linux-kernel - Re: [PATCH v8 01/40] x86/compressed/64: detect/setup SEV/SME features earlier in boot

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Date:   Wed, 15 Dec 2021 11:51:48 -0600
From:   Michael Roth <michael.roth@....com>
To:     Venu Busireddy <venu.busireddy@...cle.com>
CC:     Borislav Petkov <bp@...en8.de>,
        Brijesh Singh <brijesh.singh@....com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        <linux-efi@...r.kernel.org>, <platform-driver-x86@...r.kernel.org>,
        <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "Vitaly Kuznetsov" <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        "Andy Lutomirski" <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        <tony.luck@...el.com>, <marcorr@...gle.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: Re: [PATCH v8 01/40] x86/compressed/64: detect/setup SEV/SME
 features earlier in boot

On Tue, Dec 14, 2021 at 06:14:34PM -0600, Venu Busireddy wrote:
> On 2021-12-14 20:10:16 +0100, Borislav Petkov wrote:
> > On Tue, Dec 14, 2021 at 11:46:14AM -0600, Venu Busireddy wrote:
> > > What I am suggesting should not have anything to do with the boot stage
> > > of the kernel.
> > 
> > I know exactly what you're suggesting.
> > 
> > > For example, both these functions call native_cpuid(), which is declared
> > > as an inline function. I am merely suggesting to do something similar
> > > to avoid the code duplication.
> > 
> > Try it yourself. If you can come up with something halfway readable and
> > it builds, I'm willing to take a look.
> 
> Patch (to be applied on top of sev-snp-v8 branch of
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FAMDESE%2Flinux.git&amp;data=04%7C01%7Cmichael.roth%40amd.com%7Cbff83ee03b1147c39ea808d9bf5fe9d8%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637751240979543818%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=DZpgEtthswLhhfWqZlLkHHd5nJW2jb%2FVFuTssAFJ6Uo%3D&amp;reserved=0) is attached at the end.
> 
> Here are a few things I did.
> 
> 1. Moved all the common code that existed at the begining of
>    sme_enable() and sev_enable() to an inline function named
>    get_pagetable_bit_pos().
> 2. sme_enable() was using AMD_SME_BIT and AMD_SEV_BIT, whereas
>    sev_enable() was dealing with raw bits. Moved those definitions to
>    sev.h, and changed sev_enable() to use those definitions.
> 3. Make consistent use of BIT_ULL.

Hi Venu,

I know there's still comments floating around, but once there's consensus feel
free to respond with a separate precursor patch against tip which moves
sme_enable() cpuid code into your helper function, along with your S-o-B, and I
can include it directly in the next version. Otherwise, I can incorporate your
suggestions into the next spin, just let me know if it's okay to add:

  Co-authored-by: Venu Busireddy <venu.busireddy@...cle.com>
  Signed-off-by:  Venu Busireddy <venu.busireddy@...cle.com>

to the relevant commits.

Thank you (and Boris/Tom) for the suggestions!

-Mike

> 
> Venu
>