linux/arch/x86/realmode/rm/header.S
Sean Christopherson ff2e64684f x86/boot: Add a trampoline for booting APs via firmware handoff
Historically, x86 platforms have booted secondary processors (APs)
using INIT followed by the start up IPI (SIPI) messages. In regular
VMs, this boot sequence is supported by the VMM emulation. But such a
wakeup model is fatal for secure VMs like TDX in which VMM is an
untrusted entity. To address this issue, a new wakeup model was added
in ACPI v6.4, in which firmware (like TDX virtual BIOS) will help boot
the APs. More details about this wakeup model can be found in ACPI
specification v6.4, the section titled "Multiprocessor Wakeup Structure".

Since the existing trampoline code requires processors to boot in real
mode with 16-bit addressing, it will not work for this wakeup model
(because it boots the AP in 64-bit mode). To handle it, extend the
trampoline code to support 64-bit mode firmware handoff. Also, extend
IDT and GDT pointers to support 64-bit mode hand off.

There is no TDX-specific detection for this new boot method. The kernel
will rely on it as the sole boot method whenever the new ACPI structure
is present.

The ACPI table parser for the MADT multiprocessor wake up structure and
the wakeup method that uses this structure will be added by the following
patch in this series.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20220405232939.73860-21-kirill.shutemov@linux.intel.com
2022-04-07 08:27:52 -07:00

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1.0 KiB
ArmAsm

/* SPDX-License-Identifier: GPL-2.0 */
/*
* Real-mode blob header; this should match realmode.h and be
* readonly; for mutable data instead add pointers into the .data
* or .bss sections as appropriate.
*/
#include <linux/linkage.h>
#include <asm/page_types.h>
#include <asm/segment.h>
#include "realmode.h"
.section ".header", "a"
.balign 16
SYM_DATA_START(real_mode_header)
.long pa_text_start
.long pa_ro_end
/* SMP trampoline */
.long pa_trampoline_start
.long pa_trampoline_header
#ifdef CONFIG_AMD_MEM_ENCRYPT
.long pa_sev_es_trampoline_start
#endif
#ifdef CONFIG_X86_64
.long pa_trampoline_start64
.long pa_trampoline_pgd;
#endif
/* ACPI S3 wakeup */
#ifdef CONFIG_ACPI_SLEEP
.long pa_wakeup_start
.long pa_wakeup_header
#endif
/* APM/BIOS reboot */
.long pa_machine_real_restart_asm
#ifdef CONFIG_X86_64
.long __KERNEL32_CS
#endif
SYM_DATA_END(real_mode_header)
/* End signature, used to verify integrity */
.section ".signature","a"
.balign 4
SYM_DATA(end_signature, .long REALMODE_END_SIGNATURE)