linux-kernel - Re: [PATCH v9 04/18] x86/apic: Initialize APIC ID for Secure AVIC

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Message-ID: <20250819215304.GMaKTyQBWi6YzqZ0bW@fat_crate.local>
Date: Tue, 19 Aug 2025 23:53:04 +0200
From: Borislav Petkov <bp@...en8.de>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	dave.hansen@...ux.intel.com, Thomas.Lendacky@....com,
	nikunj@....com, Santosh.Shukla@....com, Vasant.Hegde@....com,
	Suravee.Suthikulpanit@....com, David.Kaplan@....com, x86@...nel.org,
	hpa@...or.com, peterz@...radead.org, seanjc@...gle.com,
	pbonzini@...hat.com, kvm@...r.kernel.org,
	kirill.shutemov@...ux.intel.com, huibo.wang@....com,
	naveen.rao@....com, francescolavra.fl@...il.com,
	tiala@...rosoft.com
Subject: Re: [PATCH v9 04/18] x86/apic: Initialize APIC ID for Secure AVIC

On Mon, Aug 11, 2025 at 03:14:30PM +0530, Neeraj Upadhyay wrote:
> Initialize the APIC ID in the Secure AVIC APIC backing page with
> the APIC_ID msr value read from Hypervisor. CPU topology evaluation
> later during boot would catch and report any duplicate APIC ID for
> two CPUs.
> 
> Reviewed-by: Tianyu Lan <tiala@...rosoft.com>
> Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
> ---
> Changes since v8:
>  - Added Tianyu's Reviewed-by.
>  - Code cleanup.
> 
>  arch/x86/kernel/apic/x2apic_savic.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/kernel/apic/x2apic_savic.c b/arch/x86/kernel/apic/x2apic_savic.c
> index 86a522685230..55edc6c30ba4 100644
> --- a/arch/x86/kernel/apic/x2apic_savic.c
> +++ b/arch/x86/kernel/apic/x2apic_savic.c
> @@ -141,6 +141,12 @@ static void savic_setup(void)
>  	enum es_result res;
>  	unsigned long gpa;
>  
> +	/*
> +	 * Before Secure AVIC is enabled, APIC msr reads are intercepted.

s/msr/MSR/g

Please check your whole text for such acronyms.

> +	 * APIC_ID msr read returns the value from the Hypervisor.
> +	 */
> +	apic_set_reg(ap, APIC_ID, native_apic_msr_read(APIC_ID));
> +
>  	gpa = __pa(ap);
>  
>  	/*
> -- 
> 2.34.1
> 

-- 
Regards/Gruss,
    Boris.

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