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Subject[PATCH 10/26] x86/tdx: Support TDX guest port I/O at decompression time
Date
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Port IO triggers a #VE exception in TDX guests. During normal runtime,
the kernel will handle those exceptions for any port IO.

But for the early code in the decompressor, #VE cannot be used because
the IDT needed for handling the exception is not set up.

Replace IN/OUT instructions with TDX IO hypercalls by defining helper
macros __in/__out and by re-defining them in the decompressor code.
Also, since TDX IO hypercall requires an IO size parameter, allow
__in/__out macros to accept size as an input parameter.

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/boot/compressed/Makefile | 1 +
arch/x86/boot/compressed/misc.h | 8 ++++--
arch/x86/boot/compressed/tdcall.S | 3 +++
arch/x86/boot/compressed/tdx.h | 44 +++++++++++++++++++++++++++++++
arch/x86/include/asm/io.h | 16 ++++++++---
5 files changed, 66 insertions(+), 6 deletions(-)
create mode 100644 arch/x86/boot/compressed/tdcall.S

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 22a2a6cc2ab4..1bfe30ebadbe 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -99,6 +99,7 @@ endif

vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o
+vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdcall.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.h b/arch/x86/boot/compressed/misc.h
index 0d8e275a9d96..6502adf71a2f 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -19,6 +19,12 @@
/* cpu_feature_enabled() cannot be used this early */
#define USE_EARLY_PGTABLE_L5

+/*
+ * Redefine __in/__out macros via tdx.h before including
+ * linux/io.h.
+ */
+#include "tdx.h"
+
#include <linux/linkage.h>
#include <linux/screen_info.h>
#include <linux/elf.h>
@@ -28,8 +34,6 @@
#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/tdcall.S b/arch/x86/boot/compressed/tdcall.S
new file mode 100644
index 000000000000..aafadc136c88
--- /dev/null
+++ b/arch/x86/boot/compressed/tdcall.S
@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include "../../kernel/tdcall.S"
diff --git a/arch/x86/boot/compressed/tdx.h b/arch/x86/boot/compressed/tdx.h
index 18970c09512e..5d39608a2af4 100644
--- a/arch/x86/boot/compressed/tdx.h
+++ b/arch/x86/boot/compressed/tdx.h
@@ -6,8 +6,52 @@
#include <linux/types.h>

#ifdef CONFIG_INTEL_TDX_GUEST
+
+#include <vdso/limits.h>
+#include <uapi/asm/vmx.h>
+#include <asm/tdx.h>
+
void early_tdx_detect(void);
bool early_is_tdx_guest(void);
+
+static inline unsigned int tdx_io_in(int size, int port)
+{
+ struct tdx_hypercall_output out;
+
+ __tdx_hypercall(TDX_HYPERCALL_STANDARD, EXIT_REASON_IO_INSTRUCTION,
+ size, 0, port, 0, &out);
+
+ return out.r10 ? UINT_MAX : out.r11;
+}
+
+static inline void tdx_io_out(int size, int port, u64 value)
+{
+ struct tdx_hypercall_output out;
+
+ __tdx_hypercall(TDX_HYPERCALL_STANDARD, EXIT_REASON_IO_INSTRUCTION,
+ size, 1, port, value, &out);
+}
+
+#define __out(bwl, bw, sz) \
+do { \
+ if (early_is_tdx_guest()) { \
+ tdx_io_out(sz, port, value); \
+ } else { \
+ asm volatile("out" #bwl " %" #bw "0, %w1" : : \
+ "a"(value), "Nd"(port)); \
+ } \
+} while (0)
+
+#define __in(bwl, bw, sz) \
+do { \
+ if (early_is_tdx_guest()) { \
+ value = tdx_io_in(sz, port); \
+ } else { \
+ asm volatile("in" #bwl " %w1, %" #bw "0" : \
+ "=a"(value) : "Nd"(port)); \
+ } \
+} while (0)
+
#else
static inline void early_tdx_detect(void) { };
static inline bool early_is_tdx_guest(void) { return false; }
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index f6d91ecb8026..f5bb8972b4b2 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -257,18 +257,26 @@ static inline void slow_down_io(void)

#endif

+#ifndef __out
+#define __out(bwl, bw, sz) \
+ asm volatile("out" #bwl " %" #bw "0, %w1" : : "a"(value), "Nd"(port))
+#endif
+
+#ifndef __in
+#define __in(bwl, bw, sz) \
+ asm volatile("in" #bwl " %w1, %" #bw "0" : "=a"(value) : "Nd"(port))
+#endif
+
#define BUILDIO(bwl, bw, type) \
static inline void out##bwl(unsigned type value, int port) \
{ \
- asm volatile("out" #bwl " %" #bw "0, %w1" \
- : : "a"(value), "Nd"(port)); \
+ __out(bwl, bw, sizeof(type)); \
} \
\
static inline unsigned type in##bwl(int port) \
{ \
unsigned type value; \
- asm volatile("in" #bwl " %w1, %" #bw "0" \
- : "=a"(value) : "Nd"(port)); \
+ __in(bwl, bw, sizeof(type)); \
return value; \
} \
\
--
2.32.0
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