linux-kernel - Re: [PATCH v2 2/2] memblock: do not start bottom-up allocations with kernel

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Message-Id: <20210122043714.266075-1-bauerman@linux.ibm.com>
Date:   Fri, 22 Jan 2021 01:37:14 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     rppt@...nel.org
Cc:     akpm@...ux-foundation.org, guro@...com, iamjoonsoo.kim@....com,
        Ram Pai <linuxram@...ibm.com>,
        Konrad Rzeszutek Wilk <konrad@...nok.org>,
        Satheesh Rajendran <sathnaga@...ux.vnet.ibm.com>,
        kernel-team@...com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        mhocko@...nel.org, riel@...riel.com,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Subject: Re: [PATCH v2 2/2] memblock: do not start bottom-up allocations with kernel_end

Mike Rapoport <rppt@...nel.org> writes:

> > Signed-off-by: Roman Gushchin <guro@...com>
> 
> Reviewed-by: Mike Rapoport <rppt@...ux.ibm.com>

I've seen a couple of spurious triggers of the WARN_ONCE() removed by this
patch. This happens on some ppc64le bare metal (powernv) server machines with
CONFIG_SWIOTLB=y and crashkernel=4G, as described in a candidate patch I posted
to solve this issue in a different way:

https://lore.kernel.org/linuxppc-dev/20201218062103.76102-1-bauerman@linux.ibm.com/

Since this patch solves that problem, is it possible to include it in the next
feasible v5.11-rcX, with the following tag?

Fixes: 8fabc623238e ("powerpc: Ensure that swiotlb buffer is allocated from low memory")

This is because reverting the commit above also solves the problem on the
machines where I've seen this issue.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center