Commit 4b05f815 authored by Kuppuswamy Sathyanarayanan's avatar Kuppuswamy Sathyanarayanan Committed by Dave Hansen
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x86/tdx: Detect TDX at early kernel decompression time 



The early decompression code does port I/O for its console output. But,
handling the decompression-time port I/O demands a different approach
from normal runtime because the IDT required to support #VE based port
I/O emulation is not yet set up. Paravirtualizing I/O calls during
the decompression step is acceptable because the decompression code
doesn't have a lot of call sites to IO instruction.

To support port I/O in decompression code, TDX must be detected before
the decompression code might do port I/O. Detect whether the kernel runs
in a TDX guest.

Add an early_is_tdx_guest() interface to query the cached TDX guest
status in the decompression code.

TDX is detected with CPUID. Make cpuid_count() accessible outside
boot/cpuflags.c.

TDX detection in the main kernel is very similar. Move common bits
into <asm/shared/tdx.h>.

The actual port I/O paravirtualization will come later in the series.

Signed-off-by: default avatarKuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarTony Luck <tony.luck@intel.com>
Reviewed-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20220405232939.73860-13-kirill.shutemov@linux.intel.com
parent 31d58c4e

arch/x86/boot/compressed/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ ifdef CONFIG_X86_64 
endif



vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o

vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o



vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o

efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a

arch/x86/boot/compressed/misc.c

+8 −0
Original line number Diff line number Diff line
@@ -371,6 +371,14 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, 
	lines = boot_params->screen_info.orig_video_lines;

	cols = boot_params->screen_info.orig_video_cols;



	/*

	 * Detect TDX guest environment.

	 *

	 * It has to be done before console_init() in order to use

	 * paravirtualized port I/O operations if needed.

	 */

	early_tdx_detect();



	console_init();



	/*

arch/x86/boot/compressed/misc.h

+2 −0
Original line number Diff line number Diff line
@@ -28,6 +28,8 @@ 
#include <asm/bootparam.h>

#include <asm/desc_defs.h>



#include "tdx.h"



#define BOOT_CTYPE_H

#include <linux/acpi.h>

arch/x86/boot/compressed/tdx.c

0 → 100644
+16 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include "../cpuflags.h"

#include "../string.h"



#include <asm/shared/tdx.h>



void early_tdx_detect(void)

{

	u32 eax, sig[3];



	cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2],  &sig[1]);



	if (memcmp(TDX_IDENT, sig, sizeof(sig)))

		return;

}

arch/x86/boot/compressed/tdx.h

0 → 100644
+13 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef BOOT_COMPRESSED_TDX_H

#define BOOT_COMPRESSED_TDX_H



#include <linux/types.h>



#ifdef CONFIG_INTEL_TDX_GUEST

void early_tdx_detect(void);

#else

static inline void early_tdx_detect(void) { };

#endif



#endif /* BOOT_COMPRESSED_TDX_H */