kvm: don't take vcpu mutex for obviously invalid vcpu ioctls
commit7a246504ca22670125459b51910c875c7099ca97
authorDavid Matlack <dmatlack@google.com>
Fri, 19 Sep 2014 23:03:25 +0000 (19 16:03 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 30 Oct 2014 16:40:10 +0000 (30 09:40 -0700)
treea4509a379d306dce8e25414287cdb7714d644c6c
parente58afde2c981b6bc6335620c52f0a0b680cf7306
kvm: don't take vcpu mutex for obviously invalid vcpu ioctls

commit 2ea75be3219571d0ec009ce20d9971e54af96e09 upstream.

vcpu ioctls can hang the calling thread if issued while a vcpu is running.
However, invalid ioctls can happen when userspace tries to probe the kind
of file descriptors (e.g. isatty() calls ioctl(TCGETS)); in that case,
we know the ioctl is going to be rejected as invalid anyway and we can
fail before trying to take the vcpu mutex.

This patch does not change functionality, it just makes invalid ioctls
fail faster.

Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
virt/kvm/kvm_main.c