Re: [PATCH] x86: Remove unnecessary kmap() from sgx_ioc_enclave_init()

[Christoph Hellwig]

On Fri, Jan 29, 2021 at 09:37:30AM -0800, Sean Christopherson wrote:
> On Thu, Jan 28, 2021, ira.weiny@xxxxxxxxx wrote:
> > From: Ira Weiny <ira.weiny@xxxxxxxxx>
> > 
> > There is no reason to alloc a page and kmap it to store this temporary
> > data from the user. 
> 
> Actually, there is, it's just poorly documented.  The sigstruct needs to be
> page aligned, and the token needs to be 512-byte aligned.  kmcalloc doesn't
> guarantee alignment.  IIRC things will work until slub_debug is enabled, at
> which point the natural alignment behavior goes out the window.

Well, there still is absolutely no need for the kmap as you can use
page_address for a GFP_KERNEL allocation.