linux-kernel - [PATCH v1 01/14] x86/realmode: remove I/O port paravirtualization

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Message-ID: <20260120195407.1163051-2-hpa@zytor.com>
Date: Tue, 20 Jan 2026 11:53:53 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Thomas Gleixner <tglx@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Uros Bizjak <ubizjak@...il.com>, Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <kees@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Kiryl Shutsemau <kas@...nel.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        linux-coco@...ts.linux.dev, x86@...nel.org
Subject: [PATCH v1 01/14] x86/realmode: remove I/O port paravirtualization

In commit:

eb4ea1ae8f45 x86/boot: Port I/O: Allow to hook up alternative helpers

... paravirtualization hooks were added to (some!) of the port I/O
functions. However, they were only ever used in the 32/64-bit
"compressed" directory, and never made any sense in the real-mode
code, which is notoriously size sensitive.

Without these hooks, <asm/shared/io.h> is usable directly, so mode
io.h into the compressed/ directory and replace "io.h" with
<asm/shared/io.h> for the actual real-mode code.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
---
 arch/x86/boot/boot.h                | 2 +-
 arch/x86/boot/{ => compressed}/io.h | 0
 arch/x86/boot/compressed/misc.h     | 2 +-
 arch/x86/boot/compressed/tdx.c      | 2 +-
 arch/x86/boot/main.c                | 5 +----
 arch/x86/realmode/rm/wakemain.c     | 4 ----
 6 files changed, 4 insertions(+), 11 deletions(-)
 rename arch/x86/boot/{ => compressed}/io.h (100%)

diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 8e3eab34dff4..f185931283cb 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -18,6 +18,7 @@
 
 #ifndef __ASSEMBLER__
 
+#include <asm/shared/io.h>
 #include <linux/stdarg.h>
 #include <linux/types.h>
 #include <linux/edd.h>
@@ -26,7 +27,6 @@
 #include "bitops.h"
 #include "ctype.h"
 #include "cpuflags.h"
-#include "io.h"
 
 /* Useful macros */
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
diff --git a/arch/x86/boot/io.h b/arch/x86/boot/compressed/io.h
similarity index 100%
rename from arch/x86/boot/io.h
rename to arch/x86/boot/compressed/io.h
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index fd855e32c9b9..68957e7698ad 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -43,8 +43,8 @@
 
 #define BOOT_BOOT_H
 #include "../ctype.h"
-#include "../io.h"
 
+#include "io.h"
 #include "efi.h"
 
 #ifdef CONFIG_X86_64
diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
index 8451d6a1030c..00359dbe1f8c 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -2,7 +2,7 @@
 
 #include "../cpuflags.h"
 #include "../string.h"
-#include "../io.h"
+#include "io.h"
 #include "error.h"
 
 #include <vdso/limits.h>
diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
index 9d0fea18d3c8..da01ade4959e 100644
--- a/arch/x86/boot/main.c
+++ b/arch/x86/boot/main.c
@@ -15,10 +15,9 @@
 #include "boot.h"
 #include "string.h"
 
+/* Buffer for building the full "zero page" struct boot_params */
 struct boot_params boot_params __attribute__((aligned(16)));
 
-struct port_io_ops pio_ops;
-
 char *HEAP = _end;
 char *heap_end = _end;		/* Default end of heap = no heap */
 
@@ -132,8 +131,6 @@ static void init_heap(void)
 
 void main(void)
 {
-	init_default_io_ops();
-
 	/* First, copy the boot header into the "zeropage" */
 	copy_boot_params();
 
diff --git a/arch/x86/realmode/rm/wakemain.c b/arch/x86/realmode/rm/wakemain.c
index a6f4d8388ad8..1d6437e6d2ba 100644
--- a/arch/x86/realmode/rm/wakemain.c
+++ b/arch/x86/realmode/rm/wakemain.c
@@ -62,12 +62,8 @@ static void send_morse(const char *pattern)
 	}
 }
 
-struct port_io_ops pio_ops;
-
 void main(void)
 {
-	init_default_io_ops();
-
 	/* Kill machine if structures are wrong */
 	if (wakeup_header.real_magic != 0x12345678)
 		while (1)
-- 
2.52.0