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SubjectRe: [tip: x86/urgent] x86/setup: Always reserve the first 1M of RAM
On Fri, Mar 3, 2023, at 1:10 AM, Mike Rapoport wrote:
> Hi Andy,
>
> On Wed, Mar 01, 2023 at 07:51:43PM -0800, Andy Lutomirski wrote:
>> On Thu, Jun 3, 2021, at 11:01 AM, tip-bot2 for Mike Rapoport wrote:
>> >
>> > x86/setup: Always reserve the first 1M of RAM
>> >
>
> ...
>
>> + /*
>> + * Unconditionally reserve the entire fisrt 1M, see comment in
>> + * setup_arch().
>> + */
>> + memblock_reserve(0, SZ_1M);
>>
>>
>> But this runs even if we just failed to allocate a trampoline on the
>> first try, again dooming the kernel to panic.
>>
>> 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.
>
> Currently, the second attempt to set_real_mode_mem() in
> efi_free_boot_services() does not allocate from memblock anyway but reuses
> memory freed from EFI services. Could be that failure to boot caused by
> another failing reservation?

I'm not actually sure what's wrong per se. Certainly efi=debug will utterly break my quirk, but other than that, I would have expected it to still work on a more careful reading.

Anyway, I have a fixup series that works in a VM that i'll test in a bit.

>
>> Discovered by my delightful laptop, which does not boot with this patch applied.
>
> Do you have early_printk() visible?

Yes, but I haven't found a smoking gun yet.

>
>> --Andy
>
> --
> Sincerely yours,
> Mike.

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