linux-kernel - [PATCH v4 05/10] x86/hyperv/vtl: Set real_mode_header in hv_vtl_init

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Message-Id: <20250603-rneri-wakeup-mailbox-v4-5-d533272b7232@linux.intel.com>
Date: Tue, 03 Jun 2025 17:15:17 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: x86@...nel.org, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Rob Herring <robh@...nel.org>, 
 "K. Y. Srinivasan" <kys@...rosoft.com>, 
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, 
 Dexuan Cui <decui@...rosoft.com>, Michael Kelley <mhklinux@...look.com>, 
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Saurabh Sengar <ssengar@...ux.microsoft.com>, 
 Chris Oo <cho@...rosoft.com>, 
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, 
 linux-hyperv@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, 
 "Ravi V. Shankar" <ravi.v.shankar@...el.com>, 
 Ricardo Neri <ricardo.neri@...el.com>, 
 Yunhong Jiang <yunhong.jiang@...ux.intel.com>, 
 Thomas Gleixner <tglx@...utronix.de>, 
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: [PATCH v4 05/10] x86/hyperv/vtl: Set real_mode_header in
 hv_vtl_init_platform()

From: Yunhong Jiang <yunhong.jiang@...ux.intel.com>

Hyper-V VTL clears x86_platform.realmode_{init(), reserve()} in
hv_vtl_platform_init() whereas it sets real_mode_header later in
hv_vtl_early_init(). There is no need to deal with the real mode memory
in two places: x86_platform.realmode_init() is invoked much later via an
early_initcall.

Set real_mode_header in hv_vtl_init_platform() to keep all code dealing
with memory for the real mode trampoline in one place. Besides making the
code more readable, it prepares it for a subsequent changeset in which the
behavior needs to change to support Hyper-V VTL guests in TDX environment.

Reviewed-by: Michael Kelley <mhklinux@...look.com>
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Yunhong Jiang <yunhong.jiang@...ux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
---
Changes since v3:
 - Added Reviewed-by tag from Michael. Thanks!

Changes since v2:
 - Edited the commit message for clarity.

Changes since v1:
 - Introduced this patch.
---
 arch/x86/hyperv/hv_vtl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 4580936dcb03..6bd183ee484f 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -60,6 +60,7 @@ void __init hv_vtl_init_platform(void)

 	x86_platform.realmode_reserve = x86_init_noop;
 	x86_platform.realmode_init = x86_init_noop;
+	real_mode_header = &hv_vtl_real_mode_header;
 	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;
@@ -279,7 +280,6 @@ int __init hv_vtl_early_init(void)
 		panic("XSAVE has to be disabled as it is not supported by this module.\n"
 			  "Please add 'noxsave' to the kernel command line.\n");

-	real_mode_header = &hv_vtl_real_mode_header;
 	apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);

 	return 0;

-- 
2.43.0