Re: [PATCH -next] arch_topology: Fix cache attributes detection in the CPU hotplug path

From: Sudeep Holla
Date: Thu Jul 14 2022 - 12:00:24 EST

On Thu, Jul 14, 2022 at 03:27:09PM +0000, Conor.Dooley@xxxxxxxxxxxxx wrote:
> On 14/07/2022 16:01, Sudeep Holla wrote:
> >
> > Interesting, need to check if it is not in atomic context on arm64.
> > Wonder if some configs are disabled and making this bug hidden. Let me
> > check.
> >

OK, it turns I didn't have necessary config options enabled. Enabling
them, I did see the BUG splat and changing allocation to GFP_ATOMIC
fixed the same. Can you try that please so that you can test if other
things are fine.

> > One possible solution is to add GFP_ATOMIC to the allocation but I want
> > to make sure if it is legal to be in atomic context when calling
> > update_siblings_masks.
> >

So I take is as legal and needs to be fixed to push my patch.

> >>>
> >>> Anyways give this a try, also test the CPU hotplug and check if nothing
> >>> is broken on RISC-V. We noticed this bug only on one platform while
> >>
> >> So, our system monitor that runs openSBI does not actually support
> >> any hotplug features yet, so:
> >
> > OK, we can ignore hotplug on RISC-V for now then. We have tested on multiple
> > arm64 platforms(DT as well as ACPI).
> >
> Well, other vendors implementations of firmware-come-bootloaders-
> running-openSBI may support it, but (currently) ours does not.
> But, if no-one else is speaking up about this, my arch-topo changes
> or your original patchset...