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:". Thanks, Andrea
