Re: [PATCH] mm, kmsan: fix infinite recursion due to RCU critical section

[Marco Elver]

On Thu, 18 Jan 2024 at 12:28, Charan Teja Kalla
<quic_charante@xxxxxxxxxxx> wrote:
>
> May I ask if KMSAN also instruments the access to the memory managed as
> ZONE_DEVICE. You know this is not the RAM and also these pages will
> never be onlined thus also not be available in buddy.
>
> Reason for the ask is that this patch is introduced because of a race
> between pfn walker ends up in pfn of zone device memory.
>
> If KMSAN never instruments this, does it look good to you to have the
> KMSAN version of pfn_valid(), as being suggested by Alexander in the
> other mail.

It would be nice to avoid duplicating functions - both options have downsides:
1. Shared pfn_valid(): it might break for KMSAN again in future if new
recursion is introduced.
2. KMSAN-version of pfn_valid(): it might break if pfn_valid() changes
in future.

I suspect #1 is less likely.

What is your main concern by switching to rcu_read_lock_sched()?