[PATCH v4 05/26] xen/x86: Annotate special features

[Andrew Cooper <andrew.cooper3@citrix.com>]

Some bits in a featureset are not simple a indication of new functionality,
and require special handling.

APIC, OSXSAVE and OSPKE are fast-forwards of other pieces of state;
IA32_APIC_BASE.EN, CR4.OSXSAVE and CR4.OSPKE.  Xen will take care of filling
these appropriately at runtime.

FDP_EXCP_ONLY and NO_FPU_SEL are bits indicating reduced functionality in the
x87 pipeline.  The effects of these cannot be hidden from the guest, so the
host values will always be provided.

HTT, X2APIC and CMP_LEGACY indicate how to interpret other cpuid leaves.  In
most cases, the toolstack value will be used (with the expectation that these
flags will match the other provided topology information).  However with cpuid
masking, the host values are presented as masking cannot influence what the
guest sees in the dependent leaves.

HYPERVISOR is unconditionally set in the PV ABI, but follows the toolstack
setting for HVM guests.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
v3:
 * Essentially new.  Replaces "Store antifeatures inverted in a featureset"
v4:
 * Include X2APIC and HYPERVISOR as special bits.
---
 xen/arch/x86/cpuid.c                        |  2 ++
 xen/include/asm-x86/cpuid.h                 |  1 +
 xen/include/public/arch-x86/cpufeatureset.h | 30 ++++++++++++++++++++---------
 xen/tools/gen-cpuid.py                      | 17 +++++++++++++++-
 4 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index 05cd646..77e008a 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -3,10 +3,12 @@
 #include <asm/cpuid.h>
 
 const uint32_t known_features[] = INIT_KNOWN_FEATURES;
+const uint32_t special_features[] = INIT_SPECIAL_FEATURES;
 
 static void __init __maybe_unused build_assertions(void)
 {
     BUILD_BUG_ON(ARRAY_SIZE(known_features) != FSCAPINTS);
+    BUILD_BUG_ON(ARRAY_SIZE(special_features) != FSCAPINTS);
 }
 
 /*
diff --git a/xen/include/asm-x86/cpuid.h b/xen/include/asm-x86/cpuid.h
index b72d88f..0ecf357 100644
--- a/xen/include/asm-x86/cpuid.h
+++ b/xen/include/asm-x86/cpuid.h
@@ -10,6 +10,7 @@
 #include <xen/types.h>
 
 extern const uint32_t known_features[FSCAPINTS];
+extern const uint32_t special_features[FSCAPINTS];
 
 #endif /* __ASSEMBLY__ */
 #endif /* !__X86_CPUID_H__ */
diff --git a/xen/include/public/arch-x86/cpufeatureset.h b/xen/include/public/arch-x86/cpufeatureset.h
index 5da37eb..8308972 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -71,6 +71,18 @@ enum {
  * CPUID instruction, but this is not preclude other sources of information.
  */
 
+/*
+ * Attribute syntax:
+ *
+ * Attributes for a particular feature are provided as characters before the
+ * first space in the comment immediately following the feature value.
+ *
+ * Special: '!'
+ *   This bit has special properties and is not a straight indication of a
+ *   piece of new functionality.  Xen will handle these differently,
+ *   and may override toolstack settings completely.
+ */
+
 /* Intel-defined CPU features, CPUID level 0x00000001.edx, word 0 */
 XEN_CPUFEATURE(FPU,           0*32+ 0) /*   Onboard FPU */
 XEN_CPUFEATURE(VME,           0*32+ 1) /*   Virtual Mode Extensions */
@@ -81,7 +93,7 @@ XEN_CPUFEATURE(MSR,           0*32+ 5) /*   Model-Specific Registers, RDMSR, WRM
 XEN_CPUFEATURE(PAE,           0*32+ 6) /*   Physical Address Extensions */
 XEN_CPUFEATURE(MCE,           0*32+ 7) /*   Machine Check Architecture */
 XEN_CPUFEATURE(CX8,           0*32+ 8) /*   CMPXCHG8 instruction */
-XEN_CPUFEATURE(APIC,          0*32+ 9) /*   Onboard APIC */
+XEN_CPUFEATURE(APIC,          0*32+ 9) /*!  Onboard APIC */
 XEN_CPUFEATURE(SEP,           0*32+11) /*   SYSENTER/SYSEXIT */
 XEN_CPUFEATURE(MTRR,          0*32+12) /*   Memory Type Range Registers */
 XEN_CPUFEATURE(PGE,           0*32+13) /*   Page Global Enable */
@@ -96,7 +108,7 @@ XEN_CPUFEATURE(MMX,           0*32+23) /*   Multimedia Extensions */
 XEN_CPUFEATURE(FXSR,          0*32+24) /*   FXSAVE and FXRSTOR instructions */
 XEN_CPUFEATURE(SSE,           0*32+25) /*   Streaming SIMD Extensions */
 XEN_CPUFEATURE(SSE2,          0*32+26) /*   Streaming SIMD Extensions-2 */
-XEN_CPUFEATURE(HTT,           0*32+28) /*   Hyper-Threading Technology */
+XEN_CPUFEATURE(HTT,           0*32+28) /*!  Hyper-Threading Technology */
 XEN_CPUFEATURE(TM1,           0*32+29) /*   Thermal Monitor 1 */
 XEN_CPUFEATURE(PBE,           0*32+31) /*   Pending Break Enable */
 
