RE: [EXTERNAL] Re: [PATCH v3] x86/hyperv: add noop functions to x86_init mpparse functions

[Saurabh Singh Sengar]

> -----Original Message-----
> From: Wei Liu <wei.liu@xxxxxxxxxx>
> Sent: Wednesday, June 28, 2023 11:29 PM
> To: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
> Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; wei.liu@xxxxxxxxxx; Dexuan Cui
> <decui@xxxxxxxxxxxxx>; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx;
> bp@xxxxxxxxx; dave.hansen@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; Michael Kelley
> (LINUX) <mikelley@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-
> hyperv@xxxxxxxxxxxxxxx; hpa@xxxxxxxxx
> Subject: [EXTERNAL] Re: [PATCH v3] x86/hyperv: add noop functions to
> x86_init mpparse functions
> 
> 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@xxxxxxxxxxxxxxxxxxx>
> 
> Hi Dave, are you happy with the commit message?

HI Dave,

If there is no concern, can I get your ack

- Saurabh

> 
> > ---
> > [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 = 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;
> > +
> >  	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
> >