Re: [PATCH 2/2] x86/cpu: clear SME/SEV/SEV_ES features when not in use

[Limonciello, Mario]

On 2/11/2022 02:31, Borislav Petkov wrote:
> On Thu, Feb 10, 2022 at 11:36:52PM -0600, Mario Limonciello wrote:
> > Currently SME/SEV/SEV_ES features are reflective of whether the CPU
> > supports the features but not whether they have been activated by the
> > kernel.
> >
> > Change this around to clear the features if the kernel is not using
> > them so userspace can determine if they are available and in use
> > from `/proc/cpuinfo`.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> >   arch/x86/kernel/cpu/amd.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> > index 4edb6f0f628c..4a7d4801fa0b 100644
> > --- a/arch/x86/kernel/cpu/amd.c
> > +++ b/arch/x86/kernel/cpu/amd.c
> > @@ -611,12 +611,20 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
> >   		if (!(msr & MSR_K7_HWCR_SMMLOCK))
> >   			goto clear_sev;
> >   
> > +		if (!cc_platform_has(CC_ATTR_MEM_ENCRYPT))
> > +			goto clear_all;
> > +		if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
> > +			goto clear_sev;
> > +		if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
> > +			goto clear_sev_es;
>
> The cc_platform stuff is to be used in generic code - I think you can
> safely read MSR_AMD64_SEV here and look at the bits, just like the rest
> of this code does.

Yeah I was just looking to avoid the code duplication in multiple parts 
of the kernel.  If it's preferable to just duplicate the logic that 
cc_platform_has here for the AMD platform, I'll do that instead.

> Also, why is this a separate patch? I.e., one single patch should be
> just fine.

Very well, will squash them.