linux-kernel - Re: [RFC v2 28/32] x86/tdx: Make pages shared in ioremap()

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Date:   Mon, 10 May 2021 22:52:49 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [RFC v2 28/32] x86/tdx: Make pages shared in ioremap()

+Boris, who has similar opinions on sev_active().

On Mon, May 10, 2021, Dave Hansen wrote:
> On 5/10/21 3:23 PM, Kuppuswamy, Sathyanarayanan wrote:
> >>>>
> >>>> -    if (!sev_active())
> >>>> +    if (!sev_active() && !is_tdx_guest())
> >>>>           return 0;
> >>> I think it's time to come up with a real name for all of the code that's
> >>> under: (sev_active() || is_tdx_guest()).
> >>>
> >>> "encrypted" isn't it, for sure.
> >>
> >> I called it protected_guest() in some other patches.
> > 
> > If you are also fine with above mentioned function name, I can include it
> > in this series. Since we have many use cases of above condition, it will
> > be useful define it as helper function.
> 
> FWIW, I think sev_active() has a horrible name.  Shouldn't that be
> "is_sev_guest()"?  "sev_active()" could be read as "I'm a SEV host" or
> "I'm a SEV guest" and "SEV is active".

I can't find the thread offhand, but Boris proposed something along the lines of
cpu_has(), but specific to a given flavor of protected guest.  IIRC, it was
sev_guest_has(SEV_ES) or something like that.

I 100% agree that we should have actual feature bits somewhere for the various
protected guest flavors.

> protected_guest() seems fine to cover both, despite the horrid SEV
> naming.  It'll actually be nice to banish it from appearing in many of
> its uses. :)