From: Matt Fleming <matt@codeblueprint.co.uk>
To: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Mario Limonciello <mario_limonciello@dell.com>,
Matthew Garrett <mjg59@srcf.ucam.org>,
Borislav Petkov <bp@alien8.de>, Matt Fleming <mfleming@suse.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4.8? 0/4] Allow the trampoline to use EFI boot services RAM
Date: Sun, 31 Jul 2016 22:38:17 +0100 [thread overview]
Message-ID: <20160731213817.GC3636@codeblueprint.co.uk> (raw)
In-Reply-To: <cover.1469573005.git.luto@kernel.org>
On Tue, 26 Jul, at 03:55:24PM, Andy Lutomirski wrote:
> As currently configured, my laptop cannot boot any existing kernel
> because the real mode trampoline can't be reserved. The ranges in
> which it could live are rejected by the kernel: one is EFI boot
> services data and the other is above the EBDA.
>
> Allowing use of RAM between the EBDA and 640k is scary: there are
> probably many quirky BIOSes out there, and, as currently structured,
> it would be awkward to allow it just on EFI boots because we
> currently reserve that range before we figure out whether we're
> using EFI.
>
> This series fixes it the other way: it allow the trampoline to live
> in boot services memory. It achieves this by deferring the panic
> due to failure to reserve a trampoline until early_initcall time
> and then adjusting the EFI boot services quirk to reserve space
> for the trampoline if we haven't already found it a home.
>
> I'm hoping this is okay for 4.8 even though it's late: it fixes
> a boot failure and it's fairly conservative -- the only significant
> changes in behavior should be on systems that currently fail to boot.
>
> I'm not currently proposing it for stable because AFAIK I'm the
> only person to have seen this issue. If it survives in Linus'
> tree for a while, though, I might propose it for -stable later
> on.
I took a very, very quick look over this series and nothing jumped out
as being wrong. I'll take a much closer look this week.
next prev parent reply other threads:[~2016-07-31 21:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-26 22:55 [PATCH 4.8? 0/4] Allow the trampoline to use EFI boot services RAM Andy Lutomirski
2016-07-26 22:55 ` [PATCH 1/4] x86/boot: Synchronize trampoline_cr4_features and mmu_cr4_features directly Andy Lutomirski
2016-07-26 22:55 ` [PATCH 2/4] x86/boot: Defer setup_real_mode() to early_initcall time Andy Lutomirski
2016-07-26 22:55 ` [PATCH 3/4] x86/boot: Rework reserve_real_mode() to allow multiple tries Andy Lutomirski
2016-07-26 22:55 ` [PATCH 4/4] x86/efi: Allocate a trampoline if needed in efi_free_boot_services() Andy Lutomirski
2016-08-01 5:07 ` H. Peter Anvin
2016-08-02 18:21 ` Andy Lutomirski
2016-07-31 21:38 ` Matt Fleming [this message]
2016-08-04 9:26 ` [PATCH 4.8? 0/4] Allow the trampoline to use EFI boot services RAM Matt Fleming
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