Merge tag 'kvm-x86-misc-6.17' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.17

 - Prevert the host's DEBUGCTL.FREEZE_IN_SMM (Intel only) when running the
   guest.  Failure to honor FREEZE_IN_SMM can bleed host state into the guest.

 - Explicitly check vmcs12.GUEST_DEBUGCTL on nested VM-Enter (Intel only) to
   prevent L1 from running L2 with features that KVM doesn't support, e.g. BTF.

 - Intercept SPEC_CTRL on AMD if the MSR shouldn't exist according to the
   vCPU's CPUID model.

 - Rework the MSR interception code so that the SVM and VMX APIs are more or
   less identical.

 - Recalculate all MSR intercepts from the "source" on MSR filter changes, and
   drop the dedicated "shadow" bitmaps (and their awful "max" size defines).

 - WARN and reject loading kvm-amd.ko instead of panicking the kernel if the
   nested SVM MSRPM offsets tracker can't handle an MSR.

 - Advertise support for LKGS (Load Kernel GS base), a new instruction that's
   loosely related to FRED, but is supported and enumerated independently.

 - Fix a user-triggerable WARN that syzkaller found by stuffing INIT_RECEIVED,
   a.k.a. WFS, and then putting the vCPU into VMX Root Mode (post-VMXON).  Use
   the same approach KVM uses for dealing with "impossible" emulation when
   running a !URG guest, and simply wait until KVM_RUN to detect that the vCPU
   has architecturally impossible state.

 - Add KVM_X86_DISABLE_EXITS_APERFMPERF to allow disabling interception of
   APERF/MPERF reads, so that a "properly" configured VM can "virtualize"
   APERF/MPERF (with many caveats).

 - Reject KVM_SET_TSC_KHZ if vCPUs have been created, as changing the "default"
   frequency is unsupported for VMs with a "secure" TSC, and there's no known
   use case for changing the default frequency for other VM types.

tools/include/uapi/linux/kvm.h

@@ -618,6 +618,7 @@ struct kvm_ioeventfd {
 #define KVM_X86_DISABLE_EXITS_HLT            (1 << 1)
 #define KVM_X86_DISABLE_EXITS_PAUSE          (1 << 2)
 #define KVM_X86_DISABLE_EXITS_CSTATE         (1 << 3)
+#define KVM_X86_DISABLE_EXITS_APERFMPERF     (1 << 4)
 
 /* for KVM_ENABLE_CAP */
 struct kvm_enable_cap {