Drop the explicit @func param from ->set_supported_cpuid() and instead
pull the CPUID function from the relevant entry.  This sets the stage
for hardening guest CPUID updates in future patches, e.g. allows adding
run-time assertions that the CPUID feature being changed is actually
a bit in the referenced CPUID entry.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Clear the output regs for the main CPUID 0x14 leaf (index=0) if Intel PT
isn't exposed to the guest.  Leaf 0x14 enumerates Intel PT capabilities
and should return zeroes if PT is not supported.  Incorrectly reporting
PT capabilities is essentially a cosmetic error, i.e. doesn't negatively
affect any known userspace/kernel, as the existence of PT itself is
correctly enumerated via CPUID 0x7.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Expose kvm_mpx_supported() as a static inline so that it can be inlined
in kvm_intel.ko.

No functional change intended.
Reviewed-by: NXiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Query supported_xcr0 when checking for MPX support instead of invoking
->mpx_supported() and drop ->mpx_supported() as kvm_mpx_supported() was
its last user.  Rename vmx_mpx_supported() to cpu_has_vmx_mpx() to
better align with VMX/VMCS nomenclature.

Modify VMX's adjustment of xcr0 to call cpus_has_vmx_mpx() (renamed from
vmx_mpx_supported()) directly to avoid reading supported_xcr0 before
it's fully configured.

No functional change intended.
Reviewed-by: NXiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
[Test that *all* bits are set. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add a new global variable, supported_xcr0, to track which xcr0 bits can
be exposed to the guest instead of calculating the mask on every call.
The supported bits are constant for a given instance of KVM.

This paves the way toward eliminating the ->mpx_supported() call in
kvm_mpx_supported(), e.g. eliminates multiple retpolines in VMX's nested
VM-Enter path, and eventually toward eliminating ->mpx_supported()
altogether.

No functional change intended.
Reviewed-by: NXiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Use __do_cpuid_func()'s common loop iterator, "i", when enumerating the
sub-leafs for CPUID 0xD now that the CPUID 0xD loop doesn't need to
manual maintain separate counts for the entries index and CPUID index.

No functional changed intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Drop a "nent >= maxnent" check in kvm_get_cpuid() that's fully redundant
now that kvm_get_cpuid() isn't indexing the array to pass an entry to
do_cpuid_func().
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add a struct to hold the array of CPUID entries and its associated
metadata when handling KVM_GET_SUPPORTED_CPUID.  Lookup and provide
the correct entry in do_host_cpuid(), which eliminates the majority of
array indexing shenanigans, e.g. entries[i -1], and generally makes the
code more readable.  The last array indexing holdout is kvm_get_cpuid(),
which can't really be avoided without throwing the baby out with the
bathwater.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Refactoring the sub-leaf handling for CPUID 0x4/0x8000001d to eliminate
a one-off variable and its associated brackets.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Declare "i" and "max_idx" at the top of __do_cpuid_func() to consolidate
a handful of declarations in various case statements.

More importantly, establish the pattern of using max_idx instead of e.g.
entry->eax as the loop terminator in preparation for refactoring how
entry is handled in __do_cpuid_func().

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move the nent vs. maxnent check and nent increment into do_host_cpuid()
to consolidate what is now identical code.  To signal success vs.
failure, return the entry and NULL respectively.  A future patch will
build on this to also move the entry retrieval into do_host_cpuid().

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Drop redundant checks when "emulating" SSBD feature across vendors,
i.e. advertising the AMD variant when running on an Intel CPU and vice
versa.  Both SPEC_CTRL_SSBD and AMD_SSBD are already defined in the
leaf-specific feature masks and are *not* forcefully set by the kernel,
i.e. will already be set in the entry when supported by the host.

Functionally, this changes nothing, but the redundant check is
confusing, especially when considering future patches that will further
differentiate between "real" and "emulated" feature bits.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Drop the index param from do_cpuid_7_mask() and instead switch on the
entry's index, which is guaranteed to be set by do_host_cpuid().

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Refactor the sub-leaf loop for CPUID 0x7 to move the main leaf out of
said loop.  The emitted code savings is basically a mirage, as the
handling of the main leaf can easily be split to its own helper to avoid
code bloat.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Increment the number of CPUID entries immediately after do_host_cpuid()
in preparation for moving the logic into do_host_cpuid().  Handle the
rare/impossible case of encountering a bogus sub-leaf by decrementing
the number entries on failure.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

WARN if the save state size for a valid XCR0-managed sub-leaf is zero,
which would indicate a KVM or CPU bug.  Add a comment to explain why KVM
WARNs so the reader doesn't have to tease out the relevant bits from
Intel's SDM and KVM's XCR0/XSS code.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Now that sub-leaf 1 is handled separately, verify the next sub-leaf is
needed before rejecting KVM_GET_SUPPORTED_CPUID due to an insufficiently
sized userspace array.

