This issue that xdcbt is supposed to solve happens at a completely different level. Performing a full disk to tape backup would slow systems down because the entire disk would be copied through the OS buffer cache, evicting data used by other processes.
The UNIX fix for this was to use a raw device or O_DIRECT to bypass the buffer cache.
Maybe Intel's new cache partitioning feature offers a similar fix, see:
Actually in the comments someone mentions using cache partitioning for security. Maybe the threads used by jit code could be placed in their cache partition to avoid some of Spectre.
The UNIX fix for this was to use a raw device or O_DIRECT to bypass the buffer cache.
Maybe Intel's new cache partitioning feature offers a similar fix, see:
https://lwn.net/Articles/694800/
Actually in the comments someone mentions using cache partitioning for security. Maybe the threads used by jit code could be placed in their cache partition to avoid some of Spectre.