@@ -119,17 +131,17 @@ XEN_CPUFEATURE(PCID,          1*32+17) /*   Process Context ID */
 XEN_CPUFEATURE(DCA,           1*32+18) /*   Direct Cache Access */
 XEN_CPUFEATURE(SSE4_1,        1*32+19) /*   Streaming SIMD Extensions 4.1 */
 XEN_CPUFEATURE(SSE4_2,        1*32+20) /*   Streaming SIMD Extensions 4.2 */
-XEN_CPUFEATURE(X2APIC,        1*32+21) /*   Extended xAPIC */
+XEN_CPUFEATURE(X2APIC,        1*32+21) /*!  Extended xAPIC */
 XEN_CPUFEATURE(MOVBE,         1*32+22) /*   movbe instruction */
 XEN_CPUFEATURE(POPCNT,        1*32+23) /*   POPCNT instruction */
 XEN_CPUFEATURE(TSC_DEADLINE,  1*32+24) /*   TSC Deadline Timer */
 XEN_CPUFEATURE(AESNI,         1*32+25) /*   AES instructions */
 XEN_CPUFEATURE(XSAVE,         1*32+26) /*   XSAVE/XRSTOR/XSETBV/XGETBV */
-XEN_CPUFEATURE(OSXSAVE,       1*32+27) /*   OSXSAVE */
+XEN_CPUFEATURE(OSXSAVE,       1*32+27) /*!  OSXSAVE */
 XEN_CPUFEATURE(AVX,           1*32+28) /*   Advanced Vector Extensions */
 XEN_CPUFEATURE(F16C,          1*32+29) /*   Half-precision convert instruction */
 XEN_CPUFEATURE(RDRAND,        1*32+30) /*   Digital Random Number Generator */
-XEN_CPUFEATURE(HYPERVISOR,    1*32+31) /*   Running under some hypervisor */
+XEN_CPUFEATURE(HYPERVISOR,    1*32+31) /*!  Running under some hypervisor */
 
 /* AMD-defined CPU features, CPUID level 0x80000001.edx, word 2 */
 XEN_CPUFEATURE(SYSCALL,       2*32+11) /*   SYSCALL/SYSRET */
@@ -144,7 +156,7 @@ XEN_CPUFEATURE(3DNOW,         2*32+31) /*   3DNow! */
 
