On Tue, Mar 29, 2022 at 01:12:33AM +0200, Andrea Parri wrote: > On Sun, Mar 27, 2022 at 08:25:10AM -0700, Michael Kelley wrote: > > When reading a packet from a host-to-guest ring buffer, there is no > > memory barrier between reading the write index (to see if there is > > a packet to read) and reading the contents of the packet. The Hyper-V > > host uses store-release when updating the write index to ensure that > > writes of the packet data are completed first. On the guest side, > > the processor can reorder and read the packet data before the write > > index, and sometimes get stale packet data. Getting such stale packet > > data has been observed in a reproducible case in a VM on ARM64. > > > > Fix this by using virt_load_acquire() to read the write index, > > ensuring that reads of the packet data cannot be reordered > > before it. Preventing such reordering is logically correct, and > > with this change, getting stale data can no longer be reproduced. > > > > Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> > > Reviewed-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx> > > Nit: subject prefix -> "Drivers: hv: vmbus:". Applied to hyperv-fixes. Thanks. > > Thanks, > Andrea
