On Tue, Aug 07, 2018 at 11:24:34AM +0100, Marc Zyngier wrote: > On 07/08/18 11:05, Dave Martin wrote: > > On Tue, Aug 07, 2018 at 10:33:26AM +0100, Marc Zyngier wrote: > >> It recently came to light that userspace can execute WFI, and that > >> the arm64 kernel doesn trap this event. This sounds rather benign,
Nitpick: "doesn't". > >> but the kernel should decide when it wants to wait for an interrupt, > >> and not userspace. > >> > >> Let's trap WFI and treat it as a way to yield the CPU to another > >> process. [...] > > I can't think of a legitimate reason for userspace to execute WFI > > however. Userspace doesn't have interrupts under Linux, so it makes > > no sense to wait for one. > > > > Have we seen anybody using WFI in userspace? It may be cleaner to > > map this to SIGILL rather than be permissive and regret it later. > > I couldn't find any user, and I'm happy to just send userspace to hell > in that case. But it could also been said that since it was never > prevented, it is a de-facto ABI. I wouldn't really go as far as SIGILL on WFI. I think the patch is fine as it is. In case Will plans to merge it: Acked-by: Catalin Marinas <catalin.mari...@arm.com>
