• Christian Borntraeger's avatar
    hvc_console: rework setup to replace irq functions with callbacks · 611e097d
    Christian Borntraeger authored
    This patch tries to change hvc_console to not use request_irq/free_irq if
    the backend does not use irqs. This allows virtio_console to use hvc_console
    without having a linker reference to request_irq/free_irq.
    
    In addition, together with patch 2/3 it improves the performance for virtio
    console input. (an earlier version of this patch was tested by Yajin on lguest)
    
    The irq specific code is moved to hvc_irq.c and selected by the drivers that
    use irqs (System p, System i, XEN).
    
    I replaced "int irq" with the opaque "int data". The request_irq and
    free_irq calls are replaced with notifier_add and notifier_del. I have also
    changed the code a bit to call the notifier_add and notifier_del inside the
    spinlock area as the callbacks are found via hp->ops.
    
    Changes since last version:
    o remove ifdef
    o reintroduce "irq_requested" as "notified"
    o cleanups, sparse..
    
    I did not move the timer based polling into a separate polling scheme. I
    played with several variants, but it seems we need to sleep/schedule in
    a thread even for irq based consoles, as there are throttleing and buffer
    size constraints.
    
    I also kept hvc_struct defined in hvc_console.h so that hvc_irq.c can access
    the irq_requested element.
    
    Feedback is appreciated. virtio_console is currently the only available console
    for kvm on s390. I plan to push this change as soon as all affected parties
    agree on it. I would love to get test results from System p, Xen etc.
    Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
    Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
    611e097d
hvc_console.c 20.1 KB