 /* AMD-defined CPU features, CPUID level 0x80000001.ecx, word 3 */
 XEN_CPUFEATURE(LAHF_LM,       3*32+ 0) /*   LAHF/SAHF in long mode */
-XEN_CPUFEATURE(CMP_LEGACY,    3*32+ 1) /*   If yes HyperThreading not valid */
+XEN_CPUFEATURE(CMP_LEGACY,    3*32+ 1) /*!  If yes HyperThreading not valid */
 XEN_CPUFEATURE(SVM,           3*32+ 2) /*   Secure virtual machine */
 XEN_CPUFEATURE(EXTAPIC,       3*32+ 3) /*   Extended APIC space */
 XEN_CPUFEATURE(CR8_LEGACY,    3*32+ 4) /*   CR8 in 32-bit mode */
@@ -177,14 +189,14 @@ XEN_CPUFEATURE(TSC_ADJUST,    5*32+ 1) /*   TSC_ADJUST MSR available */
 XEN_CPUFEATURE(BMI1,          5*32+ 3) /*   1st bit manipulation extensions */
 XEN_CPUFEATURE(HLE,           5*32+ 4) /*   Hardware Lock Elision */
 XEN_CPUFEATURE(AVX2,          5*32+ 5) /*   AVX2 instructions */
-XEN_CPUFEATURE(FDP_EXCP_ONLY, 5*32+ 6) /*   x87 FDP only updated on exception. */
+XEN_CPUFEATURE(FDP_EXCP_ONLY, 5*32+ 6) /*!  x87 FDP only updated on exception. */
 XEN_CPUFEATURE(SMEP,          5*32+ 7) /*   Supervisor Mode Execution Protection */
 XEN_CPUFEATURE(BMI2,          5*32+ 8) /*   2nd bit manipulation extensions */
 XEN_CPUFEATURE(ERMS,          5*32+ 9) /*   Enhanced REP MOVSB/STOSB */
 XEN_CPUFEATURE(INVPCID,       5*32+10) /*   Invalidate Process Context ID */
 XEN_CPUFEATURE(RTM,           5*32+11) /*   Restricted Transactional Memory */
 XEN_CPUFEATURE(PQM,           5*32+12) /*   Platform QoS Monitoring */
-XEN_CPUFEATURE(NO_FPU_SEL,    5*32+13) /*   FPU CS/DS stored as zero */
+XEN_CPUFEATURE(NO_FPU_SEL,    5*32+13) /*!  FPU CS/DS stored as zero */
 XEN_CPUFEATURE(MPX,           5*32+14) /*   Memory Protection Extensions */
 XEN_CPUFEATURE(PQE,           5*32+15) /*   Platform QoS Enforcement */
 XEN_CPUFEATURE(RDSEED,        5*32+18) /*   RDSEED instruction */
@@ -198,7 +210,7 @@ XEN_CPUFEATURE(SHA,           5*32+29) /*   SHA1 & SHA256 instructions */
 /* Intel-defined CPU features, CPUID level 0x00000007:0.ecx, word 6 */
 XEN_CPUFEATURE(PREFETCHWT1,   6*32+ 0) /*   PREFETCHWT1 instruction */
 XEN_CPUFEATURE(PKU,           6*32+ 3) /*   Protection Keys for Userspace */
-XEN_CPUFEATURE(OSPKE,         6*32+ 4) /*   OS Protection Keys Enable */
+XEN_CPUFEATURE(OSPKE,         6*32+ 4) /*!  OS Protection Keys Enable */
 
 /* AMD-defined CPU features, CPUID level 0x80000007.edx, word 7 */
 XEN_CPUFEATURE(ITSC,          7*32+ 8) /*   Invariant TSC */
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 44b4c98..5076fb9 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -16,11 +16,13 @@ class State(object):
 
         # State parsed from input
         self.names = {} # Name => value mapping
+        self.raw_special = set()
 
         # State calculated
         self.nr_entries = 0 # Number of words in a featureset
         self.common_1d = 0 # Common features between 1d and e1d
         self.known = [] # All known features
+        self.special = [] # Features with special semantics
 
 def parse_definitions(state):
     """
@@ -29,7 +31,8 @@ def parse_definitions(state):
     """
     feat_regex = re.compile(
         r"^XEN_CPUFEATURE\(([A-Z0-9_]+),"
-        "\s+([\s\d]+\*[\s\d]+\+[\s\d]+)\).*$")
+        "\s+([\s\d]+\*[\s\d]+\+[\s\d]+)\)"
+        "\s+/\*([!]*) .*$")
 
     this = sys.modules[__name__]
 
@@ -45,6 +48,7 @@ def parse_definitions(state):
 
         name = res.groups()[0]
         val = eval(res.groups()[1]) # Regex confines this to a very simple expression
+        attr = res.groups()[2]
 
         if hasattr(this, name):
             raise Fail("Duplicate symbol %s" % (name,))
@@ -64,6 +68,13 @@ def parse_definitions(state):
         # Construct a reverse mapping of value to name
         state.names[val] = name
 
+        for a in attr:
+
+            if a == "!":
+                state.raw_special.add(val)
+            else:
+                raise Fail("Unrecognised attribute '%s' for %s" % (a, name))
+
     if len(state.names) == 0:
         raise Fail("No features found")
 
@@ -112,6 +123,7 @@ def crunch_numbers(state):
         state.names[e1d_base + (f % 32)] = "E1D_" + state.names[f]
 
     state.common_1d = featureset_to_uint32s(common_1d, 1)[0]
+    state.special = featureset_to_uint32s(state.raw_special, nr_entries)
 
 
 def write_results(state):
@@ -131,9 +143,12 @@ def write_results(state):
 #define CPUID_COMMON_1D_FEATURES %s
 
 #define INIT_KNOWN_FEATURES { \\\n%s\n}
+
+#define INIT_SPECIAL_FEATURES { \\\n%s\n}
 """ % (state.nr_entries,
        state.common_1d,
        format_uint32s(state.known, 4),
+       format_uint32s(state.special, 4),
        ))
 
     state.output.write(
-- 
2.1.4


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