linux-kernel - Re: [PATCH] sparc64: fix hugetlb for sun4u

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Message-ID: <7531c897d8a4dc874bc226f5cb724eb66ee17974.camel@physik.fu-berlin.de>
Date: Wed, 16 Jul 2025 08:18:46 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: Anthony Yznaga <anthony.yznaga@...cle.com>, sparclinux@...r.kernel.org, 
	davem@...emloft.net, andreas@...sler.com
Cc: linux-kernel@...r.kernel.org, agordeev@...ux.ibm.com, will@...nel.org, 
	ryan.roberts@....com, david@...hat.com, osalvador@...e.de
Subject: Re: [PATCH] sparc64: fix hugetlb for sun4u

Hi Anthony,

On Tue, 2025-07-15 at 18:24 -0700, Anthony Yznaga wrote:
> An attempt to exercise sparc hugetlb code in a sun4u-based guest
> running under qemu results in the guest hanging due to being stuck
> in a trap loop. This is due to invalid hugetlb TTEs being installed
> that do not have the expected _PAGE_PMD_HUGE and page size bits set.
> Although the breakage has gone apparently unnoticed for several years,
> fix it now so there is the option to exercise sparc hugetlb code under
> qemu. This can be useful because sun4v support in qemu does not support
> linux guests currently and sun4v-based hardware resources may not be
> readily available.

It has actually been observed for a long time that newer kernels are
unstable on sun4u while there are no stability issues on sun4v.

I'm not sure though whether the Debian kernel enables hugetlb by default.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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