linux-kernel - RE: [EXTERNAL] Re: [PATCH] x86/hyperv: add noop functions to x86

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Message-ID: <PUZP153MB0749D15A769E61181593C6FABE4EA@PUZP153MB0749.APCP153.PROD.OUTLOOK.COM>
Date:   Fri, 2 Jun 2023 16:27:25 +0000
From:   Saurabh Singh Sengar <ssengar@...rosoft.com>
To:     Wei Liu <wei.liu@...nel.org>,
        Saurabh Sengar <ssengar@...ux.microsoft.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "hpa@...or.com" <hpa@...or.com>
Subject: RE: [EXTERNAL] Re: [PATCH] x86/hyperv: add noop functions to x86_init
 mpparse functions



> -----Original Message-----
> From: Wei Liu <wei.liu@...nel.org>
> Sent: Friday, June 2, 2023 9:53 PM
> To: Saurabh Sengar <ssengar@...ux.microsoft.com>
> Cc: KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; wei.liu@...nel.org; Dexuan Cui
> <decui@...rosoft.com>; tglx@...utronix.de; mingo@...hat.com;
> bp@...en8.de; dave.hansen@...ux.intel.com; x86@...nel.org; Michael Kelley
> (LINUX) <mikelley@...rosoft.com>; linux-kernel@...r.kernel.org; linux-
> hyperv@...r.kernel.org; hpa@...or.com
> Subject: [EXTERNAL] Re: [PATCH] x86/hyperv: add noop functions to x86_init
> mpparse functions
> 
> On Fri, Jun 02, 2023 at 05:41:52AM -0700, Saurabh Sengar wrote:
> > In !ACPI system, there is no way to disable CONFIG_X86_MPPARSE.
> > When CONFIG_X86_MPPARSE is enabled for VTL2, the kernel will scan low
> > memory looking for MP tables. Don't allow this, because low memory is
> > controlled by VTL0 and may contain actual valid tables for VTL0, which
> > can confuse the VTL2 kernel.
> >
> > Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
> > ---
> >  arch/x86/hyperv/hv_vtl.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c index
> > 1ba5d3b99b16..ea21d897b5da 100644
> > --- a/arch/x86/hyperv/hv_vtl.c
> > +++ b/arch/x86/hyperv/hv_vtl.c
> > @@ -23,6 +23,10 @@ void __init hv_vtl_init_platform(void)
> >  	x86_init.irqs.pre_vector_init = x86_init_noop;
> >  	x86_init.timers.timer_init = x86_init_noop;
> >
> > +	/* Avoid searching for BIOS MP tables */
> > +	x86_init.mpparse.find_smp_config = x86_init_noop;
> > +	x86_init.mpparse.get_smp_config = x86_init_uint_noop;
> > +
> 
> The code looks fine.
> 
> Can you expand the commit message a bit so that people who are not
> familiar with VTL and your setup can understand what's going on?

Sure, I will add more details in commit message.

> 
> Thanks,
> Wei.
> 
> >  	x86_platform.get_wallclock = get_rtc_noop;
> >  	x86_platform.set_wallclock = set_rtc_noop;
> >  	x86_platform.get_nmi_reason = hv_get_nmi_reason;
> > --
> > 2.34.1
> >