linux-kernel - Re: [RFC v2-fix-v2 1/1] x86/boot: Add a trampoline for APs booting in 64-bit mode

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Date:   Fri, 21 May 2021 11:29:42 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2-fix-v2 1/1] x86/boot: Add a trampoline for APs booting in
 64-bit mode

On Fri, May 21, 2021 at 7:40 AM Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:
>
> From: Sean Christopherson <sean.j.christopherson@...el.com>
>
> Add a trampoline for booting APs in 64-bit mode via a software handoff
> with BIOS, and use the new trampoline for the ACPI MP wake protocol used
> by TDX. You can find MADT MP wake protocol details in ACPI specification
> r6.4, sec 5.2.12.19.
>
> Extend the real mode IDT pointer by four bytes to support LIDT in 64-bit
> mode.  For the GDT pointer, create a new entry as the existing storage
> for the pointer occupies the zero entry in the GDT itself.
>
> Reported-by: Kai Huang <kai.huang@...el.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---
>
> Changes since RFC v2-fix:
>  * Passed rmh as argument to get_trampoline_start_ip().
>  * Added a comment line for get_trampoline_start_ip().
>  * Moved X86_CR0_NE change from pa_trampoline_compat() to patch
>    "x86/boot: Avoid #VE during boot for TDX platforms".
>  * Fixed comments for tr_idt as per Dan's comments.
>  * Moved TRAMPOLINE_32BIT_CODE_SIZE change to "x86/boot: Avoid #VE
>    during boot for TDX platforms" patch.

Thanks, looks good, no more comments from me:

Reviewed-by: Dan Williams <dan.j.williams@...el.com>