On Tue, Apr 25, 2017 at 05:37:50PM +0200, Igor Mammedov wrote: > Since 2.7 commit (b2a575a Add optionrom compatible with fw_cfg DMA version) > regressed migration during firmware exection time by > abusing fwcfg.dma_enabled property to decide loading > dma version of option rom AND by mistake disabling DMA > for 2.6 and earlier globally instead of only for option rom. > > so 2.6 machine type guest is broken when it already runs > firmware in DMA mode but migrated to qemu-2.7(pc-2.6) > at that time; > > a) qemu-2.6:pc2.6 (fwcfg.dma=on,firmware=dma,oprom=ioport) > b) qemu-2.7:pc2.6 (fwcfg.dma=off,firmware=ioport,oprom=ioport) > > to: a b > from > a OK FAIL > b OK OK > > So we currently have broken forward migration from > qemu-2.6 to qemu-2.[789] that however could be fixed > for 2.10 by re-enabling DMA for 2.[56] machine types > and allowing dma capable option rom only since 2.7. > As result qemu should end up with: > > c) qemu-2.10:pc2.6 (fwcfg.dma=on,firmware=dma,oprom=ioport) > > to: a b c > from > a OK FAIL OK > b OK OK OK > c OK FAIL OK > > where forward migration from qemu-2.6 to qemu-2.10 should > work again leaving only qemu-2.[789]:pc-2.6 broken. > > Reported-by: Eduardo Habkost <ehabk...@redhat.com> > Analyzed-by: Laszlo Ersek <ler...@redhat.com> > Signed-off-by: Igor Mammedov <imamm...@redhat.com> > Reviewed-by: Laszlo Ersek <ler...@redhat.com>
Reviewed-by: Eduardo Habkost <ehabk...@redhat.com> -- Eduardo
