linux-kernel - RE: [PATCH v3 08/13] x86/hyperv/vtl: Set real_mode_header in hv_vtl_init

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Message-ID:
 <SN6PR02MB4157071AA31B1D5AEEF36E5CD49FA@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Tue, 20 May 2025 01:24:09 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, "x86@...nel.org"
	<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>
CC: "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, Saurabh Sengar
	<ssengar@...ux.microsoft.com>, Chris Oo <cho@...rosoft.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>, "Kirill A.
 Shutemov" <kirill.shutemov@...ux.intel.com>, "linux-acpi@...r.kernel.org"
	<linux-acpi@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Ricardo Neri <ricardo.neri@...el.com>
Subject: RE: [PATCH v3 08/13] x86/hyperv/vtl: Set real_mode_header in
 hv_vtl_init_platform()

From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> Sent: Saturday, May 3, 2025 12:15 PM
> 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.
> 
> 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 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

Reviewed-by: Michael Kelley <mhklinux@...look.com>