Note, although this is technically a bug, it's not visible to userspace
as KVM_GET_SUPPORTED_CPUID is guaranteed to fail on KVM_CPUID_SIGNATURE,
which is hardcoded to be added after leaf 0xD.  The real motivation for
the change is to tightly couple the nent/maxnent and do_host_cpuid()
sequences in preparation for future cleanup.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Mov the sub-leaf 1 handling for CPUID 0xD out of the index>0 loop so
that the loop only handles index>2.  Sub-leafs 2+ have identical
semantics, whereas sub-leaf 1 is effectively a feature sub-leaf.

Moving sub-leaf 1 out of the loop does duplicate a bit of code, but
the nent/maxnent code will be consolidated in a future patch, and
duplicating the clear of ECX/EDX is arguably a good thing as the reasons
for clearing said registers are completely different.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Verify that the next sub-leaf of CPUID 0x4 (or 0x8000001d) is valid
before rejecting the entire KVM_GET_SUPPORTED_CPUID due to insufficent
space in the userspace array.

Note, although this is technically a bug, it's not visible to userspace
as KVM_GET_SUPPORTED_CPUID is guaranteed to fail on KVM_CPUID_SIGNATURE,
which is hardcoded to be added after the affected leafs.  The real
motivation for the change is to tightly couple the nent/maxnent and
do_host_cpuid() sequences in preparation for future cleanup.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Clean up the error handling in kvm_dev_ioctl_get_cpuid(), which has
gotten a bit crusty as the function has evolved over the years.

Opportunistically hoist the static @funcs declaration to the top of the
function to make it more obvious that it's a "static const".

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Refactor the handling of the Centaur-only CPUID leaf to detect the leaf
via a runtime query instead of adding a one-off callback in the static
array.  When the callback was introduced, there were additional fields
in the array's structs, and more importantly, retpoline wasn't a thing.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move the guts of kvm_dev_ioctl_get_cpuid()'s CPUID func loop to a
separate helper to improve code readability and pave the way for future
cleanup.

No functional change intended.
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Fix a long-standing bug that causes KVM to return 0 instead of -E2BIG
when userspace's array is insufficiently sized.

This technically breaks backwards compatibility, e.g. a userspace with a
hardcoded cpuid->nent could theoretically be broken as it would see an
error instead of success if cpuid->nent is less than the number of
entries required to fully enumerate the host CPU.  But, the lowest known
cpuid->nent hardcoded by a VMM is 100 (lkvm and selftests), and the
limit for current processors on Intel and AMD is well under a 100.  E.g.
Intel's Icelake server with all the bells and whistles tops out at ~60
entries (variable due to SGX sub-leafs), and AMD's CPUID documentation
allows for less than 50.  CPUID 0xD sub-leaves on current kernels are
capped by the value of KVM_SUPPORTED_XCR0, and therefore so many subleaves
cannot have appeared on current kernels.

Note, while the Fixes: tag is accurate with respect to the immediate
bug, it's likely that similar bugs in KVM_GET_SUPPORTED_CPUID existed
prior to the refactoring, e.g. Qemu contains a workaround for the broken
KVM_GET_SUPPORTED_CPUID behavior that predates the buggy commit by over
two years.  The Qemu workaround is also likely the main reason the bug
has gone unreported for so long.

Qemu hack:
  commit 76ae317f7c16aec6b469604b1764094870a75470
  Author: Mark McLoughlin <markmc@redhat.com>
  Date:   Tue May 19 18:55:21 2009 +0100

    kvm: work around supported cpuid ioctl() brokenness

    KVM_GET_SUPPORTED_CPUID has been known to fail to return -E2BIG
    when it runs out of entries. Detect this by always trying again
    with a bigger table if the ioctl() fills the table.

