linux-kernel - Re: [RFC PATCH 6/6] x86/x2apic-savic: Not set APIC backing page if Secure AVIC is not enabled.

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Message-ID: <CAMvTesA4A+ErFf+RoDJGrHVfkXOTgeZ0qw_5CRT47UbLJ-2Z0g@mail.gmail.com>
Date: Fri, 16 May 2025 23:58:21 +0800
From: Tianyu Lan <ltykernel@...il.com>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org, 
	decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, 
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, 
	yuehaibing@...wei.com, jacob.jun.pan@...ux.intel.com, jpoimboe@...nel.org, 
	tiala@...rosoft.com, linux-hyperv@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 6/6] x86/x2apic-savic: Not set APIC backing page if
 Secure AVIC is not enabled.

On Wed, May 7, 2025 at 12:03 PM Neeraj Upadhyay <Neeraj.Upadhyay@....com> wrote:
>
>
>
> On 5/6/2025 6:37 PM, Tianyu Lan wrote:
> > From: Tianyu Lan <tiala@...rosoft.com>
> >
> > When Secure AVIC is not enabled, init_apic_page()
> > should return directly.
> >
> > Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> > ---
> >  arch/x86/kernel/apic/x2apic_savic.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/x86/kernel/apic/x2apic_savic.c b/arch/x86/kernel/apic/x2apic_savic.c
> > index 0dd7e39931b0..fb09c0f9e276 100644
> > --- a/arch/x86/kernel/apic/x2apic_savic.c
> > +++ b/arch/x86/kernel/apic/x2apic_savic.c
> > @@ -333,6 +333,9 @@ static void init_apic_page(void)
> >  {
> >       u32 apic_id;
> >
> > +     if (!cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
> > +             return;
> > +
> >       /*
>
> Why is this change needed? init_apic_page() is only called from Secure AVIC driver's
> setup() callback. savic_probe() already does this check. So, if this check fails during
> savic_probe(), Secure AVIC apic driver won't be selected as apic driver and it's setup
> callback will never get invoked.
>
>
Hi Neeraj:
       Thanks for your review. Agree. Will remove it.


--
Thanks
Tianyu Lan