Re: [Xen-devel] [PATCH 20/27] tools/libxl: Infrastructure for writing a v2 stream

[Yang Hongyang <yanghy@xxxxxxxxxxxxxx>]

On 06/15/2015 09:44 PM, Andrew Cooper wrote:
[...]
> +
> +static void write_emulator_record(libxl__egc *egc,
> +                                  libxl__stream_write_state *stream)
> +{
> +    libxl__domain_suspend_state *dss = CONTAINER_OF(stream, *dss, sws);
> +    libxl__datacopier_state *dc = &stream->dc;
> +    STATE_AO_GC(stream->ao);
> +    struct libxl_sr_rec_hdr rec = { REC_TYPE_EMULATOR_CONTEXT, 0 };
> +    struct libxl_sr_emulator_hdr ehdr = { 0 };
> +    struct stat st;
> +    int ret = 0;
> +    uint32_t qemu_state_len;
> +
> +    assert(dss->type == LIBXL_DOMAIN_TYPE_HVM);
> +
> +    /* Convenience aliases */
> +    const char *const filename = dss->dm_savefile;
> +    const uint32_t domid = dss->domid;
> +
> +    switch(libxl__device_model_version_running(gc, domid)) {
> +    case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
> +        ehdr.id = EMULATOR_QEMU_TRADITIONAL;
> +        break;
> +
> +    case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
> +        ehdr.id = EMULATOR_QEMU_UPSTREAM;
> +        break;
> +
> +    default:
> +        ret = ERROR_FAIL;
> +        goto err;
> +    }
> +
> +    ret = libxl__domain_suspend_device_model(gc, dss);
This is no longer needed, the suspend callback already called
this function and the emulator context already saved to a file.

This call will cause Primary's emulator stop under Remus.
postcopy callback will resume primary. then in checkpoint
callback, we shouldn't suspend device model.

> +    if (ret)
> +        goto err;
> +
> +    dc->readwhat = GCSPRINTF("qemu save file %s", filename);
> +    dc->copywhat = "emulator record";
> +    dc->writewhat = "save/migration stream";
> +    dc->callback = emulator_body_done;
> +
> +    dc->readfd = open(filename, O_RDONLY);
> +    if (dc->readfd < 0) {
> +        LOGE(ERROR, "unable to open %s", dc->readwhat);
> +        goto err;
> +    }
> +
> +    if (fstat(dc->readfd, &st))
> +    {
> +        LOGE(ERROR, "unable to fstat %s", dc->readwhat);
> +        goto err;
> +    }
> +
> +    if (!S_ISREG(st.st_mode)) {
> +        LOG(ERROR, "%s is not a plain file!", dc->readwhat);
> +        goto err;
> +    }
> +
> +    qemu_state_len = st.st_size;
> +    rec.length = qemu_state_len + sizeof(ehdr);
> +
> +    ret = libxl__datacopier_start(dc);
> +    if (ret)
> +        goto err;
> +
> +    libxl__datacopier_prefixdata(egc, dc, &rec, sizeof(rec));
> +    libxl__datacopier_prefixdata(egc, dc, &ehdr, sizeof(ehdr));
> +
> +    stream->padding = ROUNDUP(qemu_state_len, REC_ALIGN_ORDER) - 
> qemu_state_len;
> +    return;
> +
> + err:
> +    assert(ret);
> +    stream_failed(egc, stream, ret);
> +}
> +
> +static void emulator_body_done(libxl__egc *egc,
> +                               libxl__datacopier_state *dc,
> +                               int onwrite, int errnoval)
> +{
> +    libxl__stream_write_state *stream = CONTAINER_OF(dc, *stream, dc);
> +    STATE_AO_GC(stream->ao);
> +    int ret = 0;
> +
> +    if (onwrite || errnoval) {
> +        ret = ERROR_FAIL;
> +        goto err;
> +    }
> +
> +    dc->readwhat = "";
> +    dc->readfd = -1;
> +
> +    if (stream->padding) {
> +        assert(stream->padding < (1U << REC_ALIGN_ORDER));
> +
> +        dc->copywhat = "emulator padding";
> +        dc->writewhat = "save/migration stream";
> +        dc->callback = emulator_padding_done;
> +
> +        ret = libxl__datacopier_start(dc);
> +        if (ret)
> +            goto err;
> +
> +        libxl__datacopier_prefixdata(egc, dc, zero_padding, stream->padding);
> +        return;
> +    }
> +
> +    emulator_padding_done(egc, dc, 0, 0);
> +    return;
> +
> + err:
> +    assert(ret);
> +    stream_failed(egc, stream, ret);
> +}
> +
> +static void emulator_padding_done(libxl__egc *egc,
> +                                  libxl__datacopier_state *dc,
> +                                  int onwrite, int errnoval)
> +{
> +    libxl__stream_write_state *stream = CONTAINER_OF(dc, *stream, dc);
> +    STATE_AO_GC(stream->ao);
> +    int ret = 0;
> +
> +    if (onwrite || errnoval) {
> +        ret = ERROR_FAIL;
> +        goto err;
> +    }
> +
> +    write_end_record(egc, stream);
> +    return;
> +
> + err:
> +    assert(ret);
> +    stream_failed(egc, stream, ret);
> +}
> +
> +static void write_end_record(libxl__egc *egc,
> +                             libxl__stream_write_state *stream)
> +{
> +    libxl__datacopier_state *dc = &stream->dc;
> +    STATE_AO_GC(stream->ao);
> +    struct libxl_sr_rec_hdr rec = { REC_TYPE_END, 0 };
> +    int ret = 0;
> +
> +    dc->copywhat = "suspend footer";
> +    dc->writewhat = "save/migration stream";
> +    dc->callback = end_record_done;
> +
> +    ret = libxl__datacopier_start(dc);
> +    if (ret)
> +        goto err;
> +
> +    libxl__datacopier_prefixdata(egc, dc, &rec, sizeof(rec));
> +    return;
> +
> + err:
> +    assert(ret);
> +    stream_failed(egc, stream, ret);
> +}
> +
> +static void end_record_done(libxl__egc *egc,
> +                            libxl__datacopier_state *dc,
> +                            int onwrite, int errnoval)
> +{
> +    libxl__stream_write_state *stream = CONTAINER_OF(dc, *stream, dc);
> +    STATE_AO_GC(stream->ao);
> +    int ret = 0;
> +
> +    if (onwrite || errnoval) {
> +        ret = ERROR_FAIL;
> +        goto err;
> +    }
> +
> +    stream_success(egc, stream);
> +    return;
> +
> + err:
> +    assert(ret);
> +    stream_failed(egc, stream, ret);
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
--
Thanks,
Yang.

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