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Subject[PATCHv5 15/30] x86/boot: Port I/O: allow to hook up alternative helpers
Date
Port I/O instructions trigger #VE in the TDX environment. In response to
the exception, kernel emulates these instructions using hypercalls.

But during early boot, on the decompression stage, it is cumbersome to
deal with #VE. It is cleaner to go to hypercalls directly, bypassing #VE
handling.

Add a way to hook up alternative port I/O helpers in the boot stub with
a new pio_ops structure. For now, set the ops structure to just call
the normal I/O operation functions.

The approach has down sides: TDX boot will fail if any code bypass
pio_ops and go for direct port I/O helper. The failure will only be
visible on TDX boot (or other user of alternative pio_ops).

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
---
arch/x86/boot/a20.c | 14 ++++++------
arch/x86/boot/boot.h | 2 +-
arch/x86/boot/compressed/misc.c | 18 ++++++++++------
arch/x86/boot/compressed/misc.h | 2 +-
arch/x86/boot/early_serial_console.c | 28 ++++++++++++------------
arch/x86/boot/io.h | 32 ++++++++++++++++++++++++++++
arch/x86/boot/main.c | 4 ++++
arch/x86/boot/pm.c | 10 ++++-----
arch/x86/boot/tty.c | 4 ++--
arch/x86/boot/video-vga.c | 6 +++---
arch/x86/boot/video.h | 8 ++++---
arch/x86/realmode/rm/wakemain.c | 14 +++++++-----
12 files changed, 95 insertions(+), 47 deletions(-)
create mode 100644 arch/x86/boot/io.h

diff --git a/arch/x86/boot/a20.c b/arch/x86/boot/a20.c
index a2b6b428922a..7f6dd5cc4670 100644
--- a/arch/x86/boot/a20.c
+++ b/arch/x86/boot/a20.c
@@ -25,7 +25,7 @@ static int empty_8042(void)
while (loops--) {
io_delay();

- status = inb(0x64);
+ status = pio_ops.inb(0x64);
if (status == 0xff) {
/* FF is a plausible, but very unlikely status */
if (!--ffs)
@@ -34,7 +34,7 @@ static int empty_8042(void)
if (status & 1) {
/* Read and discard input data */
io_delay();
- (void)inb(0x60);
+ (void)pio_ops.inb(0x60);
} else if (!(status & 2)) {
/* Buffers empty, finished! */
return 0;
@@ -99,13 +99,13 @@ static void enable_a20_kbc(void)
{
empty_8042();

- outb(0xd1, 0x64); /* Command write */
+ pio_ops.outb(0xd1, 0x64); /* Command write */
empty_8042();

- outb(0xdf, 0x60); /* A20 on */
+ pio_ops.outb(0xdf, 0x60); /* A20 on */
empty_8042();

- outb(0xff, 0x64); /* Null command, but UHCI wants it */
+ pio_ops.outb(0xff, 0x64); /* Null command, but UHCI wants it */
empty_8042();
}

@@ -113,10 +113,10 @@ static void enable_a20_fast(void)
{
u8 port_a;

- port_a = inb(0x92); /* Configuration port A */
+ port_a = pio_ops.inb(0x92); /* Configuration port A */
port_a |= 0x02; /* Enable A20 */
port_a &= ~0x01; /* Do not reset machine */
- outb(port_a, 0x92);
+ pio_ops.outb(port_a, 0x92);
}

/*
diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 22a474c5b3e8..bd8f640ca15f 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -23,10 +23,10 @@
#include <linux/edd.h>
#include <asm/setup.h>
#include <asm/asm.h>
-#include <asm/shared/io.h>
#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/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 2b1169869b96..ff0e1b977514 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -47,6 +47,8 @@ void *memmove(void *dest, const void *src, size_t n);
*/
struct boot_params *boot_params;

+struct port_io_ops pio_ops;
+
memptr free_mem_ptr;
memptr free_mem_end_ptr;

@@ -103,10 +105,12 @@ static void serial_putchar(int ch)
{
unsigned timeout = 0xffff;

- while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
+ while ((pio_ops.inb(early_serial_base + LSR) & XMTRDY) == 0 &&
+ --timeout) {
cpu_relax();
+ }

- outb(ch, early_serial_base + TXR);
+ pio_ops.outb(ch, early_serial_base + TXR);
}

void __putstr(const char *s)
@@ -152,10 +156,10 @@ void __putstr(const char *s)
boot_params->screen_info.orig_y = y;

pos = (x + cols * y) * 2; /* Update cursor position */
- outb(14, vidport);
- outb(0xff & (pos >> 9), vidport+1);
- outb(15, vidport);
- outb(0xff & (pos >> 1), vidport+1);
+ pio_ops.outb(14, vidport);
+ pio_ops.outb(0xff & (pos >> 9), vidport+1);
+ pio_ops.outb(15, vidport);
+ pio_ops.outb(0xff & (pos >> 1), vidport+1);
}

void __puthex(unsigned long value)
@@ -370,6 +374,8 @@ 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;