Fixes: 831bf664 ("KVM: Refactor and simplify kvm_dev_ioctl_get_supported_cpuid")
Reviewed-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Current SVM implementation does not have support for handling PKU. Guests
running on a host with future AMD cpus that support the feature will read
garbage from the PKRU register and will hit segmentation faults on boot as
memory is getting marked as protected that should not be. Ensure that cpuid
from SVM does not advertise the feature.
Signed-off-by: NJohn Allen <john.allen@amd.com>
Cc: stable@vger.kernel.org
Fixes: 0556cbdc ("x86/pkeys: Don't check if PKRU is zero before writing it")
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Rename bit() to __feature_bit() to give it a more descriptive name, and
add a macro, feature_bit(), to stuff the X68_FEATURE_ prefix to keep
line lengths manageable for code that hardcodes the bit to be retrieved.

No functional change intended.

Cc: Jim Mattson <jmattson@google.com>
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add build-time checks to ensure KVM isn't trying to do a reverse CPUID
lookup on Linux-defined feature bits, along with comments to explain
the gory details of X86_FEATUREs and bit().

No functional change intended.
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The host reports support for the synthetic feature X86_FEATURE_SSBD
when any of the three following hardware features are set:
  CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31]
  CPUID.80000008H:EBX.AMD_SSBD[bit 24]
  CPUID.80000008H:EBX.VIRT_SSBD[bit 25]

Either of the first two hardware features implies the existence of the
IA32_SPEC_CTRL MSR, but CPUID.80000008H:EBX.VIRT_SSBD[bit 25] does
not. Therefore, CPUID.80000008H:EBX.AMD_SSBD[bit 24] should only be
set in the guest if CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31] or
CPUID.80000008H:EBX.AMD_SSBD[bit 24] is set on the host.

Fixes: 4c6903a0 ("KVM: x86: fix reporting of AMD speculation bug CPUID leaf")
Signed-off-by: NJim Mattson <jmattson@google.com>
Reviewed-by: NJacob Xu <jacobhxu@google.com>
Reviewed-by: NPeter Shier <pshier@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Reported-by: NEric Biggers <ebiggers@kernel.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The host reports support for the synthetic feature X86_FEATURE_SSBD
when any of the three following hardware features are set:
  CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31]
  CPUID.80000008H:EBX.AMD_SSBD[bit 24]
  CPUID.80000008H:EBX.VIRT_SSBD[bit 25]

Either of the first two hardware features implies the existence of the
IA32_SPEC_CTRL MSR, but CPUID.80000008H:EBX.VIRT_SSBD[bit 25] does
not. Therefore, CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31] should only be
set in the guest if CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31] or
CPUID.80000008H:EBX.AMD_SSBD[bit 24] is set on the host.

Fixes: 0c54914d ("KVM: x86: use Intel speculation bugs and features as derived in generic x86 code")
Signed-off-by: NJim Mattson <jmattson@google.com>
Reviewed-by: NJacob Xu <jacobhxu@google.com>
Reviewed-by: NPeter Shier <pshier@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Reported-by: NEric Biggers <ebiggers@kernel.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The bounds check was present in KVM_GET_SUPPORTED_CPUID but not
KVM_GET_EMULATED_CPUID.

Reported-by: syzbot+e3f4897236c4eeb8af4f@syzkaller.appspotmail.com
Fixes: 84cffe49 ("kvm: Emulate MOVBE", 2013-10-29)
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Memory encryption support does not have module parameter dependencies
and can be moved into the general x86 cpuid __do_cpuid_ent function.
This changes maintains current behavior of passing through all of
CPUID.8000001F.
Suggested-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPeter Gonda <pgonda@google.com>
Reviewed-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Because KVM always emulates CPUID, the CPUID clear bit
(bit 1) of MSR_IA32_TSX_CTRL must be emulated "manually"
by the hypervisor when performing said emulation.

Right now neither kvm-intel.ko nor kvm-amd.ko implement
MSR_IA32_TSX_CTRL but this will change in the next patch.
Reviewed-by: NJim Mattson <jmattson@google.com>
Tested-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

When the RDPID instruction is supported on the host, enumerate it in
KVM_GET_SUPPORTED_CPUID.
Signed-off-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

I was surprised to see that the guest reported `fxsave_leak' while the
host did not. After digging deeper I noticed that the bits are simply
masked out during enumeration.

The XSAVEERPTR feature is actually a bug fix on AMD which means the
kernel can disable a workaround.

