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Sean Christopherson c3742319d0 KVM: VMX: Bury Intel PT virtualization (guest/host mode) behind CONFIG_BROKEN
commit aa0d42cacf093a6fcca872edc954f6f812926a17 upstream.

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: f99e3daf94 ("KVM: x86: Add Intel PT virtualization work mode")
Cc: stable@vger.kernel.org
Cc: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Tested-by: Adrian Hunter <adrian.hunter@intel.com>
Message-ID: <20241101185031.1799556-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-12-14 19:44:18 +01:00
arch KVM: VMX: Bury Intel PT virtualization (guest/host mode) behind CONFIG_BROKEN 2024-12-14 19:44:18 +01:00
block
certs
crypto
Documentation
drivers net/mlx5e: kTLS, Fix incorrect page refcounting 2024-12-14 19:44:18 +01:00
fs ocfs2: uncache inode which has failed entering the group 2024-12-14 19:44:18 +01:00
include mm: add remap_pfn_range_notrack 2024-11-17 14:58:53 +01:00
init
ipc
kernel
lib
LICENSES
mm mm: avoid leaving partial pfn mappings around in error case 2024-11-17 14:58:53 +01:00
net netlink: terminate outstanding dump on socket close 2024-12-14 19:44:18 +01:00
samples
scripts
security
sound sound: Make CONFIG_SND depend on INDIRECT_IOMEM instead of UML 2024-11-17 14:58:53 +01:00
tools
usr
virt
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.cocciconfig
.get_maintainer.ignore
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COPYING
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Makefile Linux 5.4.286 2024-11-17 14:58:53 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.