Re: [Xen-devel] [PATCH v7 08/36] x86/mm: Add support to enable SME in early boot processing

[Tom Lendacky <thomas.lendacky@xxxxxxx>]

On 6/20/2017 2:38 AM, Borislav Petkov wrote:
> On Fri, Jun 16, 2017 at 01:51:15PM -0500, Tom Lendacky wrote:
> > Add support to the early boot code to use Secure Memory Encryption (SME).
> > Since the kernel has been loaded into memory in a decrypted state, encrypt
> > the kernel in place and update the early pagetables with the memory
> > encryption mask so that new pagetable entries will use memory encryption.
> >
> > The routines to set the encryption mask and perform the encryption are
> > stub routines for now with functionality to be added in a later patch.
> >
> > Because of the need to have the routines available to head_64.S, the
> > mem_encrypt.c is always built and #ifdefs in mem_encrypt.c will provide
> > functionality or stub routines depending on CONFIG_AMD_MEM_ENCRYPT.
> >
> > Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > ---
> >   arch/x86/include/asm/mem_encrypt.h |    8 +++++++
> >   arch/x86/kernel/head64.c           |   33 +++++++++++++++++++++---------
> >   arch/x86/kernel/head_64.S          |   39 ++++++++++++++++++++++++++++++++++--
> >   arch/x86/mm/Makefile               |    4 +---
> >   arch/x86/mm/mem_encrypt.c          |   24 ++++++++++++++++++++++
> >   5 files changed, 93 insertions(+), 15 deletions(-)
> ...
>
> > diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> > index b99d469..9a78277 100644
> > --- a/arch/x86/mm/mem_encrypt.c
> > +++ b/arch/x86/mm/mem_encrypt.c
> > @@ -11,6 +11,9 @@
> >    */
> >   
> >   #include <linux/linkage.h>
> > +#include <linux/init.h>
> > +
> > +#ifdef CONFIG_AMD_MEM_ENCRYPT
> >   
> >   /*
> >    * Since SME related variables are set early in the boot process they must
> > @@ -19,3 +22,24 @@
> >    */
> >   unsigned long sme_me_mask __section(.data) = 0;
> >   EXPORT_SYMBOL_GPL(sme_me_mask);
> > +
> > +void __init sme_encrypt_kernel(void)
> > +{
> > +}
> Just the minor:
>
> void __init sme_encrypt_kernel(void) { }
>
> in case you have to respin.
I have to re-spin for the kbuild test error.  But given that this
function will be filled in later it's probably not worth doing the
space savings here.

Thanks,
Tom

> Reviewed-by: Borislav Petkov <bp@xxxxxxx>
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