9, 0x0, 0x9, 0x0))
+ * Example 2:
+ * #define AMD_ERRATUM_400                                              \
+ *   AMD_OSVW_ERRATUM(1, AMD_MODEL_RANGE(0xf, 0x41, 0x2, 0xff, 0xf),    \
+ *                       AMD_MODEL_RANGE(0x10, 0x2, 0x1, 0xff, 0xf))
+ *   
+ */
+
+#define AMD_LEGACY_ERRATUM(...)         0 /* legacy */, __VA_ARGS__, 0
+#define AMD_OSVW_ERRATUM(osvw_id, ...)  1 /* osvw */, osvw_id, __VA_ARGS__, 0
+#define AMD_MODEL_RANGE(f, m_start, s_start, m_end, s_end)              \
+    ((f << 24) | (m_start << 16) | (s_start << 12) | (m_end << 4) | (s_end))
+#define AMD_MODEL_RANGE_FAMILY(range)   (((range) >> 24) & 0xff)
+#define AMD_MODEL_RANGE_START(range)    (((range) >> 12) & 0xfff)
+#define AMD_MODEL_RANGE_END(range)      ((range) & 0xfff)
+
+#define AMD_ERRATUM_170                                                 \
+    AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x0f, 0x0, 0x0, 0x67, 0xf))
+
+#define AMD_ERRATUM_383                                                 \
+    AMD_OSVW_ERRATUM(3, AMD_MODEL_RANGE(0x10, 0x2, 0x1, 0xff, 0xf),	\
+		        AMD_MODEL_RANGE(0x12, 0x0, 0x0, 0x1, 0x0))
+
+int cpu_has_amd_erratum(const struct cpuinfo_x86 *, int, ...);
 #endif /* __AMD_H__ */

xen/include/asm-x86/msr-index.h

@@ -252,6 +252,10 @@
 #define MSR_AMD_PATCHLEVEL		0x0000008b
 #define MSR_AMD_PATCHLOADER		0xc0010020
 
+/* AMD OS Visible Workaround MSRs */
+#define MSR_AMD_OSVW_ID_LENGTH          0xc0010140
+#define MSR_AMD_OSVW_STATUS             0xc0010141
+
 /* K6 MSRs */
 #define MSR_K6_EFER			0xc0000080
 #define MSR_K6_STAR			0xc0000081