Re: [PATCH v3] x86-64/Xen: fix stack switching

[Andy Lutomirski]

On Tue, Jan 15, 2019 at 8:58 AM Jan Beulich <JBeulich@xxxxxxxx> wrote:
>
> While in the native case entry into the kernel happens on the trampoline
> stack, PV Xen kernels get entered with the current thread stack right
> away. Hence source and destination stacks are identical in that case,
> and special care is needed.
>
> Other than in sync_regs() the copying done on the INT80 path isn't
> NMI / #MC safe, as either of these events occurring in the middle of the
> stack copying would clobber data on the (source) stack.
>
> I'm not altering the similar code in interrupt_entry() and nmi(), as
> those code paths are unreachable afaict when running PV Xen guests.


Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>