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Message-ID: <0b1ebda7-cf70-47bc-9d31-129eb895ae9f@kernel.org>
Date: Mon, 4 Mar 2024 12:28:23 +0530
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Subject: Re: [PATCH] powerpc: align memory_limit to 16MB in early_parse_mem
To: Michael Ellerman <mpe@ellerman.id.au>, Joel Savitz <jsavitz@redhat.com>,
 linux-kernel@vger.kernel.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
 Christophe Leroy <christophe.leroy@csgroup.eu>,
 "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
 Benjamin Gray <bgray@linux.ibm.com>, Paul Mackerras <paulus@ozlabs.org>,
 linuxppc-dev@lists.ozlabs.org, Gonzalo Siero <gsierohu@redhat.com>
References: <20240301203023.2197451-1-jsavitz@redhat.com>
 <87cysdfsef.fsf@mail.lhotse>
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From: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
In-Reply-To: <87cysdfsef.fsf@mail.lhotse>
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On 3/2/24 4:53 AM, Michael Ellerman wrote:
> Hi Joel,
> 
> Joel Savitz <jsavitz@redhat.com> writes:
>> On 64-bit powerpc, usage of a non-16MB-aligned value for the mem= kernel
>> cmdline parameter results in a system hang at boot.
> 
> Can you give us any more details on that? It might be a bug we can fix.
> 
>> For example, using 'mem=4198400K' will always reproduce this issue.
>>
>> This patch fixes the problem by aligning any argument to mem= to 16MB
>> corresponding with the large page size on powerpc.
> 
> The large page size depends on the MMU, with Radix it's 2MB or 1GB. So
> depending on what's happening 16MB may not be enough.
> 
> What system are you testing on?
> 

htab_bolt_mapping should have aligned things to a lower value that is 16MB aligned.

	/* Carefully map only the possible range */
	vaddr = ALIGN(vstart, step);
	paddr = ALIGN(pstart, step);
	vend  = ALIGN_DOWN(vend, step);


-aneesh