linux-kernel - Re: [PATCHv6 03/30] x86/tdx: Add __tdx_module_call() and __tdx

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Message-ID: <YjNb2bTrlA4LyZKH@zn.tnic>
Date:   Thu, 17 Mar 2022 17:03:37 +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: [PATCHv6 03/30] x86/tdx: Add __tdx_module_call() and
 __tdx_hypercall() helper functions

On Wed, Mar 16, 2022 at 05:08:29AM +0300, Kirill A. Shutemov wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> 
> Guests communicate with VMMs with hypercalls. Historically, these
> are implemented using instructions that are known to cause VMEXITs
> like VMCALL, VMLAUNCH, etc. However, with TDX, VMEXITs no longer
> expose the guest state to the host. This prevents the old hypercall
> mechanisms from working. So, to communicate with VMM, TDX
> specification defines a new instruction called TDCALL.

...

> For registers used by the TDCALL instruction, please check TDX GHCI
> specification, the section titled "TDCALL instruction" and "TDG.VP.VMCALL
> Interface".
> 
> Based on previous patch by Sean Christopherson.
> 
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>
> ---
>  arch/x86/coco/tdx/Makefile    |   2 +-
>  arch/x86/coco/tdx/tdcall.S    | 191 ++++++++++++++++++++++++++++++++++
>  arch/x86/coco/tdx/tdx.c       |  23 ++++
>  arch/x86/include/asm/tdx.h    |  27 +++++
>  arch/x86/kernel/asm-offsets.c |   8 ++
>  5 files changed, 250 insertions(+), 1 deletion(-)
>  create mode 100644 arch/x86/coco/tdx/tdcall.S

With tglx's comment fixed:

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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