Am 03.06.2020 um 12:22 hat Pavel Dovgalyuk geschrieben: > From: Pavel Dovgalyuk <pavel.dovga...@gmail.com> > > Windows guest sometimes makes DMA requests with overlapping > target addresses. This leads to the following structure of iov for > the block driver: > > addr size1 > addr size2 > addr size3 > > It means that three adjacent disk blocks should be read into the same > memory buffer. Windows does not expects anything from these bytes > (should it be data from the first block, or the last one, or some mix), > but uses them somehow. It leads to non-determinism of the guest execution, > because block driver does not preserve any order of reading. > > This situation was discusses in the mailing list at least twice: > https://lists.gnu.org/archive/html/qemu-devel/2010-09/msg01996.html > https://lists.gnu.org/archive/html/qemu-devel/2020-02/msg05185.html > > This patch makes such disk reads deterministic in icount mode. > It splits the whole request into several parts. Parts may overlap, > but SGs inside one part do not overlap. > Parts that are processed later overwrite the prior ones in case > of overlapping. > > Examples for different SG part sequences: > > 1) > A1 1000 > A2 1000 > A1 1000 > A3 1000 > -> > One request is split into two. > A1 1000 > A2 1000 > -- > A1 1000 > A3 1000 > > 2) > A1 800 > A2 1000 > A1 1000 > -> > A1 800 > A2 1000 > -- > A1 1000 > > Signed-off-by: Pavel Dovgalyuk <pavel.dovga...@ispras.ru>
Thanks, applied to the block branch. Kevin
