Re: [PATCH RFT RFC] usb: xhci: Kill hosts with HCE or HSE on command timeout

[Michal Pecio]

On Sun, 3 May 2026 00:36:27 -0300, Desnes Nunes wrote:
> On Sat, May 2, 2026 at 6:55 PM Michal Pecio <michal.pecio@xxxxxxxxx> wrote:
> > On Sat, 2 May 2026 08:38:34 -0300, Desnes Nunes wrote:  
> > > Kdump doesn't run and no vmcore is produced:  
> > Is the kdump kernel not launched, or does it crash during boot?
> > The latter would make sense if there is some problem with the code.  
> 
> Kdump kernel didn't launch at all, thus no vmcore was produced.

Well, that's weird. But it seems you have serial console enabled so
I guess you should know whether it fails to start or crashes.

> > But I don't understand how patching xhci-hcd could possibly have
> > any effect on the former. Does this new code execute at all? Does
> > "kill the damn thing" ever appear in dmesg?  
> 
> Both kernels booted normally: the first one checking HSE after USBSTS
> was logged on xhci_handle_command_timeout(), as well as this new code
> checking for ring state or the HSE and HCE bits.
> Since kdump didn't start, the message "kill the damn thing" never got
> a chance to appear on crashkernel's dmesg.

It could show on the main kernel before the panic is triggered, if the
main kernel was patched too. Maybe they are the same kernel binary?

I'm trying to come up with any conceivable theory how patching xhci-hcd
could prevent the kdump kernel from loading. Still no idea...

Regards,
Michal