Re: [RFC PATCH V2 4/7] x86/hw_breakpoint: Prevent data breakpoints on user_pcid_flush_mask

From: Andy Lutomirski
Date: Tue May 26 2020 - 00:17:49 EST

On Mon, May 25, 2020 at 6:42 PM Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> wrote:
> The percpu user_pcid_flush_mask is used for CPU entry
> If a data breakpoint on it, it will cause an unwanted #DB.
> Protect the full cpu_tlbstate structure to be sure.
> There are some other percpu data used in CPU entry, but they are
> either in already-protected cpu_tss_rw or are safe to trigger #DB
> (espfix_waddr, espfix_stack).

How hard would it be to rework this to have DECLARE_PERCPU_NODEBUG()
and DEFINE_PERCPU_NODEBUG() or similar?