Messages in this thread | | | Date | Thu, 2 Mar 2023 16:22:16 +0100 | From | Borislav Petkov <> | Subject | Re: [tip: x86/urgent] x86/setup: Always reserve the first 1M of RAM |
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On Thu, Mar 02, 2023 at 07:06:11AM -0800, Andy Lutomirski wrote: > There is no possible way that Windoze genuinely reserves the first 1M. > It does SMP, and x86 needs <1M memory for SMP, so Windoze uses <1M > memory. QED :)
Then we need to sort this out first. Because this patch says the contrary.
> >> I real the commit message and the linked bug, and I'm having trouble > >> finding evidence of anything actually fixed by this patch. Can we > >> just revert it? If not, it would be nice to get a fixup patch that > >> genuinely cleans this up -- the whole structure of the code (first, > >> try to allocate trampoline, then free boot services, then try again) > >> isn't really conducive to a model where we *don't* free boot services > >> < 1M. > > > > Yes, I think this makes most sense. And that whole area is a minefield > > so the less we upset the current universe, the better. > > I'll send a revert patch.
I actually replied to the text which spoke about a "fixup patch" - not a revert patch.
> Thinking about this a bit more, if we actually want to "reserve" <1M, > we should implement it completely differently by treating <1M as its > very own special thing and teaching the memblock allocator to refuse > to allocate <1M unless specifically requested. There's only a very > small number of allocations that need it (crashkernel for some > reason?), and there are at least two spurious users of > memblock_phys_alloc_range that curently may use <1M but have no > business doing so (ramdisk code and the NUMA distance table). But > let's only do that if there's an actual problem to solve.
No, look at early_reserve_memory(). All kinds of crap use that <1M and we do special reservations there.
I agree with making it a special region aspect.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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