Commit 9b88cd76 authored by Cédric Le Goater's avatar Cédric Le Goater Committed by David Gibson
Browse files

spapr/xive: introduce a VM state change handler 



This handler is in charge of stabilizing the flow of event notifications
in the XIVE controller before migrating a guest. This is a requirement
before transferring the guest EQ pages to a destination.

When the VM is stopped, the handler sets the source PQs to PENDING to
stop the flow of events and to possibly catch a triggered interrupt
occuring while the VM is stopped. Their previous state is saved. The
XIVE controller is then synced through KVM to flush any in-flight
event notification and to stabilize the EQs. At this stage, the EQ
pages are marked dirty to make sure the EQ pages are transferred if a
migration sequence is in progress.

The previous configuration of the sources is restored when the VM
resumes, after a migration or a stop. If an interrupt was queued while
the VM was stopped, the handler simply generates the missing trigger.

Signed-off-by: default avatarCédric Le Goater <clg@kaod.org>
Reviewed-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Message-Id: <20190513084245.25755-6-clg@kaod.org>
Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
parent 7bfc759c

hw/intc/spapr_xive_kvm.c

+95 −1
Original line number Diff line number Diff line
@@ -433,9 +433,100 @@ static void kvmppc_xive_get_queues(SpaprXive *xive, Error **errp) 
    }

}



/*

 * The primary goal of the XIVE VM change handler is to mark the EQ

 * pages dirty when all XIVE event notifications have stopped.

 *

 * Whenever the VM is stopped, the VM change handler sets the source

 * PQs to PENDING to stop the flow of events and to possibly catch a

 * triggered interrupt occuring while the VM is stopped. The previous

 * state is saved in anticipation of a migration. The XIVE controller

 * is then synced through KVM to flush any in-flight event

 * notification and stabilize the EQs.

 *

 * At this stage, we can mark the EQ page dirty and let a migration

 * sequence transfer the EQ pages to the destination, which is done

 * just after the stop state.

 *

 * The previous configuration of the sources is restored when the VM

 * runs again. If an interrupt was queued while the VM was stopped,

 * simply generate a trigger.

 */

static void kvmppc_xive_change_state_handler(void *opaque, int running,

                                             RunState state)

{

    SpaprXive *xive = opaque;

    XiveSource *xsrc = &xive->source;

    Error *local_err = NULL;

    int i;



    /*

     * Restore the sources to their initial state. This is called when

     * the VM resumes after a stop or a migration.

     */

    if (running) {

        for (i = 0; i < xsrc->nr_irqs; i++) {

            uint8_t pq = xive_source_esb_get(xsrc, i);

            uint8_t old_pq;



            old_pq = xive_esb_read(xsrc, i, XIVE_ESB_SET_PQ_00 + (pq << 8));



            /*

             * An interrupt was queued while the VM was stopped,

             * generate a trigger.

             */

            if (pq == XIVE_ESB_RESET && old_pq == XIVE_ESB_QUEUED) {

                xive_esb_trigger(xsrc, i);

            }

        }



        return;

    }



    /*

     * Mask the sources, to stop the flow of event notifications, and

     * save the PQs locally in the XiveSource object. The XiveSource

     * state will be collected later on by its vmstate handler if a

     * migration is in progress.

     */

    for (i = 0; i < xsrc->nr_irqs; i++) {

        uint8_t pq = xive_esb_read(xsrc, i, XIVE_ESB_GET);



        /*

         * PQ is set to PENDING to possibly catch a triggered

         * interrupt occuring while the VM is stopped (hotplug event

         * for instance) .

         */

        if (pq != XIVE_ESB_OFF) {

            pq = xive_esb_read(xsrc, i, XIVE_ESB_SET_PQ_10);

        }

        xive_source_esb_set(xsrc, i, pq);

    }



    /*

     * Sync the XIVE controller in KVM, to flush in-flight event

     * notification that should be enqueued in the EQs and mark the

     * XIVE EQ pages dirty to collect all updates.

     */

    kvm_device_access(xive->fd, KVM_DEV_XIVE_GRP_CTRL,

                      KVM_DEV_XIVE_EQ_SYNC, NULL, true, &local_err);

    if (local_err) {

        error_report_err(local_err);

        return;

    }

}



void kvmppc_xive_synchronize_state(SpaprXive *xive, Error **errp)

{

    /*

     * When the VM is stopped, the sources are masked and the previous

     * state is saved in anticipation of a migration. We should not

     * synchronize the source state in that case else we will override

     * the saved state.

     */

    if (runstate_is_running()) {

        kvmppc_xive_source_get_state(&xive->source);

    }



    /* EAT: there is no extra state to query from KVM */
@@ -515,6 +606,9 @@ void kvmppc_xive_connect(SpaprXive *xive, Error **errp) 
                                      "xive.tima", tima_len, xive->tm_mmap);

    sysbus_init_mmio(SYS_BUS_DEVICE(xive), &xive->tm_mmio);



    xive->change = qemu_add_vm_change_state_handler(

        kvmppc_xive_change_state_handler, xive);



    kvm_kernel_irqchip = true;

    kvm_msi_via_irqfd_allowed = true;

    kvm_gsi_direct_mapping = true;

include/hw/ppc/spapr_xive.h

+1 −0
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ typedef struct SpaprXive { 
    /* KVM support */

    int           fd;

    void          *tm_mmap;

    VMChangeStateEntry *change;

} SpaprXive;



/*