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    SubjectRe: [PATCH] x86, x86-64, gdt, hibernate: Store/load GDT for hibernate path.
    On Thu, May 02, 2013 at 02:34:38PM +0200, Pavel Machek wrote:
    > 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?

    Fortunatly not. The patch (7a5cd063c7b4c58417f674821d63f5eb6747e37) that
    just just landed in Linus a couple of days ago did change it a bit
    (as the 'saved_context' struct shrunk), but this patch brings it back
    to what it was before. But I don't know if the 'saved_context' structure
    is actually somewhere specifically mentioned as 'on-disk' or in the
    kernel.

    Looking at the code, I think the on-disk structure you are referring to
    is the 'struct restore_data_record' (please correct me if I am
    incorrect) which has not been affected by any of these patches.

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

    We certainly can. I can prep a patch to that affect on Friday or Monday.
    >
    > Pavel
    >
    > --
    > (english) http://www.livejournal.com/~pavelmachek
    > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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