+ init_default_io_ops();
+
/*
* Detect TDX guest environment.
*
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 8a253e85f990..ea71cf3d64e1 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -26,7 +26,6 @@
#include <asm/boot.h>
#include <asm/bootparam.h>
#include <asm/desc_defs.h>
-#include <asm/shared/io.h>

#include "tdx.h"

@@ -35,6 +34,7 @@

#define BOOT_BOOT_H
#include "../ctype.h"
+#include "../io.h"

#ifdef CONFIG_X86_64
#define memptr long
diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
index 023bf1c3de8b..03e43d770571 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -28,17 +28,17 @@ static void early_serial_init(int port, int baud)
unsigned char c;
unsigned divisor;

- outb(0x3, port + LCR); /* 8n1 */
- outb(0, port + IER); /* no interrupt */
- outb(0, port + FCR); /* no fifo */
- outb(0x3, port + MCR); /* DTR + RTS */
+ pio_ops.outb(0x3, port + LCR); /* 8n1 */
+ pio_ops.outb(0, port + IER); /* no interrupt */
+ pio_ops.outb(0, port + FCR); /* no fifo */
+ pio_ops.outb(0x3, port + MCR); /* DTR + RTS */

divisor = 115200 / baud;
- c = inb(port + LCR);
- outb(c | DLAB, port + LCR);
- outb(divisor & 0xff, port + DLL);
- outb((divisor >> 8) & 0xff, port + DLH);
- outb(c & ~DLAB, port + LCR);
+ c = pio_ops.inb(port + LCR);
+ pio_ops.outb(c | DLAB, port + LCR);
+ pio_ops.outb(divisor & 0xff, port + DLL);
+ pio_ops.outb((divisor >> 8) & 0xff, port + DLH);
+ pio_ops.outb(c & ~DLAB, port + LCR);

early_serial_base = port;
}
@@ -104,11 +104,11 @@ static unsigned int probe_baud(int port)
unsigned char lcr, dll, dlh;
unsigned int quot;

- lcr = inb(port + LCR);
- outb(lcr | DLAB, port + LCR);
- dll = inb(port + DLL);
- dlh = inb(port + DLH);
- outb(lcr, port + LCR);
+ lcr = pio_ops.inb(port + LCR);
+ pio_ops.outb(lcr | DLAB, port + LCR);
+ dll = pio_ops.inb(port + DLL);
+ dlh = pio_ops.inb(port + DLH);
+ pio_ops.outb(lcr, port + LCR);
quot = (dlh << 8) | dll;

return BASE_BAUD / quot;
diff --git a/arch/x86/boot/io.h b/arch/x86/boot/io.h
new file mode 100644
index 000000000000..87dc8ee5d15f
--- /dev/null
+++ b/arch/x86/boot/io.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BOOT_IO_H
+#define BOOT_IO_H
+
+#include <asm/shared/io.h>
+
+struct port_io_ops {
+ u8 (*inb)(u16 port);
+ u16 (*inw)(u16 port);
+ u32 (*inl)(u16 port);
+ void (*outb)(u8 v, u16 port);
+ void (*outw)(u16 v, u16 port);
+ void (*outl)(u32 v, u16 port);
+};
+
+extern struct port_io_ops pio_ops;
+
+/*
+ * Use the normal I/O instructions by default.
+ * TDX guests override these to use hypercalls.
+ */
+static inline void init_default_io_ops(void)
+{
+ pio_ops.inb = inb;
+ pio_ops.inw = inw;
+ pio_ops.inl = inl;
+ pio_ops.outb = outb;
+ pio_ops.outw = outw;
+ pio_ops.outl = outl;
+}
+
+#endif
diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
index e3add857c2c9..1202d4f8a390 100644
--- a/arch/x86/boot/main.c
+++ b/arch/x86/boot/main.c
@@ -17,6 +17,8 @@

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 */

@@ -133,6 +135,8 @@ 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/boot/pm.c b/arch/x86/boot/pm.c
index 40031a614712..4180b6a264c9 100644
--- a/arch/x86/boot/pm.c
+++ b/arch/x86/boot/pm.c
@@ -25,7 +25,7 @@ static void realmode_switch_hook(void)
: "eax", "ebx", "ecx", "edx");
} else {
asm volatile("cli");
- outb(0x80, 0x70); /* Disable NMI */
+ pio_ops.outb(0x80, 0x70); /* Disable NMI */
io_delay();
}
}
@@ -35,9 +35,9 @@ static void realmode_switch_hook(void)
*/
static void mask_all_interrupts(void)
{
- outb(0xff, 0xa1); /* Mask all interrupts on the secondary PIC */
+ pio_ops.outb(0xff, 0xa1); /* Mask all interrupts on the secondary PIC */
io_delay();
- outb(0xfb, 0x21); /* Mask all but cascade on the primary PIC */
+ pio_ops.outb(0xfb, 0x21); /* Mask all but cascade on the primary PIC */
io_delay();
}

