Re: [PATCH] x86/hyperv/vtl: Stop kernel from probing VTL0 low memory

[Wei Liu]

On Fri, Jan 17, 2025 at 09:01:41AM -0800, Roman Kisel wrote:
> > For Linux, running in Hyper-V VTL (Virtual Trust Level), kernel in VTL2
> > tries to access VTL0 low memory in probe_roms. This memory is not
> > described in the e820 map. Initialize probe_roms call to no-ops
> > during boot for VTL2 kernel to avoid this. The issue got identified
> > in OpenVMM which detects invalid accesses initiated from kernel running
> > in VTL2.
> > 
> > Co-developed-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Naman Jain <namjain@xxxxxxxxxxxxxxxxxxx>
> > ---
> >  arch/x86/hyperv/hv_vtl.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
> > index 4e1b1e3b5658..3f4e20d7b724 100644
> > --- a/arch/x86/hyperv/hv_vtl.c
> > +++ b/arch/x86/hyperv/hv_vtl.c
> > @@ -30,6 +30,7 @@ void __init hv_vtl_init_platform(void)
> >	x86_platform.realmode_init = x86_init_noop;
> >	x86_init.irqs.pre_vector_init = x86_init_noop;
> >	x86_init.timers.timer_init = x86_init_noop;
> > +	x86_init.resources.probe_roms = x86_init_noop;
> >  
> >	/* Avoid searching for BIOS MP tables */
> >	x86_init.mpparse.find_mptable = x86_init_noop;
> > 
> > base-commit: 37136bf5c3a6f6b686d74f41837a6406bec6b7bc
> > -- 
> > 2.43.0
> 
> Thanks, Naman!
> 
> Tested-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>

Applied to hyperv-fixes. Thanks.