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From:   Saurabh Singh Sengar <ssengar@microsoft.com>
To:     Wei Liu <wei.liu@kernel.org>,
        Saurabh Sengar <ssengar@linux.microsoft.com>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
CC:     KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Dexuan Cui <decui@microsoft.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
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        "Michael Kelley (LINUX)" <mikelley@microsoft.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "hpa@zytor.com" <hpa@zytor.com>
Subject: RE: [EXTERNAL] Re: [PATCH v3] x86/hyperv: add noop functions to
 x86_init mpparse functions
Thread-Topic: [EXTERNAL] Re: [PATCH v3] x86/hyperv: add noop functions to
 x86_init mpparse functions
Thread-Index: AQHZqeo2WlZ5UIAxR0aDcrQ0GzS+4a/EUOGA
Date:   Fri, 21 Jul 2023 12:58:01 +0000
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References: <1687537688-5397-1-git-send-email-ssengar@linux.microsoft.com>
 <ZJx02GzzoQ9E1TH9@liuwe-devbox-debian-v2>
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> -----Original Message-----
> From: Wei Liu <wei.liu@kernel.org>
> Sent: Wednesday, June 28, 2023 11:29 PM
> To: Saurabh Sengar <ssengar@linux.microsoft.com>
> Cc: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang
> <haiyangz@microsoft.com>; wei.liu@kernel.org; Dexuan Cui
> <decui@microsoft.com>; tglx@linutronix.de; mingo@redhat.com;
> bp@alien8.de; dave.hansen@linux.intel.com; x86@kernel.org; Michael Kelley
> (LINUX) <mikelley@microsoft.com>; linux-kernel@vger.kernel.org; linux-
> hyperv@vger.kernel.org; hpa@zytor.com
> Subject: [EXTERNAL] Re: [PATCH v3] x86/hyperv: add noop functions to
> x86_init mpparse functions
>=20
> On Fri, Jun 23, 2023 at 09:28:08AM -0700, Saurabh Sengar wrote:
> > Hyper-V can run VMs at different privilege "levels" known as Virtual
> > Trust Levels (VTL). Sometimes, it chooses to run two different VMs at
> > different levels but they share some of their address space. In such
> > setups VTL2 (higher level VM) has visibility of all of the
> > VTL0 (level 0) memory space.
> >
> > When the CONFIG_X86_MPPARSE is enabled for VTL2, the VTL2 kernel
> > performs a search within the low memory to locate MP tables. However,
> > in systems where VTL0 manages the low memory and may contain valid
> > tables, this scanning can result in incorrect MP table information
> > being provided to the VTL2 kernel, mistakenly considering VTL0's MP
> > table as its own
> >
> > Add noop functions to avoid MP parse scan by VTL2.
> >
> > Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
>=20
> Hi Dave, are you happy with the commit message?

HI Dave,

If there is no concern, can I get your ack

- Saurabh

>=20
> > ---
> > [V3]
> >  - modify commit message.
> >
> >  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
> > 85d38b9f3586..db5d2ea39fc0 100644
> > --- a/arch/x86/hyperv/hv_vtl.c
> > +++ b/arch/x86/hyperv/hv_vtl.c
> > @@ -25,6 +25,10 @@ void __init hv_vtl_init_platform(void)
> >  	x86_init.irqs.pre_vector_init =3D x86_init_noop;
> >  	x86_init.timers.timer_init =3D x86_init_noop;
> >
> > +	/* Avoid searching for BIOS MP tables */
> > +	x86_init.mpparse.find_smp_config =3D x86_init_noop;
> > +	x86_init.mpparse.get_smp_config =3D x86_init_uint_noop;
> > +
> >  	x86_platform.get_wallclock =3D get_rtc_noop;
> >  	x86_platform.set_wallclock =3D set_rtc_noop;
> >  	x86_platform.get_nmi_reason =3D hv_get_nmi_reason;
> > --
> > 2.34.1
> >