linux-kernel - Re: [PATCH] x86, x86-64, gdt, hibernate: Store/load GDT for hibernate path.

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Message-ID: <20130502123438.GD22618@amd.pavel.ucw.cz>
Date:	Thu, 2 May 2013 14:34:38 +0200
From:	Pavel Machek <pavel@....cz>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	rjw@...k.pl, tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org
Subject: Re: [PATCH] x86, x86-64, gdt, hibernate: Store/load GDT for
 hibernate path.

Hi!

> The git commite7a5cd063c7b4c58417f674821d63f5eb6747e37
> ("x86-64, gdt: Store/load GDT for ACPI S3 or hibernate/resume path
> is not needed.") assumes that for the hibernate path the booting
> kernel and the resuming kernel MUST be the same. That is certainly
> the case for a 32-bit kernel (see check_image_kernel and
> CONFIG_ARCH_HIBERNATION_HEADER config option).
> 
> However for 64-bit kernels it is OK to have a different kernel
> version (and size of the image) of the booting and resuming kernels.
> Hence the above mentioned git commit introduces an regression.

Ok.

> This patch fixes it by introducing a 'struct desc_ptr gdt_desc'
> back in the 'struct saved_context'. However instead of having in the
> 'save_processor_state' and 'restore_processor_state' the
> store/load_gdt calls, we are only saving the GDT in the
> save_processor_state.
> 
> For the restore path the lgdt operation is done in
> hibernate_asm_[32|64].S in the 'restore_registers' path.

So the on-disk format changed and we need to bump the version number
somewhere?

I guess we should add big fat warning to the affected structures.

								Pavel

-- 
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