linux-kernel - Re: [PATCH RFC 1/7] x86/head/64: Mark startup_gdt and startup_gdt_descr as _

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Date:   Mon, 16 Oct 2023 13:57:06 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Hou Wenlong <houwenlong.hwl@...group.com>
Cc:     linux-kernel@...r.kernel.org,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mike Rapoport <rppt@...nel.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>
Subject: Re: [PATCH RFC 1/7] x86/head/64: Mark startup_gdt and
 startup_gdt_descr as __initdata


* Hou Wenlong <houwenlong.hwl@...group.com> wrote:

> As startup_gdt and startup_gdt_descr are only used in booting, make them
> as __initdata to allow them to be freed after boot.
> 
> Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
> ---
>  arch/x86/kernel/head64.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 49f7629b17f7..dd357807ffb5 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -69,7 +69,7 @@ EXPORT_SYMBOL(vmemmap_base);
>  /*
>   * GDT used on the boot CPU before switching to virtual addresses.
>   */
> -static struct desc_struct startup_gdt[GDT_ENTRIES] = {
> +static struct desc_struct startup_gdt[GDT_ENTRIES] __initdata = {
>  	[GDT_ENTRY_KERNEL32_CS]         = GDT_ENTRY_INIT(0xc09b, 0, 0xfffff),
>  	[GDT_ENTRY_KERNEL_CS]           = GDT_ENTRY_INIT(0xa09b, 0, 0xfffff),
>  	[GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(0xc093, 0, 0xfffff),
> @@ -79,7 +79,7 @@ static struct desc_struct startup_gdt[GDT_ENTRIES] = {
>   * Address needs to be set at runtime because it references the startup_gdt
>   * while the kernel still uses a direct mapping.
>   */
> -static struct desc_ptr startup_gdt_descr = {
> +static struct desc_ptr startup_gdt_descr __initdata = {
>  	.size = sizeof(startup_gdt),
>  	.address = 0,

Yeah, so I think this and patch #1 are independently useful of the PIE 
feature, and I merged them into tip:x86/boot for a v6.7 merge.

Mind re-sending any other patches for x86 that can be merged? For example 
patch #6 looks good too, but was mixed up a bit with a previous 
PIE-enablement patch. Moving the __head definition to a header should also 
probably done as a separate patch, followed by the widening of its use.

Thanks,

	Ingo