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AVX-NE-CONVERT is a new set of instructions which can convert low precision floating point like BF16/FP16 to high precision floating point FP32, and can also convert FP32 elements to BF16. This instruction allows the platform to have improved AI capabilities and better compatibility. The bit definition: CPUID.(EAX=7,ECX=1):EDX[bit 5] AVX-NE-CONVERT is on a KVM-only subleaf. Plus an x86_FEATURE definition for this feature bit to direct it to the KVM entry. Advertise AVX-NE-CONVERT to KVM userspace. This is safe because there are no new VMX controls or additional host enabling required for guests to use this feature. Signed-off-by: Jiaxi Chen <jiaxi.chen@linux.intel.com> Message-Id: <20221125125845.1182922-8-jiaxi.chen@linux.intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
205 lines
6.3 KiB
C
205 lines
6.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef ARCH_X86_KVM_REVERSE_CPUID_H
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#define ARCH_X86_KVM_REVERSE_CPUID_H
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#include <uapi/asm/kvm.h>
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#include <asm/cpufeature.h>
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#include <asm/cpufeatures.h>
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/*
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* Hardware-defined CPUID leafs that are either scattered by the kernel or are
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* unknown to the kernel, but need to be directly used by KVM. Note, these
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* word values conflict with the kernel's "bug" caps, but KVM doesn't use those.
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*/
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enum kvm_only_cpuid_leafs {
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CPUID_12_EAX = NCAPINTS,
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CPUID_7_1_EDX,
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NR_KVM_CPU_CAPS,
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NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
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};
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/*
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* Define a KVM-only feature flag.
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*
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* For features that are scattered by cpufeatures.h, __feature_translate() also
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* needs to be updated to translate the kernel-defined feature into the
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* KVM-defined feature.
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*
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* For features that are 100% KVM-only, i.e. not defined by cpufeatures.h,
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* forego the intermediate KVM_X86_FEATURE and directly define X86_FEATURE_* so
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* that X86_FEATURE_* can be used in KVM. No __feature_translate() handling is
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* needed in this case.
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*/
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#define KVM_X86_FEATURE(w, f) ((w)*32 + (f))
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/* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
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#define KVM_X86_FEATURE_SGX1 KVM_X86_FEATURE(CPUID_12_EAX, 0)
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#define KVM_X86_FEATURE_SGX2 KVM_X86_FEATURE(CPUID_12_EAX, 1)
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/* Intel-defined sub-features, CPUID level 0x00000007:1 (EDX) */
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#define X86_FEATURE_AVX_VNNI_INT8 KVM_X86_FEATURE(CPUID_7_1_EDX, 4)
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#define X86_FEATURE_AVX_NE_CONVERT KVM_X86_FEATURE(CPUID_7_1_EDX, 5)
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struct cpuid_reg {
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u32 function;
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u32 index;
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int reg;
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};
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static const struct cpuid_reg reverse_cpuid[] = {
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[CPUID_1_EDX] = { 1, 0, CPUID_EDX},
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[CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
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[CPUID_8086_0001_EDX] = {0x80860001, 0, CPUID_EDX},
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[CPUID_1_ECX] = { 1, 0, CPUID_ECX},
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[CPUID_C000_0001_EDX] = {0xc0000001, 0, CPUID_EDX},
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[CPUID_8000_0001_ECX] = {0x80000001, 0, CPUID_ECX},
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[CPUID_7_0_EBX] = { 7, 0, CPUID_EBX},
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[CPUID_D_1_EAX] = { 0xd, 1, CPUID_EAX},
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[CPUID_8000_0008_EBX] = {0x80000008, 0, CPUID_EBX},
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[CPUID_6_EAX] = { 6, 0, CPUID_EAX},
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[CPUID_8000_000A_EDX] = {0x8000000a, 0, CPUID_EDX},
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[CPUID_7_ECX] = { 7, 0, CPUID_ECX},
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[CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
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[CPUID_7_EDX] = { 7, 0, CPUID_EDX},
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[CPUID_7_1_EAX] = { 7, 1, CPUID_EAX},
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[CPUID_12_EAX] = {0x00000012, 0, CPUID_EAX},
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[CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
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[CPUID_7_1_EDX] = { 7, 1, CPUID_EDX},
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};
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/*
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* Reverse CPUID and its derivatives can only be used for hardware-defined
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* feature words, i.e. words whose bits directly correspond to a CPUID leaf.
