Adopting the Linux Kernel Memory Model in Xen?

[Julien Grall <julien@xxxxxxx>]

Hi all,

At the moment, Xen doesn't have a formal memory model. Instead, we are 
relying on intuitions. This can lead to heated discussion on what can a 
processor/compiler do or not.
We also have some helpers that nearly do the same (such as 
{read,write}_atomic() vs ACCESS_ONCE()) with no clear understanding 
where to use which.
In the past few years, Linux community spent a lot of time to write down 
their memory model and make the compiler communities aware of it (see 
[1], [2]).
There are a few reasons I can see for adopting LKMM:
   - Xen borrows a fair amount of code from Linux;
   - There are efforts to standardize it;
   - This will allow us to streamline the discussion.

Any thoughts?

Cheers,

[1] https://www.kernel.org/doc/Documentation/memory-barriers.txt
[2] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p0124r7.html


--
Julien Grall