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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 09/30] xen/x86: Store antifeatures inverted in a featureset
Awkwardly, some new feature bits mean "Feature $X no longer works".
Store these inverted in a featureset.
This permits safe zero-extending of a smaller featureset as part of a
comparison, and safe reasoning (subset?, superset?, compatible? etc.)
without specific knowldge of meaning of each bit.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
v2: Annotate inverted features using a magic comment and autogeneration.
---
xen/arch/x86/cpu/common.c | 1 +
xen/arch/x86/cpuid.c | 2 ++
xen/include/asm-x86/cpufeature.h | 2 +-
xen/include/asm-x86/cpuid.h | 1 +
xen/include/public/arch-x86/cpufeatureset.h | 18 +++++++++++++++++-
xen/tools/gen-cpuid.py | 15 ++++++++++++++-
6 files changed, 36 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 151dfe4..39c340b 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -343,6 +343,7 @@ void identify_cpu(struct cpuinfo_x86 *c)
*/
for (i = 0; i < FSCAPINTS; ++i) {
c->x86_capability[i] &= known_features[i];
+ c->x86_capability[i] ^= inverted_features[i];
}
for (i = 0 ; i < NCAPINTS ; ++i)
diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index fb3a6ac..30a3392 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -2,10 +2,12 @@
#include <asm/cpuid.h>
const uint32_t known_features[] = INIT_KNOWN_FEATURES;
+const uint32_t inverted_features[] = INIT_INVERTED_FEATURES;
static void __maybe_unused build_assertions(void)
{
BUILD_BUG_ON(ARRAY_SIZE(known_features) != FSCAPINTS);
+ BUILD_BUG_ON(ARRAY_SIZE(inverted_features) != FSCAPINTS);
}
/*
diff --git a/xen/include/asm-x86/cpufeature.h b/xen/include/asm-x86/cpufeature.h
index a984a81..f228fa2 100644
--- a/xen/include/asm-x86/cpufeature.h
+++ b/xen/include/asm-x86/cpufeature.h
@@ -65,7 +65,7 @@
#define cpu_has_smep boot_cpu_has(X86_FEATURE_SMEP)
#define cpu_has_smap boot_cpu_has(X86_FEATURE_SMAP)
-#define cpu_has_fpu_sel (!boot_cpu_has(X86_FEATURE_NO_FPU_SEL))
+#define cpu_has_fpu_sel boot_cpu_has(X86_FEATURE_FPU_SEL)
#define cpu_has_ffxsr ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) \
&& boot_cpu_has(X86_FEATURE_FFXSR))
diff --git a/xen/include/asm-x86/cpuid.h b/xen/include/asm-x86/cpuid.h
index 6cca5ea..341dbc1 100644
--- a/xen/include/asm-x86/cpuid.h
+++ b/xen/include/asm-x86/cpuid.h
@@ -9,6 +9,7 @@
#include <xen/types.h>
extern const uint32_t known_features[FSCAPINTS];
+extern const uint32_t inverted_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 02d695d..2748cfd 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -37,10 +37,26 @@
* contain any synthesied values. New words may be added to the end of
* featureset.
*
+ * "Anti" features have their representation inverted. This permits safe
+ * zero-extending of a smaller featureset as part of a comparison, and safe
+ * reasoning (subset?, superset?, compatible? etc.) without specific knowldge
+ * of meaning of each bit.
+ *
* All featureset words currently originate from leaves specified for the
* 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.
+ *
+ * Inverted: '!'
+ * This feature has its value in a featureset inverted, compared to how it
+ * is specified by vendor architecture manuals.
+ */
+
/* Intel-defined CPU features, CPUID level 0x00000001.edx, word 0 */
#define X86_FEATURE_FPU ( 0*32+ 0) /* Onboard FPU */
#define X86_FEATURE_VME ( 0*32+ 1) /* Virtual Mode Extensions */
@@ -158,7 +174,7 @@
#define X86_FEATURE_INVPCID ( 5*32+10) /* Invalidate Process Context
ID */
#define X86_FEATURE_RTM ( 5*32+11) /* Restricted Transactional
Memory */
#define X86_FEATURE_CMT ( 5*32+12) /* Cache Monitoring Technology
*/
-#define X86_FEATURE_NO_FPU_SEL ( 5*32+13) /* FPU CS/DS stored as zero */
+#define X86_FEATURE_FPU_SEL ( 5*32+13) /*! FPU CS/DS stored as zero */
#define X86_FEATURE_MPX ( 5*32+14) /* Memory Protection Extensions
*/
#define X86_FEATURE_CAT ( 5*32+15) /* Cache Allocation Technology
*/
#define X86_FEATURE_RDSEED ( 5*32+18) /* RDSEED instruction */
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 0843be6..9e0cc34 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_inverted = []
# State calculated
self.nr_entries = 0 # Number of words in a featureset
self.common = 0 # Common features between 1d and e1d
self.known = [] # All known features
+ self.inverted = [] # Features with inverted representations
def parse_definitions(state):
"""
@@ -29,7 +31,8 @@ def parse_definitions(state):
"""
feat_regex = re.compile(
r"^#define X86_FEATURE_([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,))
@@ -60,6 +64,11 @@ def parse_definitions(state):
# Construct a reverse mapping of value to name
state.names[val] = name
+ if len(attr):
+
+ if "!" in attr:
+ state.raw_inverted.append(val)
+
def featureset_to_uint32s(fs, nr):
""" Represent a featureset as a list of C-compatible uint32_t's """
@@ -106,6 +115,7 @@ def crunch_numbers(state):
state.names[e1d_base + (f % 32)] = "E1D_" + state.names[f]
state.common = featureset_to_uint32s(common_1d, 1)[0]
+ state.inverted = featureset_to_uint32s(state.raw_inverted, nr_entries)
def write_results(state):
@@ -125,9 +135,12 @@ def write_results(state):
#define INIT_COMMON_FEATURES %s
#define INIT_KNOWN_FEATURES { \\\n%s\n}
+
+#define INIT_INVERTED_FEATURES { \\\n%s\n}
""" % (state.nr_entries,
state.common,
format_uint32s(state.known, 4),
+ format_uint32s(state.inverted, 4),
))
state.output.write(
--
2.1.4
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