linux-kernel - Re: [PATCH] powerpc/xive: Fix some incorrect memory allocation

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Date:   Sat, 25 Jun 2022 13:29:35 +0200
From:   Cédric Le Goater <clg@...d.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
CC:     <linux-kernel@...r.kernel.org>, <kernel-janitors@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] powerpc/xive: Fix some incorrect memory allocation

Hello Christophe,

On 6/25/22 11:49, Christophe JAILLET wrote:
> 'xibm->count' really looks like a number of bits (see how it is used in
> __xive_irq_bitmap_alloc()), so use the bitmap API to allocate and free this
> bitmap.
> 
> This improves semantic and potentially avoids some over memory allocation.

This is correct and
  
> Fixes: eac1e731b59e ("powerpc/xive: guest exploitation of the XIVE interrupt controller")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> I don't cross compile, so this patch is NOT compile-tested.


Nathan provided a fix for it already :

  http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220623182509.3985625-1-nathanl@linux.ibm.com/

Thanks,

C.

> ---
>   arch/powerpc/sysdev/xive/spapr.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/sysdev/xive/spapr.c b/arch/powerpc/sysdev/xive/spapr.c
> index 7d5128676e83..fdbebb14b7de 100644
> --- a/arch/powerpc/sysdev/xive/spapr.c
> +++ b/arch/powerpc/sysdev/xive/spapr.c
> @@ -57,7 +57,7 @@ static int __init xive_irq_bitmap_add(int base, int count)
>   	spin_lock_init(&xibm->lock);
>   	xibm->base = base;
>   	xibm->count = count;
> -	xibm->bitmap = kzalloc(xibm->count, GFP_KERNEL);
> +	xibm->bitmap = bitmap_zalloc(xibm->count, GFP_KERNEL);
>   	if (!xibm->bitmap) {
>   		kfree(xibm);
>   		return -ENOMEM;
> @@ -75,7 +75,7 @@ static void xive_irq_bitmap_remove_all(void)
>   
>   	list_for_each_entry_safe(xibm, tmp, &xive_irq_bitmaps, list) {
>   		list_del(&xibm->list);
> -		kfree(xibm->bitmap);
> +		bitmap_free(xibm->bitmap);
>   		kfree(xibm);
>   	}
>   }