linux-kernel - Re: [PATCH v3] powerpc/lockdep: fix a false positive warning

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Date:   Wed, 11 Sep 2019 00:14:34 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Qian Cai <cai@....pw>
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mingo@...nel.org,
        peterz@...radead.org, bvanassche@....org, arnd@...db.de,
        kvm-ppc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: Re: [PATCH v3] powerpc/lockdep: fix a false positive warning

Hi Qian,

Sorry I haven't replied sooner, I've been travelling.

Qian Cai <cai@....pw> writes:
> The commit 108c14858b9e ("locking/lockdep: Add support for dynamic
> keys") introduced a boot warning on powerpc below, because since the
> commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds
> kvm_tmp[] into the .bss section and then free the rest of unused spaces
> back to the page allocator.

Thanks for debugging this, but I'd like to fix it differently.

kvm_tmp has caused trouble before, with kmemleak, and it can also cause
trouble with STRICT_KERNEL_RWX, so I'd like to change how it's done,
rather than doing more hacks for it.

It should just be a page in text that we use if needed, and don't free,
which should avoid all these problems.

I'll try and get that done and posted soon.

cheers