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From: Anup Patel <anup@brainfault.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Damien Le Moal <Damien.LeMoal@wdc.com>,
	Palmer Dabbelt <palmer@sifive.com>,
	Anup Patel <anup.patel@wdc.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Atish Patra <atish.patra@wdc.com>,
	linux-riscv@lists.infradead.org
Subject: Re: 32bit kernel is broken for Linux-5.1-rc1 due to GCC cmodel=medlow
Date: Fri, 22 Mar 2019 19:07:29 +0530	[thread overview]
Message-ID: <CAAhSdy1VS8-3npcZUzjicnKGsjHcc6WH3Co6Hx2=GvttoatWcA@mail.gmail.com> (raw)
In-Reply-To: <20190322132556.GB19263@infradead.org>

On Fri, Mar 22, 2019 at 6:55 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Fri, Mar 22, 2019 at 12:42:10PM +0200, Mike Rapoport wrote:
> > Hi,
> >
> > On Fri, Mar 22, 2019 at 11:46:24AM +0530, Anup Patel wrote:
> > > Hi Palmer,
> > >
> > > The 32bit kernel booting is broken for Linux-5.1-rc1 due to GCC cmodel=medlow
> > > affecting setup_vm() movement from kernel/setup.c to mm/init.c.
> > >
> > > There is no issue with 64bit kernel booting.
> > >
> > > The "[PATCH v2 2/5] RISC-V: Make setup_vm() independent of GCC code model"
> > > fixes this issue.
> > >
> > > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1959102.html
> > >
> > > If possible please include above patch as Linux-5.1-rc1 fix.
> >
> > I'm not convinced that it's the best solution. Multiple __load_pa() and
> > __load_va() conversions make code unreadable.
> > Is there any reason swapper_pg_dir cannot be setup after 'relocate'? It'll
> > save a lot of churn for the current fix and for the addition of 4K mappings
>
> I think for 5.1-rc we should just revert the cleanup patch ASAP until
> we figure out what else we want to do.

I think reverting is not right way to go here because there is deeper issue
in using GCC cmodel=medlow with setup_vm() which is called from assembly
with MMU off.

Even if we keep setup_vm() in kernel/setup.c then still in-future it can break
for 32bit system as more code gets added to kernel/setup.c.

The setup_vm() should not be sensitive to which source file it is placed in.
The patch which breaks 32bit kernel just moves setup_vm() from
kernel/setup.c to mm/init.c.

Regards,
Anup

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  reply	other threads:[~2019-03-22 13:37 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-22  6:16 32bit kernel is broken for Linux-5.1-rc1 due to GCC cmodel=medlow Anup Patel
2019-03-22 10:42 ` Mike Rapoport
2019-03-22 12:29   ` Anup Patel
2019-03-22 13:26     ` Christoph Hellwig
2019-03-22 13:38       ` Anup Patel
2019-03-22 13:25   ` Christoph Hellwig
2019-03-22 13:37     ` Anup Patel [this message]
2019-03-22 13:40       ` Christoph Hellwig
2019-03-22 13:45         ` Anup Patel
2019-03-23 17:21           ` Christoph Hellwig
2019-03-24  1:42             ` Anup Patel
2019-03-24  1:56               ` Gary Guo
2019-03-24  3:04                 ` Anup Patel
2019-03-24  3:10                 ` Anup Patel
2019-03-24  6:05                   ` Mike Rapoport
2019-03-24  9:41                     ` Anup Patel
2019-03-24  8:37               ` Christoph Hellwig

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