Pass XSAVEERPTR to the guest if available on the host.
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

CLZERO is available to the guest if it is supported on the
host. Therefore, enumerate support for the instruction in
KVM_GET_SUPPORTED_CPUID whenever it is supported on the host.
Signed-off-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

When the guest CPUID information represents an AMD vCPU, return all
zeroes for queries of undefined CPUID leaves, whether or not they are
in range.
Signed-off-by: NJim Mattson <jmattson@google.com>
Fixes: bd22f5cf ("KVM: move and fix substitue search for missing CPUID entries")
Reviewed-by: NMarc Orr <marcorr@google.com>
Reviewed-by: NPeter Shier <pshier@google.com>
Reviewed-by: NJacob Xu <jacobhxu@google.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

For these CPUID leaves, the EDX output is not dependent on the ECX
input (i.e. the SIGNIFCANT_INDEX flag doesn't apply to
EDX). Furthermore, the low byte of the ECX output is always identical
to the low byte of the ECX input. KVM does not produce the correct ECX
and EDX outputs for any undefined subleaves beyond the first.

Special-case these CPUID leaves in kvm_cpuid, so that the ECX and EDX
outputs are properly generated for all undefined subleaves.

Fixes: 07716717 ("KVM: Enhance guest cpuid management")
Fixes: a87f2d3a ("KVM: x86: Add Intel CPUID.1F cpuid emulation support")
Signed-off-by: NJim Mattson <jmattson@google.com>
Reviewed-by: NMarc Orr <marcorr@google.com>
Reviewed-by: NPeter Shier <pshier@google.com>
Reviewed-by: NJacob Xu <jacobhxu@google.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Don't return -E2BIG from __do_cpuid_func when processing function 0BH
or 1FH and the last interesting subleaf occupies the last allocated
entry in the result array.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Fixes: 831bf664 ("KVM: Refactor and simplify kvm_dev_ioctl_get_supported_cpuid")
Signed-off-by: NJim Mattson <jmattson@google.com>
Reviewed-by: NPeter Shier <pshier@google.com>
Reviewed-by: NSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

According to the Intel SDM, volume 2, "CPUID," the index is
significant (or partially significant) for CPUID leaves 0FH, 10H, 12H,
17H, 18H, and 1FH.

Add the corresponding flag to these CPUID leaves in do_host_cpuid().
Signed-off-by: NJim Mattson <jmattson@google.com>
Reviewed-by: NPeter Shier <pshier@google.com>
Reviewed-by: NSteve Rutherford <srutherford@google.com>
Fixes: a87f2d3a ("KVM: x86: Add Intel CPUID.1F cpuid emulation support")
Reviewed-by: NKrish Sadhukhan <krish.sadhukhan@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

UMONITOR, UMWAIT and TPAUSE are a set of user wait instructions.
This patch adds support for user wait instructions in KVM. Availability
of the user wait instructions is indicated by the presence of the CPUID
feature flag WAITPKG CPUID.0x07.0x0:ECX[5]. User wait instructions may
be executed at any privilege level, and use 32bit IA32_UMWAIT_CONTROL MSR
to set the maximum time.

The behavior of user wait instructions in VMX non-root operation is
determined first by the setting of the "enable user wait and pause"
secondary processor-based VM-execution control bit 26.
	If the VM-execution control is 0, UMONITOR/UMWAIT/TPAUSE cause
an invalid-opcode exception (#UD).
	If the VM-execution control is 1, treatment is based on the
setting of the “RDTSC exiting†VM-execution control. Because KVM never
enables RDTSC exiting, if the instruction causes a delay, the amount of
time delayed is called here the physical delay. The physical delay is
first computed by determining the virtual delay. If
IA32_UMWAIT_CONTROL[31:2] is zero, the virtual delay is the value in
EDX:EAX minus the value that RDTSC would return; if
IA32_UMWAIT_CONTROL[31:2] is not zero, the virtual delay is the minimum
of that difference and AND(IA32_UMWAIT_CONTROL,FFFFFFFCH).

Because umwait and tpause can put a (psysical) CPU into a power saving
state, by default we dont't expose it to kvm and enable it only when
guest CPUID has it.

Detailed information about user wait instructions can be found in the
latest Intel 64 and IA-32 Architectures Software Developer's Manual.
Co-developed-by: NJingqi Liu <jingqi.liu@intel.com>
Signed-off-by: NJingqi Liu <jingqi.liu@intel.com>
Signed-off-by: NTao Xu <tao3.xu@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Similar to AMD bits, set the Intel bits from the vendor-independent
feature and bug flags, because KVM_GET_SUPPORTED_CPUID does not care
about the vendor and they should be set on AMD processors as well.
Suggested-by: NJim Mattson <jmattson@google.com>
Reviewed-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>