From: "H. Peter Anvin" <hpa@zytor.com>
To: "Ahmed S. Darwish" <darwish.07@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, X86-ML <x86@kernel.org>,
Tony Luck <tony.luck@intel.com>, Dave Jones <davej@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Randy Dunlap <rdunlap@xenotime.net>,
Willy Tarreau <wtarreau@hera.kernel.org>,
Willy Tarreau <w@1wt.eu>, Dirk Hohndel <hohndel@infradead.org>,
Dirk.Hohndel@intel.com,
Simon Kagstrom <simon.kagstrom@netinsight.net>,
IDE-ML <linux-ide@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -next 2/2][RFC] x86: Saveoops: Reserve low memory and register code
Date: Tue, 25 Jan 2011 09:29:58 -0800 [thread overview]
Message-ID: <4D3F0896.4050006@zytor.com> (raw)
In-Reply-To: <20110125135326.GC10051@laptop>
On 01/25/2011 05:53 AM, Ahmed S. Darwish wrote:
> +
> +/*
> + * Extended BIOS services write to disk in units of 512-byte sectors.
> + * Thus, always align the ring buffer size on a 512-byte boundary.
> + */
Units of sectors, not always 512 bytes. This needs to be done
correctly, or you will destroy real data.
> +/*
> + * Page tables to identity map the first 2 Mbytes.
> + */
> +static __aligned(PAGE_SIZE) pud_t ident_level3[PTRS_PER_PUD];
> +static __aligned(PAGE_SIZE) pmd_t ident_level2[PTRS_PER_PMD];
> +
> +/*
> + * The lmode->rmode switching code needs to run from an identity page
> + * since it disables paging.
> + */
> +static void build_identity_mappings(void)
> +{
> + pgd_t *pgde;
> + pud_t *pude;
> + pmd_t *pmde;
> +
> + pmde = ident_level2;
> + set_pmd(pmde, __pmd(0 + __PAGE_KERNEL_IDENT_LARGE_EXEC));
> +
> + pude = ident_level3;
> + set_pud(pude, __pud(__pa(ident_level2) + _KERNPG_TABLE));
> +
> + pgde = init_level4_pgt;
> + set_pgd(pgde, __pgd(__pa(ident_level3) + _KERNPG_TABLE));
> +
> + __flush_tlb_all();
> +}
We now have a permanent identity map so there is no point in building a
new one.
However, I'm quite nervous about this -- this patch has *plenty* of real
possibility of wrecking data.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2011-01-25 17:32 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-25 13:47 [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon panic Ahmed S. Darwish
2011-01-25 13:51 ` [PATCH -next 1/2][RFC] x86: Saveoops: Switch to real-mode and call BIOS Ahmed S. Darwish
2011-01-25 17:26 ` H. Peter Anvin
2011-01-25 13:53 ` [PATCH -next 2/2][RFC] x86: Saveoops: Reserve low memory and register code Ahmed S. Darwish
2011-01-25 17:29 ` H. Peter Anvin [this message]
2011-01-26 9:04 ` Ahmed S. Darwish
2011-01-25 14:09 ` [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon panic Ingo Molnar
2011-01-25 15:08 ` Tejun Heo
2011-01-25 17:33 ` H. Peter Anvin
2011-01-26 11:44 ` Ahmed S. Darwish
2011-02-03 14:36 ` Pavel Machek
2011-02-03 15:28 ` H. Peter Anvin
2011-02-03 17:57 ` Ingo Molnar
2011-02-03 21:07 ` H. Peter Anvin
2011-01-25 15:36 ` Ahmed S. Darwish
2011-01-25 16:02 ` James Bottomley
2011-01-25 17:05 ` Ahmed S. Darwish
2011-01-25 17:20 ` James Bottomley
2011-01-25 22:10 ` Mark Lord
2011-01-25 22:16 ` Randy Dunlap
2011-01-25 22:45 ` Jeff Garzik
2011-01-25 22:58 ` H. Peter Anvin
2011-01-26 0:26 ` Jeff Garzik
2011-01-31 2:59 ` Rusty Russell
2011-01-31 10:45 ` Ingo Molnar
2011-01-25 17:32 ` Tony Luck
2011-01-25 17:36 ` H. Peter Anvin
2011-01-25 19:04 ` Jeff Garzik
2011-01-25 14:49 ` Tejun Heo
2011-01-28 7:59 ` Jan Ceuleers
2011-01-25 20:25 ` Linus Torvalds
[not found] ` <20110126124954.GC24527@laptop>
2011-01-26 23:07 ` Luck, Tony
[not found] ` <20110126231620.GA14807@redhat.com>
[not found] ` <987664A83D2D224EAE907B061CE93D53019438EB02@orsmsx505.amr.corp.intel.com>
[not found] ` <20110126233033.GB14807@redhat.com>
[not found] ` <987664A83D2D224EAE907B061CE93D53019438EBB6@orsmsx505.amr.corp.intel.com>
[not found] ` <4D40F7F1.3020509@zytor.com>
[not found] ` <20110127120039.GD20279@elte.hu>
2011-01-27 18:35 ` Luck, Tony
[not found] ` <4D4197CB.9070201@zytor.com>
[not found] ` <20110127162429.GB26437@elte.hu>
2011-01-27 18:56 ` Luck, Tony
[not found] ` <20110127021338.GA20334@redhat.com>
[not found] ` <4D40F81E.1030009@zytor.com>
[not found] ` <20110127052639.GA16289@laptop>
[not found] ` <m1sjweyeax.fsf@fess.ebiederm.org>
2011-02-02 11:13 ` Ahmed S. Darwish
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