RE: [RFC Part1 PATCH v3 07/17] x86/mm: Include SEV for encryption memory attribute changes

David Laight
2017-07-28T08:47:30Z

From: Borislav Petkov
> Sent: 27 July 2017 15:59
> On Mon, Jul 24, 2017 at 02:07:47PM -0500, Brijesh Singh wrote:
> > From: Tom Lendacky <thomas.lendacky@amd.com>
> >
> > The current code checks only for sme_active() when determining whether
> > to perform the encryption attribute change. Include sev_active() in this
> > check so that memory attribute changes can occur under SME and SEV.
> >
> > Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> > ---
> > arch/x86/mm/pageattr.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
> > index dfb7d65..b726b23 100644
> > --- a/arch/x86/mm/pageattr.c
> > +++ b/arch/x86/mm/pageattr.c
> > @@ -1781,8 +1781,8 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
> > unsigned long start;
> > int ret;
> >
> > - /* Nothing to do if the SME is not active */
> > - if (!sme_active())
> > + /* Nothing to do if SME and SEV are not active */
> > + if (!sme_active() && !sev_active())
>
> This is the second place which does
>
> if (!SME && !SEV)
>
> I wonder if, instead of sprinking those, we should have a
>
> if (mem_enc_active())
>
> or so which unifies all those memory encryption logic tests and makes
> the code more straightforward for readers who don't have to pay
> attention to SME vs SEV ...

If any of the code paths are 'hot' it would make sense to be checking
a single memory location.

David