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

[Tom Lendacky]

On 7/28/2017 3:47 AM, David Laight wrote:
> 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@xxxxxxx>
> > >
> > > 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@xxxxxxx>
> > > Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> > > ---
> > >   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.

The function would check a single variable/memory location and making it
an inline function would accomplish that.

Thanks,
Tom

> 	David