On Thu, 2025-02-13 at 15:24 +0100, Greg Kroah-Hartman wrote:
> 6.13-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> [ Upstream commit 4b5bc2ec9a239bce261ffeafdd63571134102323 ]
>
> Now that the following fix:
>
> d0ceea662d45 ("x86/mm: Add _PAGE_NOPTISHADOW bit to avoid updating userspace page tables")
>
> stops kernel_ident_mapping_init() from scribbling over the end of a
> 4KiB PGD by assuming the following 4KiB will be a userspace PGD,
> there's no good reason for the kexec PGD to be part of a single
> 8KiB allocation with the control_code_page.
>
> ( It's not clear that that was the reason for x86_64 kexec doing it that
> way in the first place either; there were no comments to that effect and
> it seems to have been the case even before PTI came along. It looks like
> it was just a happy accident which prevented memory corruption on kexec. )
>
> Either way, it definitely isn't needed now. Just allocate the PGD
> separately on x86_64, like i386 already does.
No objection (which is just as well given how late I am in replying)
but I'm just not sure *why*. This doesn't fix a real bug; it's just a
cleanup.
Does this mean I should have written my original commit message better,
to make it clearer that this *isn't* a bugfix?
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