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

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Message-ID: <Z6wEuas8LbRVoBP_@liuwe-devbox-debian-v2>
Date: Wed, 12 Feb 2025 02:17:29 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Roman Kisel <romank@...ux.microsoft.com>
Cc: namjain@...ux.microsoft.com, bp@...en8.de, dave.hansen@...ux.intel.com,
	decui@...rosoft.com, haiyangz@...rosoft.com, kys@...rosoft.com,
	linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com, ssengar@...ux.microsoft.com, tglx@...utronix.de,
	wei.liu@...nel.org, x86@...nel.org
Subject: Re: [PATCH] x86/hyperv/vtl: Stop kernel from probing VTL0 low memory

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@...ux.microsoft.com>
> > Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
> > Signed-off-by: Naman Jain <namjain@...ux.microsoft.com>
> > ---
> >  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@...ux.microsoft.com>
> Reviewed-by: Roman Kisel <romank@...ux.microsoft.com>

Applied to hyperv-fixes. Thanks.