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From:   Thiago Jung Bauermann <bauerman@linux.ibm.com>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>, riel@surriel.com,
        kernel-team@fb.com, Ram Pai <linuxram@us.ibm.com>,
        linux-kernel@vger.kernel.org, mhocko@kernel.org,
        linux-mm@kvack.org,
        Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>,
        Konrad Rzeszutek Wilk <konrad@darnok.org>,
        iamjoonsoo.kim@lge.com, guro@fb.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 2/2] memblock: do not start bottom-up allocations
 with kernel_end
In-reply-to: <20210124073421.GG6332@kernel.org>
Date:   Mon, 08 Feb 2021 20:58:07 -0300
Message-ID: <87ft26yuwg.fsf@manicouagan.localdomain>
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Mike Rapoport <rppt@kernel.org> writes:

> On Sat, Jan 23, 2021 at 06:09:11PM -0800, Andrew Morton wrote:
>> On Fri, 22 Jan 2021 01:37:14 -0300 Thiago Jung Bauermann <bauerman@linux.ibm.com> wrote:
>> 
>> > Mike Rapoport <rppt@kernel.org> writes:
>> > 
>> > > > Signed-off-by: Roman Gushchin <guro@fb.com>
>> > > 
>> > > Reviewed-by: Mike Rapoport <rppt@linux.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?
>> 
>> We could do this, if we're confident that this patch doesn't depend on
>> [1/2] "mm: cma: allocate cma areas bottom-up"?  I think it is...
>
> A think it does not depend on cma bottom-up allocation, it's rather the other
> way around: without this CMA bottom-up allocation could fail with KASLR
> enabled.

I noticed that this patch is now upstream as:

2dcb39645441 memblock: do not start bottom-up allocations with kernel_end

> Still, this patch may need updates to the way x86 does early reservations:
>
> https://lore.kernel.org/lkml/20210115083255.12744-1-rppt@kernel.org

... but the patches from this link still aren't. Isn't this a potential
problem for x86?

The patch series on the link above is now superseded by v2:

https://lore.kernel.org/linux-mm/20210128105711.10428-1-rppt@kernel.org/

-- 
Thiago Jung Bauermann
IBM Linux Technology Center