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-rw-r--r--arch/x86/kvm/reverse_cpuid.h187
1 files changed, 187 insertions, 0 deletions
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
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+++ b/arch/x86/kvm/reverse_cpuid.h
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+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef ARCH_X86_KVM_REVERSE_CPUID_H
+#define ARCH_X86_KVM_REVERSE_CPUID_H
+
+#include <uapi/asm/kvm.h>
+#include <asm/cpufeature.h>
+#include <asm/cpufeatures.h>
+
+/*
+ * Hardware-defined CPUID leafs that are scattered in the kernel, but need to
+ * be directly used by KVM. Note, these word values conflict with the kernel's
+ * "bug" caps, but KVM doesn't use those.
+ */
+enum kvm_only_cpuid_leafs {
+ CPUID_12_EAX = NCAPINTS,
+ NR_KVM_CPU_CAPS,
+
+ NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
+};
+
+#define KVM_X86_FEATURE(w, f) ((w)*32 + (f))
+
+/* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
+#define KVM_X86_FEATURE_SGX1 KVM_X86_FEATURE(CPUID_12_EAX, 0)
+#define KVM_X86_FEATURE_SGX2 KVM_X86_FEATURE(CPUID_12_EAX, 1)
+
+struct cpuid_reg {
+ u32 function;
+ u32 index;
+ int reg;
+};
+
+static const struct cpuid_reg reverse_cpuid[] = {
+ [CPUID_1_EDX] = { 1, 0, CPUID_EDX},
+ [CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
+ [CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX},
+ [CPUID_1_ECX] = { 1, 0, CPUID_ECX},
+ [CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX},
+ [CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX},
+ [CPUID_7_0_EBX] = { 7, 0, CPUID_EBX},
+ [CPUID_D_1_EAX] = { 0xd, 1, CPUID_EAX},
+ [CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX},
+ [CPUID_6_EAX] = { 6, 0, CPUID_EAX},
+ [CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX},
+ [CPUID_7_ECX] = { 7, 0, CPUID_ECX},
+ [CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
+ [CPUID_7_EDX] = { 7, 0, CPUID_EDX},
+ [CPUID_7_1_EAX] = { 7, 1, CPUID_EAX},
+ [CPUID_12_EAX] = {0x00000012, 0, CPUID_EAX},
+ [CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
+ [CPUID_8000_0021_EAX] = {0x80000021, 0, CPUID_EAX},
+};
+
+/*
+ * Reverse CPUID and its derivatives can only be used for hardware-defined
+ * feature words, i.e. words whose bits directly correspond to a CPUID leaf.
+ * Retrieving a feature bit or masking guest CPUID from a Linux-defined word
+ * is nonsensical as the bit number/mask is an arbitrary software-defined value
+ * and can't be used by KVM to query/control guest capabilities. And obviously
+ * the leaf being queried must have an entry in the lookup table.
+ */
+static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
+{
+ BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
+ BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
+ BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
+ BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
+ BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
+ BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
+}
+
+/*
+ * Translate feature bits that are scattered in the kernel's cpufeatures word
+ * into KVM feature words that align with hardware's definitions.
+ */
+static __always_inline u32 __feature_translate(int x86_feature)
+{
+ if (x86_feature == X86_FEATURE_SGX1)
+ return KVM_X86_FEATURE_SGX1;
+ else if (x86_feature == X86_FEATURE_SGX2)
+ return KVM_X86_FEATURE_SGX2;
+
+ return x86_feature;
+}
+
+static __always_inline u32 __feature_leaf(int x86_feature)
+{
+ return __feature_translate(x86_feature) / 32;
+}
+
+/*
+ * Retrieve the bit mask from an X86_FEATURE_* definition. Features contain
+ * the hardware defined bit number (stored in bits 4:0) and a software defined
+ * "word" (stored in bits 31:5). The word is used to index into arrays of
+ * bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
+ */
+static __always_inline u32 __feature_bit(int x86_feature)
+{
+ x86_feature = __feature_translate(x86_feature);
+
+ reverse_cpuid_check(x86_feature / 32);
+ return 1 << (x86_feature & 31);
+}
+
+#define feature_bit(name) __feature_bit(X86_FEATURE_##name)
+
+static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature)
+{
+ unsigned int x86_leaf = __feature_leaf(x86_feature);
+
+ reverse_cpuid_check(x86_leaf);
+ return reverse_cpuid[x86_leaf];
+}
+
+static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
+ u32 reg)
+{
+ switch (reg) {
+ case CPUID_EAX:
+ return &entry->eax;
+ case CPUID_EBX:
+ return &entry->ebx;
+ case CPUID_ECX:
+ return &entry->ecx;
+ case CPUID_EDX:
+ return &entry->edx;
+ default:
+ BUILD_BUG();
+ return NULL;
+ }
+}
+
+static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
+ unsigned int x86_feature)
+{
+ const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
+
+ return __cpuid_entry_get_reg(entry, cpuid.reg);
+}
+
+static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
+ unsigned int x86_feature)
+{
+ u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
+
+ return *reg & __feature_bit(x86_feature);
+}
+
+static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
+ unsigned int x86_feature)
+{
+ return cpuid_entry_get(entry, x86_feature);
+}
+
+static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry,
+ unsigned int x86_feature)
+{
+ u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
+
+ *reg &= ~__feature_bit(x86_feature);
+}
+
+static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry,
+ unsigned int x86_feature)
+{
+ u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
+
+ *reg |= __feature_bit(x86_feature);
+}
+
+static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
+ unsigned int x86_feature,
+ bool set)
+{
+ u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
+
+ /*
+ * Open coded instead of using cpuid_entry_{clear,set}() to coerce the
+ * compiler into using CMOV instead of Jcc when possible.
+ */
+ if (set)
+ *reg |= __feature_bit(x86_feature);
+ else
+ *reg &= ~__feature_bit(x86_feature);
+}
+
+#endif /* ARCH_X86_KVM_REVERSE_CPUID_H */