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

Dave Young
2017-03-08T07:05:22Z

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@amd.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