[PATCHv2 09/29] x86/tdx: Detect TDX at early kernel decompression time
From: Kirill A. Shutemov
Date: Mon Jan 24 2022 - 10:03:24 EST
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
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 size is
small enough and hence patching it will not bloat the image size a lot.
To support port I/O in decompression code, TDX must be detected before
the decompression code might do port I/O. Add support to detect for
TDX guest support before console_init() in the extract_kernel().
Detecting it above the console_init() is early enough for patching
port I/O.
Add an early_is_tdx_guest() interface to get the cached TDX guest
status in the decompression code.
The actual port I/O paravirtualization will come later in the series.
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
arch/x86/boot/compressed/Makefile | 1 +
arch/x86/boot/compressed/misc.c | 8 ++++++++
arch/x86/boot/compressed/misc.h | 2 ++
arch/x86/boot/compressed/tdx.c | 29 +++++++++++++++++++++++++++++
arch/x86/boot/compressed/tdx.h | 16 ++++++++++++++++
arch/x86/boot/cpuflags.c | 3 +--
arch/x86/boot/cpuflags.h | 1 +
arch/x86/include/asm/shared/tdx.h | 7 +++++++
arch/x86/include/asm/tdx.h | 4 +---
9 files changed, 66 insertions(+), 5 deletions(-)
create mode 100644 arch/x86/boot/compressed/tdx.c
create mode 100644 arch/x86/boot/compressed/tdx.h
create mode 100644 arch/x86/include/asm/shared/tdx.h
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 6115274fe10f..732f6b21ecbd 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -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
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index a4339cb2d247..d8373d766672 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -370,6 +370,14 @@ 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 oprations if needed.
+ */
+ early_tdx_detect();
+
console_init();
/*
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 16ed360b6692..0d8e275a9d96 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -28,6 +28,8 @@
#include <asm/bootparam.h>
#include <asm/desc_defs.h>
+#include "tdx.h"
+
#define BOOT_CTYPE_H
#include <linux/acpi.h>
diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
new file mode 100644
index 000000000000..6853376fe69a
--- /dev/null
+++ b/arch/x86/boot/compressed/tdx.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * tdx.c - Early boot code for TDX
+ */
+
+#include "../cpuflags.h"
+#include "../string.h"
+
+#include <asm/shared/tdx.h>
+
+static bool tdx_guest_detected;
+
+bool early_is_tdx_guest(void)
+{
+ return tdx_guest_detected;
+}
+
+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, 12))
+ return;
+
+ /* Cache TDX guest feature status */
+ tdx_guest_detected = true;
+}
diff --git a/arch/x86/boot/compressed/tdx.h b/arch/x86/boot/compressed/tdx.h
new file mode 100644
index 000000000000..18970c09512e
--- /dev/null
+++ b/arch/x86/boot/compressed/tdx.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2021 Intel Corporation */
+#ifndef BOOT_COMPRESSED_TDX_H
+#define BOOT_COMPRESSED_TDX_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_INTEL_TDX_GUEST
+void early_tdx_detect(void);
+bool early_is_tdx_guest(void);
+#else
+static inline void early_tdx_detect(void) { };
+static inline bool early_is_tdx_guest(void) { return false; }
+#endif
+
+#endif
diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c
index a0b75f73dc63..a83d67ec627d 100644
--- a/arch/x86/boot/cpuflags.c
+++ b/arch/x86/boot/cpuflags.c
@@ -71,8 +71,7 @@ int has_eflag(unsigned long mask)
# define EBX_REG "=b"
#endif
-static inline void cpuid_count(u32 id, u32 count,
- u32 *a, u32 *b, u32 *c, u32 *d)
+void cpuid_count(u32 id, u32 count, u32 *a, u32 *b, u32 *c, u32 *d)
{
asm volatile(".ifnc %%ebx,%3 ; movl %%ebx,%3 ; .endif \n\t"
"cpuid \n\t"
diff --git a/arch/x86/boot/cpuflags.h b/arch/x86/boot/cpuflags.h
index 2e20814d3ce3..475b8fde90f7 100644
--- a/arch/x86/boot/cpuflags.h
+++ b/arch/x86/boot/cpuflags.h
@@ -17,5 +17,6 @@ extern u32 cpu_vendor[3];
int has_eflag(unsigned long mask);
void get_cpuflags(void);
+void cpuid_count(u32 id, u32 count, u32 *a, u32 *b, u32 *c, u32 *d);
#endif
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
new file mode 100644
index 000000000000..12bede46d048
--- /dev/null
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -0,0 +1,7 @@
+#ifndef _ASM_X86_SHARED_TDX_H
+#define _ASM_X86_SHARED_TDX_H
+
+#define TDX_CPUID_LEAF_ID 0x21
+#define TDX_IDENT "IntelTDX "
+
+#endif
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 9b4714a45bb9..53f7dd0fbe58 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -5,9 +5,7 @@
#include <linux/init.h>
#include <asm/ptrace.h>
-
-#define TDX_CPUID_LEAF_ID 0x21
-#define TDX_IDENT "IntelTDX "
+#include <asm/shared/tdx.h>
#define TDX_HYPERCALL_STANDARD 0
--
2.34.1