Re: [Xen-devel] [PATCH] mm: fix LLVM code-generation issue

[Julien Grall <julien.grall@xxxxxxx>]

Hi Jan,

On 23/11/2018 11:33, Jan Beulich wrote:
> > > > On 23.11.18 at 12:23, <roger.pau@xxxxxxxxxx> wrote:
> > Image an AP reads system_state < SYS_STATE_active, then BSP sets
> > system_state = SYS_STATE_active and clears the init mappings, then
> > when the AP tries to read an init variable it would get a page fault.
> As said before - APs are supposed to be quiescent during this
> particular transition of system_state, and the idle scrubbing added
> an exception to that rule. I don't see why such an exception may
> not involve exceptional treatment on the particular reading path.
> Furthermore APs, which may also be brought up at run time, may
> never ever touch init mappings of any kind.
The "supposed" is quite worrying because we have no way to verify that 
assumption until we get a random crash.
Also, the cost of the barrier should be quite cheap over the rest of the 
function.

Cheers,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel