fw_cfg: unbreak migration compatibility for 2.4 and earlier machines
When I reviewed Marc's fw_cfg DMA patches, I completely missed that the way we set dma_enabled would break migration. Gerd explained the right way (see reference below): dma_enabled should be set to true by default, and only true->false transitions should be possible: - when the user requests that with -global fw_cfg_mem.dma_enabled=off or -global fw_cfg_io.dma_enabled=off as appropriate for the platform, - when HW_COMPAT_2_4 dictates it, - when board code initializes fw_cfg without requesting DMA support. Cc: Marc Marí <markmb@redhat.com> Cc: Gerd Hoffmann <kraxel@redhat.com> Cc: Alexandre DERUMIER <aderumier@odiso.com> Cc: qemu-stable@nongnu.org Ref: http://thread.gmane.org/gmane.comp.emulators.qemu/390272/focus=391042 Ref: https://bugs.launchpad.net/qemu/+bug/1536487Suggested-by: NGerd Hoffmann <kraxel@redhat.com> Signed-off-by: NLaszlo Ersek <lersek@redhat.com> Message-id: 1455823860-22268-1-git-send-email-lersek@redhat.com Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
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