Re: [PATCH v1 01/14] x86/realmode: remove I/O port paravirtualization

[David Laight <david.laight.linux@gmail.com>]

On Tue, 20 Jan 2026 11:53:53 -0800
"H. Peter Anvin" <hpa@zytor.com> wrote:

> 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
                                                                  v

	David

> 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@zytor.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)