linux-kernel - Re: [RFC PATCH v4 24/28] x86: Access the setup data through debugfs decrypted

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Date:   Wed, 8 Mar 2017 15:04:59 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Larry Woodman <lwoodman@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v4 24/28] x86: Access the setup data through debugfs
 decrypted

On 02/16/17 at 09:47am, Tom Lendacky wrote:
> Use memremap() to map the setup data.  This simplifies the code and will
> make the appropriate decision as to whether a RAM remapping can be done
> or if a fallback to ioremap_cache() is needed (which includes checking
> PageHighMem).
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/kernel/kdebugfs.c |   30 +++++++++++-------------------
>  1 file changed, 11 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/kernel/kdebugfs.c b/arch/x86/kernel/kdebugfs.c
> index bdb83e4..c3d354d 100644
> --- a/arch/x86/kernel/kdebugfs.c
> +++ b/arch/x86/kernel/kdebugfs.c
> @@ -48,17 +48,13 @@ static ssize_t setup_data_read(struct file *file, char __user *user_buf,
>  
>  	pa = node->paddr + sizeof(struct setup_data) + pos;
>  	pg = pfn_to_page((pa + count - 1) >> PAGE_SHIFT);
> -	if (PageHighMem(pg)) {
> -		p = ioremap_cache(pa, count);
> -		if (!p)
> -			return -ENXIO;
> -	} else
> -		p = __va(pa);
> +	p = memremap(pa, count, MEMREMAP_WB);
> +	if (!p)
> +		return -ENXIO;

-ENOMEM looks better for memremap, ditto for other places..

>  
>  	remain = copy_to_user(user_buf, p, count);
>  
> -	if (PageHighMem(pg))
> -		iounmap(p);
> +	memunmap(p);
>  
>  	if (remain)
>  		return -EFAULT;
> @@ -127,15 +123,12 @@ static int __init create_setup_data_nodes(struct dentry *parent)
>  		}
>  
>  		pg = pfn_to_page((pa_data+sizeof(*data)-1) >> PAGE_SHIFT);
> -		if (PageHighMem(pg)) {
> -			data = ioremap_cache(pa_data, sizeof(*data));
> -			if (!data) {
> -				kfree(node);
> -				error = -ENXIO;
> -				goto err_dir;
> -			}
> -		} else
> -			data = __va(pa_data);
> +		data = memremap(pa_data, sizeof(*data), MEMREMAP_WB);
> +		if (!data) {
> +			kfree(node);
> +			error = -ENXIO;
> +			goto err_dir;
> +		}
>  
>  		node->paddr = pa_data;
>  		node->type = data->type;
> @@ -143,8 +136,7 @@ static int __init create_setup_data_nodes(struct dentry *parent)
>  		error = create_setup_data_node(d, no, node);
>  		pa_data = data->next;
>  
> -		if (PageHighMem(pg))
> -			iounmap(data);
> +		memunmap(data);
>  		if (error)
>  			goto err_dir;
>  		no++;
> 

Thanks
Dave