KVM: x86: Don't WARN if userspace mucks with RCX during string I/O exit

commit d07898eaf3 upstream.

Replace a WARN with a comment to call out that userspace can modify RCX
during an exit to userspace to handle string I/O.  KVM doesn't actually
support changing the rep count during an exit, i.e. the scenario can be
ignored, but the WARN needs to go as it's trivial to trigger from
userspace.

Cc: stable@vger.kernel.org
Fixes: 3b27de2718 ("KVM: x86: split the two parts of emulator_pio_in")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211025201311.1881846-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sean Christopherson 2021-10-25 13:13:10 -07:00 • committed by Greg Kroah-Hartman
commit eea80da347