linux-kernel - Re: [PATCH v2] x86/setup: call early_reserve

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Date:   Tue, 21 Sep 2021 02:01:28 +0200
From:   Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, efault@....de,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] x86/setup: call early_reserve_memory() earlier

On Mon, Sep 20, 2021 at 02:04:21PM +0200, Juergen Gross wrote:
> Commit a799c2bd29d19c565 ("x86/setup: Consolidate early memory
> reservations") introduced early_reserve_memory() to do all needed
> initial memblock_reserve() calls in one function. Unfortunately the
> call of early_reserve_memory() is done too late for Xen dom0, as in
> some cases a Xen hook called by e820__memory_setup() will need those
> memory reservations to have happened already.
> 
> Move the call of early_reserve_memory() before the call of
> e820__memory_setup() in order to avoid such problems.
> 
> Cc: stable@...r.kernel.org
> Fixes: a799c2bd29d19c565 ("x86/setup: Consolidate early memory reservations")
> Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
> Signed-off-by: Juergen Gross <jgross@...e.com>

I confirm this fixes my boot issue too.

Tested-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>

> ---
> V2:
> - update comment (Jan Beulich, Boris Petkov)
> - move call down in setup_arch() (Mike Galbraith)
> ---
>  arch/x86/kernel/setup.c | 26 ++++++++++++++------------
>  1 file changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 79f164141116..40ed44ead063 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -830,6 +830,20 @@ void __init setup_arch(char **cmdline_p)
>  
>  	x86_init.oem.arch_setup();
>  
> +	/*
> +	 * Do some memory reservations *before* memory is added to memblock, so
> +	 * memblock allocations won't overwrite it.
> +	 *
> +	 * After this point, everything still needed from the boot loader or
> +	 * firmware or kernel text should be early reserved or marked not RAM in
> +	 * e820. All other memory is free game.
> +	 *
> +	 * This call needs to happen before e820__memory_setup() which calls the
> +	 * xen_memory_setup() on Xen dom0 which relies on the fact that those
> +	 * early reservations have happened already.
> +	 */
> +	early_reserve_memory();
> +
>  	iomem_resource.end = (1ULL << boot_cpu_data.x86_phys_bits) - 1;
>  	e820__memory_setup();
>  	parse_setup_data();
> @@ -876,18 +890,6 @@ void __init setup_arch(char **cmdline_p)
>  
>  	parse_early_param();
>  
> -	/*
> -	 * Do some memory reservations *before* memory is added to
> -	 * memblock, so memblock allocations won't overwrite it.
> -	 * Do it after early param, so we could get (unlikely) panic from
> -	 * serial.
> -	 *
> -	 * After this point everything still needed from the boot loader or
> -	 * firmware or kernel text should be early reserved or marked not
> -	 * RAM in e820. All other memory is free game.
> -	 */
> -	early_reserve_memory();
> -
>  #ifdef CONFIG_MEMORY_HOTPLUG
>  	/*
>  	 * Memory used by the kernel cannot be hot-removed because Linux
> -- 
> 2.26.2
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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