linux-kernel - Re: [PATCHv7 02/30] x86/tdx: Provide common base for SEAMCALL and TDCALL C wrappers

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Date:   Sat, 19 Mar 2022 15:48:11 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...el.com,
        luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        thomas.lendacky@....com, brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCHv7 02/30] x86/tdx: Provide common base for SEAMCALL and
 TDCALL C wrappers

On Fri, Mar 18, 2022 at 06:30:20PM +0300, Kirill A. Shutemov wrote:
> Secure Arbitration Mode (SEAM) is an extension of VMX architecture.  It
> defines a new VMX root operation (SEAM VMX root) and a new VMX non-root
> operation (SEAM VMX non-root) which are both isolated from the legacy
> VMX operation where the host kernel runs.
> 
> A CPU-attested software module (called 'TDX module') runs in SEAM VMX
> root to manage and protect VMs running in SEAM VMX non-root.  SEAM VMX
> root is also used to host another CPU-attested software module (called
> 'P-SEAMLDR') to load and update the TDX module.
> 
> Host kernel transits to either P-SEAMLDR or TDX module via the new
> SEAMCALL instruction, which is essentially a VMExit from VMX root mode
> to SEAM VMX root mode.  SEAMCALLs are leaf functions defined by
> P-SEAMLDR and TDX module around the new SEAMCALL instruction.
> 
> A guest kernel can also communicate with TDX module via TDCALL
> instruction.
> 
> TDCALLs and SEAMCALLs use an ABI different from the x86-64 system-v ABI.
> RAX is used to carry both the SEAMCALL leaf function number (input) and
> the completion status (output).  Additional GPRs (RCX, RDX, R8-R11) may
> be further used as both input and output operands in individual leaf.
> 
> TDCALL and SEAMCALL share the same ABI and require the largely same
> code to pass down arguments and retrieve results.
> 
> Define an assembly macro that can be used to implement C wrapper for
> both TDCALL and SEAMCALL.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> TDCALL wrapper will be implemented using the macro later in the series.
> SEAMCALL wrapper is out-of-scope for the series and will be implemented
> as part of TDX host enabling.
> ---
>  arch/x86/include/asm/tdx.h      | 28 ++++++++++
>  arch/x86/kernel/asm-offsets.c   |  9 ++++
>  arch/x86/virt/vmx/tdx/tdxcall.S | 94 +++++++++++++++++++++++++++++++++
>  3 files changed, 131 insertions(+)
>  create mode 100644 arch/x86/virt/vmx/tdx/tdxcall.S

Instead of hurrying to send the set again two days after the v6 one -

  [ I frankly wonder why you're even in such a hurry - it seems people
    believe that hammering out the patches constantly would somehow get them
    upstreamed faster :-\ ]

- you should rather apply more diligence and take care of working in all
the comments from last review:

https://lore.kernel.org/r/87lex9321l.ffs@tglx

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette