Re: [Qemu-devel] [PATCH] notdirty_mem_write: implement 8-byte accesses

[Andrew Baumann]

> From: Andrew Baumann
> Sent: Friday, 13 October 2017 11:19
> 
> Aligned 8-byte memory writes by a 64-bit target on a 64-bit host should
> always turn into atomic 8-byte writes on the host, however if we missed
> in the softmmu, and the TLB line was marked as not dirty, then we
> would end up tearing the 8-byte write into two 4-byte writes in
> access_with_adjusted_size().
> 
> Signed-off-by: Andrew Baumann <address@hidden>
> ---
> This manifested as a race in lock-free synchronisation with an aarch64
> Windows guest on an x86-64 host (with multithreaded TCG).
> 
>  exec.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)

By the way, I noticed that watch_mem_ops are also 4-byte only. I suspect the 
same fix may be needed there?

Andrew