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Date:   Tue, 12 May 2020 15:17:23 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Qian Cai <cai@lca.pw>
Cc:     Michael Ellerman <mpe@ellerman.id.au>, paulus@ozlabs.org,
        benh@kernel.crashing.org, kvm-ppc@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/kvm: silence kmemleak false positives
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References: <87y2pybu38.fsf@mpe.ellerman.id.au>
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On Mon, May 11, 2020 at 07:43:30AM -0400, Qian Cai wrote:
> On May 11, 2020, at 7:15 AM, Michael Ellerman <mpe@ellerman.id.au> wrote:
> > There is kmemleak_alloc_phys(), which according to the docs can be used
> > for tracking a phys address.
> > 
> > Did you try that?
> 
> Catalin, feel free to give your thoughts here.
> 
> My understanding is that it seems the doc is a bit misleading.
> kmemleak_alloc_phys() is to allocate kmemleak objects for a physical
> address range, so  kmemleak could scan those memory pointers within
> for possible referencing other memory. It was only used in memblock so
> far, but those new memory allocations here contain no reference to
> other memory.
> 
> In this case, we have already had kmemleak objects for those memory
> allocation. It is just that other pointers reference those memory by
> their physical address which is a known kmemleak limitation won’t be
> able to track the the connection. Thus, we always use
> kmemleak_ignore() to not reporting those as leaks and don’t scan those
> because they do not contain other memory reference.

Indeed. I replied directly to Michael along the same lines.

-- 
Catalin