linux-kernel - [PATCH AUTOSEL 6.13 01/16] x86/hyperv/vtl: Stop kernel from probing VTL0 low memory

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Message-Id: <20250317163725.1892824-1-sashal@kernel.org>
Date: Mon, 17 Mar 2025 12:37:10 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Naman Jain <namjain@...ux.microsoft.com>,
	Saurabh Sengar <ssengar@...ux.microsoft.com>,
	Roman Kisel <romank@...ux.microsoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	kys@...rosoft.com,
	haiyangz@...rosoft.com,
	decui@...rosoft.com,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	x86@...nel.org,
	linux-hyperv@...r.kernel.org
Subject: [PATCH AUTOSEL 6.13 01/16] x86/hyperv/vtl: Stop kernel from probing VTL0 low memory

From: Naman Jain <namjain@...ux.microsoft.com>

[ Upstream commit 59115e2e25f42924181055ed7cc1d123af7598b7 ]

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>
Tested-by: Roman Kisel <romank@...ux.microsoft.com>
Reviewed-by: Roman Kisel <romank@...ux.microsoft.com>
Link: https://lore.kernel.org/r/20250116061224.1701-1-namjain@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@...nel.org>
Message-ID: <20250116061224.1701-1-namjain@...ux.microsoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 04775346369c5..d04ccd4b3b4af 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;
-- 
2.39.5