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

[Dave Young]

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@xxxxxxx>
> ---
>  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