linux-kernel - Re: [GIT PULL] x86/boot changes for v6.10

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Date: Mon, 13 May 2024 18:02:57 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, "the arch/x86 maintainers" <x86@...nel.org>, 
	Ard Biesheuvel <ardb@...nel.org>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [GIT PULL] x86/boot changes for v6.10

On Sun, 12 May 2024 at 23:51, Ingo Molnar <mingo@...nel.org> wrote:
>
>  - Re-introduce a bootloader quirk wrt. CR4 handling

I've pulled this, but shouldn't the compressed boot also just stop
setting the G flag that it didn't understand?

For example, arch/x86/kernel/head64.c seems to do this:

        pmd_entry = __PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL;

but arch/x86/boot/compressed/ident_map_64.c does the somewhat suspect

        mapping_info.page_flag = __PAGE_KERNEL_LARGE_EXEC | sme_me_mask;

without masking off _PAGE_GLOBAL.

The hibernation code does

        pgprot_t pmd_text_prot = __pgprot(__PAGE_KERNEL_LARGE_EXEC);
        pgprot_val(pmd_text_prot) &= __default_kernel_pte_mask;

and again there are several situations where __default_kernel_pte_mask
does not have _PAGE_GLOBAL.

So again, the boot/compressed code seems a bit at an odds with other
code paths. The cr4 games seem to work around the fact that this code
is just buggy.

Hmm?

          Linus