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Date:   Mon, 16 Apr 2018 11:40:07 +0200
From:   Ingo Molnar <mingo@kernel.org>
To:     Laura Abbott <labbott@redhat.com>
Cc:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
        kernel-hardening@lists.openwall.com
Subject: Re: [PATCH] x86/xen: Remove use of VLAs
Message-ID: <20180416094007.diuobump2qxraybx@gmail.com>
References: <20180413221146.28476-1-labbott@redhat.com>
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* Laura Abbott <labbott@redhat.com> wrote:

> There's an ongoing effort to remove VLAs[1] from the kernel to eventually
> turn on -Wvla. The few VLAs in use have an upper bound based on a size
> of 64K. This doesn't produce an excessively large stack so just switch
> the upper bound.
> 
> [1] https://lkml.org/lkml/2018/3/7/621
> 
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
>  arch/x86/xen/enlighten_pv.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> index c36d23aa6c35..d96a5a535cbb 100644
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -421,8 +421,7 @@ static void xen_load_gdt(const struct desc_ptr *dtr)
>  {
>  	unsigned long va = dtr->address;
>  	unsigned int size = dtr->size + 1;
> -	unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE);
> -	unsigned long frames[pages];
> +	unsigned long frames[DIV_ROUND_UP(SZ_64K, PAGE_SIZE)];
>  	int f;
>  
>  	/*
> @@ -470,8 +469,7 @@ static void __init xen_load_gdt_boot(const struct desc_ptr *dtr)
>  {
>  	unsigned long va = dtr->address;
>  	unsigned int size = dtr->size + 1;
> -	unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE);
> -	unsigned long frames[pages];
> +	unsigned long frames[DIV_ROUND_UP(SZ_64K, PAGE_SIZE)];
>  	int f;

Reviewed-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo