Re: [PATCH v1] kernel: add a simple timer based software watchpoint

[Feng Tang]

On Fri, Jun 26, 2026 at 09:56:22AM +0800, Feng Tang wrote:
 
> > > ability to do the virtual to physical address translation instantly to
> > > watch a _physical_ address. So I guess, not able to watchpoint a physical
> > > address may be common for HW debuggers (I could be very wrong).
> > 
> > If the hardware debugger and the underlying CPU facility (ETM on ARM64
> > IIRC) does not support triggers on physical addresses and you already
> > concluded from other information that the problem is in the BIOS, then
> > tracing the kernel with it's virt/phys translation is not going to
> > work. You obviously have to use the BIOS translation which might be very
> > different, no?

Forgot to metion, the problem of BIOS was actually enabling some experimental
silicon feature, which it should not for this hardware, and then the BIOS
wasn't involved in the detail context of the issue.

Thanks,
Feng

> 
> I didn't explain the issue clearly. The order for solving this issue was,
> we first used this method to halt (while (1) dead loop) the system when
> detecting the memory corruption,  silicon engineers gathered hardware
> traces, then root caused it. Before that, we didn't know it's a BIOS issue,
> as the initial symptom was random user space "segmentation fault"