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: 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: Tony Luck <tony.luck@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20220405232939.73860-13-kirill.shutemov@linux.intel.com

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 6115274..732f6b2 100644 (file)
--- 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 1cdcaf3..e8142e9 100644 (file)
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -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();
 
        /*

diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 16ed360..0d8e275 100644 (file)
--- 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 (file)
index 0000000..5f6d01a
--- /dev/null
+++ b/arch/x86/boot/compressed/tdx.c
@@ -0,0 +1,16 @@
+// 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;
+}

diff --git a/arch/x86/boot/compressed/tdx.h b/arch/x86/boot/compressed/tdx.h
new file mode 100644 (file)
index 0000000..9055482
--- /dev/null
+++ b/arch/x86/boot/compressed/tdx.h
@@ -0,0 +1,13 @@
+/* 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 */

diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c
index a0b75f7..a83d67e 100644 (file)
--- 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 2e20814..475b8fd 100644 (file)
--- 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 (file)
index 0000000..8209ba9
--- /dev/null
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SHARED_TDX_H
+#define _ASM_X86_SHARED_TDX_H
+
+#define TDX_CPUID_LEAF_ID      0x21
+#define TDX_IDENT              "IntelTDX    "
+
+#endif /* _ASM_X86_SHARED_TDX_H */

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index cbd61e1..81a1ec1 100644 (file)
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -7,9 +7,7 @@
 #include <linux/init.h>
 #include <linux/bits.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