x86: KVM: Advertise AMX-FP16 CPUID to user space

mainline inclusion
from mainline-v6.2-rc1
commit af2872f6
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I8GYV5
CVE: N/A
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=af2872f6225476566bcbbd523a74dcaba29e159e



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Intel-SIG: commit af2872f6 ("x86: KVM: Advertise AMX-FP16 CPUID to user space")

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x86: KVM: Advertise AMX-FP16 CPUID to user space

Latest Intel platform Granite Rapids has introduced a new instruction -
AMX-FP16, which performs dot-products of two FP16 tiles and accumulates
the results into a packed single precision tile. AMX-FP16 adds FP16
capability and also allows a FP16 GPU trained model to run faster
without loss of accuracy or added SW overhead.

The bit definition:
CPUID.(EAX=7,ECX=1):EAX[bit 21]

AMX-FP16 is on an expected-dense CPUID leaf and some other bits on this
leaf have kernel usages. Given that, define this feature bit like
X86_FEATURE_<name> in kernel. Considering AMX-FP16 itself has no truly
kernel usages and /proc/cpuinfo has too much unreadable flags, hide this
one in /proc/cpuinfo.

Advertise AMX-FP16 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: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Jiaxi Chen <jiaxi.chen@linux.intel.com>
Acked-by: Borislav Petkov <bp@suse.de>
Message-Id: <20221125125845.1182922-5-jiaxi.chen@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Quanxian Wang <quanxian.wang@intel.com>