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Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support t
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice |
Date: |
Thu, 12 Jun 2014 12:39:27 +0200 |
> Am 12.06.2014 um 12:14 schrieb Greg Kurz <address@hidden>:
>
> On Thu, 12 Jun 2014 11:43:20 +0200
> Alexander Graf <address@hidden> wrote:
>
>>
>>> On 12.06.14 11:39, Paolo Bonzini wrote:
>>> Il 12/06/2014 11:37, Michael S. Tsirkin ha scritto:
>>>> Maybe just drop unnecessary stuff for new machine types?
>>>> Then we won't need hacks to migrate it.
>>>
>>> For any machine type it's trivial to migrate it. All machine types
>>> including old ones can disregard the migrated values.
>>
>> How about a patch like this before the actual LE awareness ones? With
>> this we should make virtio-serial config space completely independent of
>> live migration.
>>
>> Also since QEMU versions that do read these swapped values during
>> migration are not bi-endian aware, we can never get into a case where a
>> cross-endian save needs to be considered ;).
>>
>>
>> Alex
>>
>>
>> diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
>> index 2b647b6..73cb9b7 100644
>> --- a/hw/char/virtio-serial-bus.c
>> +++ b/hw/char/virtio-serial-bus.c
>> @@ -670,6 +670,7 @@ static int virtio_serial_load(QEMUFile *f, void
>> *opaque, int version_id)
>> uint32_t max_nr_ports, nr_active_ports, ports_map;
>> unsigned int i;
>> int ret;
>> + uint32_t tmp;
>>
>> if (version_id > 3) {
>> return -EINVAL;
>> @@ -685,17 +686,12 @@ static int virtio_serial_load(QEMUFile *f, void
>> *opaque, int version_id)
>> return 0;
>> }
>>
>> - /* The config space */
>> - qemu_get_be16s(f, &s->config.cols);
>> - qemu_get_be16s(f, &s->config.rows);
>> -
>> - qemu_get_be32s(f, &max_nr_ports);
>> - tswap32s(&max_nr_ports);
>> - if (max_nr_ports > tswap32(s->config.max_nr_ports)) {
>> - /* Source could have had more ports than us. Fail migration. */
>> - return -EINVAL;
>> - }
>> + /* Unused */
>> + qemu_get_be16s(f, &tmp);
>> + qemu_get_be16s(f, &tmp);
>> + qemu_get_be32s(f, &tmp);
>>
>> + max_nr_ports = tswap32(s->config.max_nr_ports);
>> for (i = 0; i < (max_nr_ports + 31) / 32; i++) {
>> qemu_get_be32s(f, &ports_map);
>
> For the moment, we have 0 < max_nr_ports < 32 so the source
> machine only stores a single 32 bit value... If this limit
> gets raised, we can end up sending more than that... and
> only the source machine max_nr_ports value can give the
> information...
Why? This value only ever gets set in realize, so it will not change during the
lifetime of the device - which means we don't need to migrate it.
Alex
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, (continued)
Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Paolo Bonzini, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Alexander Graf, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Greg Kurz, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Paolo Bonzini, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Michael S. Tsirkin, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Paolo Bonzini, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Alexander Graf, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Greg Kurz, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice,
Alexander Graf <=
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Greg Kurz, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Alexander Graf, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Michael S. Tsirkin, 2014/06/12
- Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Greg Kurz, 2014/06/12
Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Michael S. Tsirkin, 2014/06/12
Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Michael S. Tsirkin, 2014/06/12
Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Michael S. Tsirkin, 2014/06/12