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* Retrieving a feature bit or masking guest CPUID from a Linux-defined word
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* is nonsensical as the bit number/mask is an arbitrary software-defined value
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* and can't be used by KVM to query/control guest capabilities. And obviously
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* the leaf being queried must have an entry in the lookup table.
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*/
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static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
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{
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BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
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BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
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BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
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BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
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BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
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BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
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}
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/*
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* Translate feature bits that are scattered in the kernel's cpufeatures word
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* into KVM feature words that align with hardware's definitions.
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*/
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static __always_inline u32 __feature_translate(int x86_feature)
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{
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if (x86_feature == X86_FEATURE_SGX1)
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return KVM_X86_FEATURE_SGX1;
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else if (x86_feature == X86_FEATURE_SGX2)
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return KVM_X86_FEATURE_SGX2;
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return x86_feature;
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}
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static __always_inline u32 __feature_leaf(int x86_feature)
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{
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return __feature_translate(x86_feature) / 32;
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}
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/*
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* Retrieve the bit mask from an X86_FEATURE_* definition. Features contain
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* the hardware defined bit number (stored in bits 4:0) and a software defined
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* "word" (stored in bits 31:5). The word is used to index into arrays of
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* bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
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*/
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static __always_inline u32 __feature_bit(int x86_feature)
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{
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x86_feature = __feature_translate(x86_feature);
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reverse_cpuid_check(x86_feature / 32);
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return 1 << (x86_feature & 31);
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}
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#define feature_bit(name) __feature_bit(X86_FEATURE_##name)
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static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_feature)
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{
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unsigned int x86_leaf = __feature_leaf(x86_feature);
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reverse_cpuid_check(x86_leaf);
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return reverse_cpuid[x86_leaf];
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}
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static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
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u32 reg)
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{
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switch (reg) {
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case CPUID_EAX:
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return &entry->eax;
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case CPUID_EBX:
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return &entry->ebx;
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case CPUID_ECX:
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return &entry->ecx;
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case CPUID_EDX:
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return &entry->edx;
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default:
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BUILD_BUG();
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return NULL;
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}
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}
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static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
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unsigned int x86_feature)
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{
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const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
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return __cpuid_entry_get_reg(entry, cpuid.reg);
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}
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static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
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unsigned int x86_feature)
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{
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u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
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return *reg & __feature_bit(x86_feature);
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}
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static __always_inline bool cpuid_entry_has(struct kvm_cpuid_entry2 *entry,
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unsigned int x86_feature)
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{
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return cpuid_entry_get(entry, x86_feature);
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}
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static __always_inline void cpuid_entry_clear(struct kvm_cpuid_entry2 *entry,
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unsigned int x86_feature)
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{
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u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
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*reg &= ~__feature_bit(x86_feature);
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}
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static __always_inline void cpuid_entry_set(struct kvm_cpuid_entry2 *entry,
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unsigned int x86_feature)
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{
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u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
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*reg |= __feature_bit(x86_feature);
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}
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static __always_inline void cpuid_entry_change(struct kvm_cpuid_entry2 *entry,
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unsigned int x86_feature,
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bool set)
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{
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u32 *reg = cpuid_entry_get_reg(entry, x86_feature);
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/*
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* Open coded instead of using cpuid_entry_{clear,set}() to coerce the
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* compiler into using CMOV instead of Jcc when possible.
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*/
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if (set)
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*reg |= __feature_bit(x86_feature);
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else
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*reg &= ~__feature_bit(x86_feature);
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}
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#endif /* ARCH_X86_KVM_REVERSE_CPUID_H */
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