From: Paul Burton <paul.burton@mips.com>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
James Hogan <jhogan@kernel.org>,
Mike Rapoport <rppt@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Thomas Bogendoerfer <tbogendoerfer@suse.de>,
Huacai Chen <chenhc@lemote.com>, Stefan Agner <stefan@agner.ch>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Juergen Gross <jgross@suse.com>,
"linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 04/12] mips: Reserve memory for the kernel image resources
Date: Tue, 30 Apr 2019 22:58:33 +0000 [thread overview]
Message-ID: <20190430225832.cjk7mj6dotw3cib6@pburton-laptop> (raw)
In-Reply-To: <20190426000035.yfonfvrapmm4j3fg@mobilestation>
Hi Serge,
On Fri, Apr 26, 2019 at 03:00:36AM +0300, Serge Semin wrote:
> > 1) Older systems generally had something like an ISA bus which used
> > addresses below the kernel, and bootloaders like YAMON left behind
> > functions that could be called right at the start of RAM. This sort
> > of thing should be accounted for by /memreserve/ in DT or similar
> > platform-specific reservations though rather than generically, and
> > at least Malta & SEAD-3 DTs already have /memreserve/ entries for
> > it. So this part I think is OK. Some other older platforms might
> > need updating, but that's fine.
> >
>
> Regarding ISA. As far as I remember devices on that bus can DMA only to the
> lowest 16MB. So in case if kernel is too big or placed pretty much high,
> they may be left even without reachable memory at all in current
> implementation.
Sure - I'm not too worried about these old buses, platforms can continue
to reserve the memory through DT or otherwise if they need to.
> > 2) trap_init() only allocates memory for the exception vector if using
> > a vectored interrupt mode. In other cases it just uses CAC_BASE
> > which currently gets reserved as part of this region between
> > PHYS_OFFSET & _text.
> >
> > I think this behavior is bogus, and we should instead:
> >
> > - Allocate the exception vector memory using memblock_alloc() for
> > CPUs implementing MIPSr2 or higher (ie. CPUs with a programmable
> > EBase register). If we're not using vectored interrupts then
> > allocating one page will do, and we already have the size
> > calculation for if we are.
> >
> > - Otherwise use CAC_BASE but call memblock_reserve() on the first
> > page.
> >
> > I think we should make that change before this one goes in. I can
> > try to get to it tomorrow, but feel free to beat me to it.
> >
>
> As far as I understood you and the code this should be enough to fix
> the problem:
> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
> index 98ca55d62201..f680253e2617 100644
> --- a/arch/mips/kernel/traps.c
> +++ b/arch/mips/kernel/traps.c
> @@ -2326,6 +2326,8 @@ void __init trap_init(void)
> ebase += (read_c0_ebase() & 0x3ffff000);
> }
> }
> +
> + memblock_reserve(ebase, PAGE_SIZE);
> }
>
> if (cpu_has_mmips) {
> ---
>
> Allocation has already been implemented in the if-branch under the
> (cpu_has_veic || cpu_has_vint) condition. So we don't need to change
> there anything.
> In case if vectored interrupts aren't supported the else-clause is
> taken and we need to reserve whatever is set in the exception base
> address variable.
>
> I'll add this patch between 3d and 4th ones if you are ok with it.
I think that would work, but I have other motivations to allocate the
memory in non-vectored cases anyway. I just sent a series that does that
& cleans up a little [1]. If you could take a look that would be great.
With that change made I think this patch will be good to apply.
Thanks,
Paul
[1] https://lore.kernel.org/linux-mips/20190430225216.7164-1-paul.burton@mips.com/T/#t
next prev parent reply other threads:[~2019-04-30 22:58 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 22:47 [PATCH 00/12] mips: Post-bootmem-memblock transition fixes Serge Semin
2019-04-23 22:47 ` [PATCH 01/12] mips: Make sure kernel .bss exists in boot mem pool Serge Semin
2019-04-24 22:30 ` Paul Burton
2019-04-23 22:47 ` [PATCH 02/12] mips: Discard rudiments from bootmem_init Serge Semin
2019-04-24 22:30 ` Paul Burton
2019-04-23 22:47 ` [PATCH 03/12] mips: Combine memblock init and memory reservation loops Serge Semin
2019-04-24 22:30 ` Paul Burton
2019-04-23 22:47 ` [PATCH 04/12] mips: Reserve memory for the kernel image resources Serge Semin
2019-04-24 22:43 ` Paul Burton
2019-04-26 0:00 ` Serge Semin
2019-04-30 22:58 ` Paul Burton [this message]
2019-05-02 14:24 ` Serge Semin
2019-05-02 18:45 ` Paul Burton
2019-05-03 17:21 ` Serge Semin
2019-05-02 18:35 ` Paul Burton
2019-05-21 14:56 ` Geert Uytterhoeven
2019-05-21 15:53 ` Mike Rapoport
2019-05-21 16:39 ` Serge Semin
2019-05-22 7:50 ` Geert Uytterhoeven
2019-05-22 7:47 ` Geert Uytterhoeven
2019-05-22 8:08 ` Mike Rapoport
2019-05-22 8:14 ` Geert Uytterhoeven
2019-05-22 13:34 ` Serge Semin
2019-05-22 13:44 ` Geert Uytterhoeven
2019-05-22 13:54 ` Serge Semin
2020-10-14 9:49 ` Maciej W. Rozycki
2019-04-23 22:47 ` [PATCH 05/12] mips: Discard post-CMA-init foreach loop Serge Semin
2019-05-02 18:35 ` Paul Burton
2019-04-23 22:47 ` [PATCH 06/12] mips: Use memblock to reserve the __nosave memory range Serge Semin
2019-05-02 18:35 ` Paul Burton
2019-04-23 22:47 ` [PATCH 07/12] mips: Add reserve-nomap memory type support Serge Semin
2019-05-02 18:35 ` Paul Burton
2019-04-23 22:47 ` [PATCH 08/12] mips: Dump memblock regions for debugging Serge Semin
2019-04-24 13:45 ` Mike Rapoport
2019-04-24 14:20 ` Serge Semin
2019-04-23 22:47 ` [PATCH 09/12] mips: Perform early low memory test Serge Semin
2019-04-23 22:47 ` [PATCH 10/12] mips: Print the kernel virtual mem layout on debugging Serge Semin
2019-04-24 13:47 ` Mike Rapoport
2019-04-24 14:35 ` Serge Semin
2019-04-23 22:47 ` [PATCH 11/12] mips: Make sure dt memory regions are valid Serge Semin
2019-04-23 22:47 ` [PATCH 12/12] mips: Enable OF_RESERVED_MEM config Serge Semin
2019-04-24 6:17 ` Christoph Hellwig
2019-04-24 8:34 ` Serge Semin
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