Merge: CVE-2024-53135: KVM: VMX: Bury Intel PT virtualization (guest/host mode) behind CONFIG_BROKEN

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5946

JIRA: https://issues.redhat.com/browse/RHEL-70062
CVE: CVE-2024-53135

```
KVM: VMX: Bury Intel PT virtualization (guest/host mode) behind CONFIG_BROKEN

Hide KVM's pt_mode module param behind CONFIG_BROKEN, i.e. disable support
for virtualizing Intel PT via guest/host mode unless BROKEN=y.  There are
myriad bugs in the implementation, some of which are fatal to the guest,
and others which put the stability and health of the host at risk.

For guest fatalities, the most glaring issue is that KVM fails to ensure
tracing is disabled, and *stays* disabled prior to VM-Enter, which is
necessary as hardware disallows loading (the guest's) RTIT_CTL if tracing
is enabled (enforced via a VMX consistency check).  Per the SDM:

  If the logical processor is operating with Intel PT enabled (if
  IA32_RTIT_CTL.TraceEn = 1) at the time of VM entry, the "load
  IA32_RTIT_CTL" VM-entry control must be 0.

On the host side, KVM doesn't validate the guest CPUID configuration
provided by userspace, and even worse, uses the guest configuration to
decide what MSRs to save/load at VM-Enter and VM-Exit.  E.g. configuring
guest CPUID to enumerate more address ranges than are supported in hardware
will result in KVM trying to passthrough, save, and load non-existent MSRs,
which generates a variety of WARNs, ToPA ERRORs in the host, a potential
deadlock, etc.

Fixes: f99e3da ("KVM: x86: Add Intel PT virtualization work mode")
Cc: [email protected]
Cc: Adrian Hunter <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Reviewed-by: Xiaoyao Li <[email protected]>
Tested-by: Adrian Hunter <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
(cherry picked from commit aa0d42c)
```

Signed-off-by: CKI Backport Bot <[email protected]>
Signed-off-by: Jarod Wilson <[email protected]>

---

<small>Created 2024-12-05 04:49 UTC by backporter - [KWF FAQ](https://red.ht/kernel_workflow_doc) - [Slack #team-kernel-workflow](https://redhat-internal.slack.com/archives/C04LRUPMJQ5) - [Source](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/webhook/utils/backporter.py) - [Documentation](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/docs/README.backporter.md) - [Report an issue](https://gitlab.com/cki-project/kernel-workflow/-/issues/new?issue%5Btitle%5D=backporter%20webhook%20issue)</small>

Approved-by: Jon Maloy <[email protected]>
Approved-by: Vitaly Kuznetsov <[email protected]>
Approved-by: David Arcari <[email protected]>
Approved-by: CKI KWF Bot <[email protected]>

Merged-by: Jan Stancek <[email protected]>

Author: jstancek

arch/x86/kvm/vmx/vmx.c

@@ -215,9 +215,11 @@ module_param(ple_window_shrink, uint, 0444);
 static unsigned int ple_window_max        = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
 module_param(ple_window_max, uint, 0444);
 
-/* Default is SYSTEM mode, 1 for host-guest mode */
+/* Default is SYSTEM mode, 1 for host-guest mode (which is BROKEN) */
 int __read_mostly pt_mode = PT_MODE_SYSTEM;
+#ifdef CONFIG_BROKEN
 module_param(pt_mode, int, S_IRUGO);
+#endif
 
 struct x86_pmu_lbr __ro_after_init vmx_lbr_caps;