linux-kernel - Re: [PATCHv6 20/30] x86/boot: Add a trampoline for booting APs via firmware handoff

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Date:   Thu, 17 Mar 2022 23:21:55 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Boris Petkov <bp@...en8.de>
Cc:     tglx@...utronix.de, dave.hansen@...el.com, mingo@...hat.com,
        luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        brijesh.singh@....com, ak@...ux.intel.com, david@...hat.com,
        dan.j.williams@...el.com, wanpengli@...cent.com, jgross@...e.com,
        linux-kernel@...r.kernel.org, hpa@...or.com, jmattson@...gle.com,
        pbonzini@...hat.com, seanjc@...gle.com, jpoimboe@...hat.com,
        vkuznets@...hat.com, joro@...tes.org, thomas.lendacky@....com,
        sdeep@...are.com, x86@...nel.org, knsathya@...nel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        tony.luck@...el.com
Subject: Re: [PATCHv6 20/30] x86/boot: Add a trampoline for booting APs via
 firmware handoff

On Thu, Mar 17, 2022 at 12:44:42PM +0000, Boris Petkov wrote:
> On March 16, 2022 2:08:46 AM UTC, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote:
> >diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> >index 48067af94678..35006e151774 100644
> >--- a/arch/x86/include/asm/apic.h
> >+++ b/arch/x86/include/asm/apic.h
> >@@ -328,6 +328,8 @@ struct apic {
> > 
> > 	/* wakeup_secondary_cpu */
> > 	int	(*wakeup_secondary_cpu)(int apicid, unsigned long start_eip);
> >+	/* wakeup secondary CPU using 64-bit wakeup point */
> >+	int	(*wakeup_secondary_cpu_64)(int apicid, unsigned long start_eip);
> > 
> > 	void	(*inquire_remote_apic)(int apicid);
> > 
> >diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
> >index 331474b150f1..fd6f6e5b755a 100644
> >--- a/arch/x86/include/asm/realmode.h
> >+++ b/arch/x86/include/asm/realmode.h
> >@@ -25,6 +25,7 @@ struct real_mode_header {
> > 	u32	sev_es_trampoline_start;
> > #endif
> > #ifdef CONFIG_X86_64
> >+	u32	trampoline_start64;
> 
> I had already asked about those here: why do you need to add a new u32 here and can't use trampoline_start?
> 
> Ditto for the new function pointer too.
> 
> And yes, sev_es_trampoline_start is superfluous too.

As I said[1], I'm confused by the request. These field initialized at
build time. I don't see how a single field would work.

[1] https://lore.kernel.org/all/20220216141009.ymmjduf5doqnhnqy@black.fi.intel.com/

-- 
 Kirill A. Shutemov