Commit 8c56c1a5 authored by Pavel Fedin's avatar Pavel Fedin Committed by Paolo Bonzini
Browse files

memory: emulate ioeventfd 



The ioeventfd mechanism is used by vhost, dataplane, and virtio-pci to
turn guest MMIO/PIO writes into eventfd file descriptor events.  This
allows arbitrary threads to be notified when the guest writes to a
specific MMIO/PIO address.

qtest and TCG do not support ioeventfd because memory writes are not
checked against registered ioeventfds in QEMU.  This patch implements
this in memory_region_dispatch_write() so qtest can use ioeventfd.

Also this patch fixes vhost aborting on some misconfigured old kernels
like 3.18.0 on ARM. It is possible to explicitly enable CONFIG_EVENTFD
in expert settings, while MMIO binding support in KVM will still be
missing.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarPavel Fedin <p.fedin@samsung.com>
Message-Id: <006e01d12377$0b9c2d40$22d487c0$@samsung.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent bc92e4e9

kvm-all.c

+4 −2
Original line number Diff line number Diff line
@@ -1628,8 +1628,10 @@ static int kvm_init(MachineState *ms) 


    kvm_state = s;



    if (kvm_eventfds_allowed) {

        s->memory_listener.listener.eventfd_add = kvm_mem_ioeventfd_add;

        s->memory_listener.listener.eventfd_del = kvm_mem_ioeventfd_del;

    }

    s->memory_listener.listener.coalesced_mmio_add = kvm_coalesce_mmio_region;

    s->memory_listener.listener.coalesced_mmio_del = kvm_uncoalesce_mmio_region;

memory.c

+42 −0
Original line number Diff line number Diff line
@@ -18,12 +18,14 @@ 
#include "exec/ioport.h"

#include "qapi/visitor.h"

#include "qemu/bitops.h"

#include "qemu/error-report.h"

#include "qom/object.h"

#include "trace.h"

#include <assert.h>



#include "exec/memory-internal.h"

#include "exec/ram_addr.h"

#include "sysemu/kvm.h"

#include "sysemu/sysemu.h"



//#define DEBUG_UNASSIGNED
@@ -1136,6 +1138,32 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr, 
    return r;

}



/* Return true if an eventfd was signalled */

static bool memory_region_dispatch_write_eventfds(MemoryRegion *mr,

                                                    hwaddr addr,

                                                    uint64_t data,

                                                    unsigned size,

                                                    MemTxAttrs attrs)

{

    MemoryRegionIoeventfd ioeventfd = {

        .addr = addrrange_make(int128_make64(addr), int128_make64(size)),

        .data = data,

    };

    unsigned i;



    for (i = 0; i < mr->ioeventfd_nb; i++) {

        ioeventfd.match_data = mr->ioeventfds[i].match_data;

        ioeventfd.e = mr->ioeventfds[i].e;



        if (memory_region_ioeventfd_equal(ioeventfd, mr->ioeventfds[i])) {

            event_notifier_set(ioeventfd.e);

            return true;

        }

    }



    return false;

}



MemTxResult memory_region_dispatch_write(MemoryRegion *mr,

                                         hwaddr addr,

                                         uint64_t data,
@@ -1149,6 +1177,11 @@ MemTxResult memory_region_dispatch_write(MemoryRegion *mr, 


    adjust_endianness(mr, &data, size);



    if ((!kvm_eventfds_enabled()) &&

        memory_region_dispatch_write_eventfds(mr, addr, data, size, attrs)) {

        return MEMTX_OK;

    }



    if (mr->ops->write) {

        return access_with_adjusted_size(addr, &data, size,

                                         mr->ops->impl.min_access_size,
@@ -1667,6 +1700,8 @@ void memory_region_clear_global_locking(MemoryRegion *mr) 
    mr->global_locking = false;

}



static bool userspace_eventfd_warning;



void memory_region_add_eventfd(MemoryRegion *mr,

                               hwaddr addr,

                               unsigned size,
@@ -1683,6 +1718,13 @@ void memory_region_add_eventfd(MemoryRegion *mr, 
    };

    unsigned i;



    if (kvm_enabled() && (!(kvm_eventfds_enabled() ||

                            userspace_eventfd_warning))) {

        userspace_eventfd_warning = true;

        error_report("Using eventfd without MMIO binding in KVM. "

                     "Suboptimal performance expected");

    }



    if (size) {

        adjust_endianness(mr, &mrfd.data, size);

    }