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From: Mike Rapoport <rppt@linux.ibm.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Michael Kelley <mikelley@microsoft.com>,
	James Morris <jmorris@namei.org>, Sasha Levin <sashal@kernel.org>,
	x86-ml <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>,
	James Morris <James.Morris@microsoft.com>
Subject: Re: [PATCH] x86/setup: Document that Windows reserves the first MiB
Date: Wed, 9 Jun 2021 11:54:39 +0300	[thread overview]
Message-ID: <YMCBz1ry0hKUyHgX@linux.ibm.com> (raw)
In-Reply-To: <YL/Tc1bGkgXKRKfT@zn.tnic>

On Tue, Jun 08, 2021 at 10:30:46PM +0200, Borislav Petkov wrote:
> It does so unconditionally too, on Intel and AMD machines, to work
> around BIOS bugs, as confirmed by Microsoft folks (see Link for full
> details).
> 
> Reflow the paragraph, while at it.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>

Acked-by: Mike Rapoport <rppt@linux.ibm.com>

Thanks for taking care of this!

> Link: https://lkml.kernel.org/r/MWHPR21MB159330952629D36EEDE706B3D7379@MWHPR21MB1593.namprd21.prod.outlook.com
> ---
>  arch/x86/kernel/setup.c | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 7638ac6c3d80..85acd22f8022 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1060,17 +1060,18 @@ void __init setup_arch(char **cmdline_p)
>  #endif
>  
>  	/*
> -	 * Find free memory for the real mode trampoline and place it
> -	 * there.
> -	 * If there is not enough free memory under 1M, on EFI-enabled
> -	 * systems there will be additional attempt to reclaim the memory
> -	 * for the real mode trampoline at efi_free_boot_services().
> +	 * Find free memory for the real mode trampoline and place it there. If
> +	 * there is not enough free memory under 1M, on EFI-enabled systems
> +	 * there will be additional attempt to reclaim the memory for the real
> +	 * mode trampoline at efi_free_boot_services().
>  	 *
> -	 * Unconditionally reserve the entire first 1M of RAM because
> -	 * BIOSes are know to corrupt low memory and several
> -	 * hundred kilobytes are not worth complex detection what memory gets
> -	 * clobbered. Moreover, on machines with SandyBridge graphics or in
> -	 * setups that use crashkernel the entire 1M is reserved anyway.
> +	 * Unconditionally reserve the entire first 1M of RAM because BIOSes
> +	 * are known to corrupt low memory and several hundred kilobytes are not
> +	 * worth complex detection what memory gets clobbered. Windows does the
> +	 * same thing for very similar reasons.
> +	 *
> +	 * Moreover, on machines with SandyBridge graphics or in setups that use
> +	 * crashkernel the entire 1M is reserved anyway.
>  	 */
>  	reserve_real_mode();
>  
> -- 
> 2.29.2
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette

-- 
Sincerely yours,
Mike.

  reply	other threads:[~2021-06-09  8:54 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-06  7:55 [GIT PULL] x86/urgent for v5.13-rc5 Borislav Petkov
2021-06-06 19:38 ` Linus Torvalds
2021-06-06 20:58   ` Mike Rapoport
2021-06-06 21:23     ` Linus Torvalds
2021-06-06 22:07       ` Borislav Petkov
2021-06-06 23:05         ` Sasha Levin
2021-06-07 18:46           ` James Morris
2021-06-08 17:53             ` Michael Kelley
2021-06-08 18:33               ` Borislav Petkov
2021-06-08 19:22                 ` Linus Torvalds
2021-06-08 20:01                   ` Borislav Petkov
2021-06-08 20:03                     ` Linus Torvalds
2021-06-08 20:30                       ` [PATCH] x86/setup: Document that Windows reserves the first MiB Borislav Petkov
2021-06-09  8:54                         ` Mike Rapoport [this message]
2021-06-06 20:14 ` [GIT PULL] x86/urgent for v5.13-rc5 pr-tracker-bot

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