KVM: x86: Unconditionally reset MMU context when emulating INIT

Force an MMU reset when emulating an INIT even if paging was already
disabled, as the MMU page role includes guest_mode (L2), i.e. an INIT while
L2 is running with CR0.PG=0 will result in KVM running L1 with a stale MMU
context.

Alternatively, the reset could be scoped strictly to paging being enabled
or L2 being active, but SMM is also encoded in the page role.  Even though
it _should_ be impossible for the vCPU to be INIT'd while SMM is active,
there's zero value in not handling SMM.  At that point, the only scenario
where KVM _doesn't_ need to reset the MMU context is on an INIT with the
vCPU running in Real Mode or Unpaged Protect Mode, and while INIT in those
modes is somewhat common, it's far from a hot path and re-initializing the
MMU is not expensive, especially when the role isn't changing (KVM elides
most of the re-configuration in that case).

Note, like the Fixes commit, this bug only affects nested SVM as INIT is an
unconditional intercept on VMX, i.e. it's impossible to emulate INIT while
L2 is active.

Temporarily keep the guest TLB flush when CR0.PG is being cleared even
though it is fully redundant with the flush that is emitted on all INIT
events (KVM itself only does RESET when a vCPU is being created, i.e. when
CR0.PG must be '0').

Fixes: ed129ec9057f ("KVM: x86: forcibly leave nested mode on vCPU reset")
Reported-by: Stefan Teodorescu <fane@google.com>
Reported-by: Oren Yomtov <thenameisoren@gmail.com>
Reported-by: Chris Mason <mason@kernel.org>
Cc: stable@vger.kernel.org
Cc: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20261022015407.279870-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

0 files changed, 0 insertions, 0 deletions