@@ -46,9 +46,9 @@ static void mask_all_interrupts(void)
*/
static void reset_coprocessor(void)
{
- outb(0, 0xf0);
+ pio_ops.outb(0, 0xf0);
io_delay();
- outb(0, 0xf1);
+ pio_ops.outb(0, 0xf1);
io_delay();
}

diff --git a/arch/x86/boot/tty.c b/arch/x86/boot/tty.c
index f7eb976b0a4b..ee8700682801 100644
--- a/arch/x86/boot/tty.c
+++ b/arch/x86/boot/tty.c
@@ -29,10 +29,10 @@ static void __section(".inittext") serial_putchar(int ch)
{
unsigned timeout = 0xffff;

- while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
+ while ((pio_ops.inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
cpu_relax();

- outb(ch, early_serial_base + TXR);
+ pio_ops.outb(ch, early_serial_base + TXR);
}

static void __section(".inittext") bios_putchar(int ch)
diff --git a/arch/x86/boot/video-vga.c b/arch/x86/boot/video-vga.c
index 4816cb9cf996..17baac542ee7 100644
--- a/arch/x86/boot/video-vga.c
+++ b/arch/x86/boot/video-vga.c
@@ -131,7 +131,7 @@ static void vga_set_80x43(void)
/* I/O address of the VGA CRTC */
u16 vga_crtc(void)
{
- return (inb(0x3cc) & 1) ? 0x3d4 : 0x3b4;
+ return (pio_ops.inb(0x3cc) & 1) ? 0x3d4 : 0x3b4;
}

static void vga_set_480_scanlines(void)
@@ -148,10 +148,10 @@ static void vga_set_480_scanlines(void)
out_idx(0xdf, crtc, 0x12); /* Vertical display end */
out_idx(0xe7, crtc, 0x15); /* Vertical blank start */
out_idx(0x04, crtc, 0x16); /* Vertical blank end */
- csel = inb(0x3cc);
+ csel = pio_ops.inb(0x3cc);
csel &= 0x0d;
csel |= 0xe2;
- outb(csel, 0x3c2);
+ pio_ops.outb(csel, 0x3c2);
}

static void vga_set_vertical_end(int lines)
diff --git a/arch/x86/boot/video.h b/arch/x86/boot/video.h
index 04bde0bb2003..87a5f726e731 100644
--- a/arch/x86/boot/video.h
+++ b/arch/x86/boot/video.h
@@ -15,6 +15,8 @@

#include <linux/types.h>

+#include "boot.h"
+
/*
* This code uses an extended set of video mode numbers. These include:
* Aliases for standard modes
@@ -96,13 +98,13 @@ extern int graphic_mode; /* Graphics mode with linear frame buffer */
/* Accessing VGA indexed registers */
static inline u8 in_idx(u16 port, u8 index)
{
- outb(index, port);
- return inb(port+1);
+ pio_ops.outb(index, port);
+ return pio_ops.inb(port+1);
}

static inline void out_idx(u8 v, u16 port, u8 index)
{
- outw(index+(v << 8), port);
+ pio_ops.outw(index+(v << 8), port);
}

/* Writes a value to an indexed port and then reads the port again */
diff --git a/arch/x86/realmode/rm/wakemain.c b/arch/x86/realmode/rm/wakemain.c
index 1d6437e6d2ba..8c2eb2a829f1 100644
--- a/arch/x86/realmode/rm/wakemain.c
+++ b/arch/x86/realmode/rm/wakemain.c
@@ -17,18 +17,18 @@ static void beep(unsigned int hz)
} else {
u16 div = 1193181/hz;

- outb(0xb6, 0x43); /* Ctr 2, squarewave, load, binary */
+ pio_ops.outb(0xb6, 0x43); /* Ctr 2, squarewave, load, binary */
io_delay();
- outb(div, 0x42); /* LSB of counter */
+ pio_ops.outb(div, 0x42); /* LSB of counter */
io_delay();
- outb(div >> 8, 0x42); /* MSB of counter */
+ pio_ops.outb(div >> 8, 0x42); /* MSB of counter */
io_delay();

enable = 0x03; /* Turn on speaker */
}
- inb(0x61); /* Dummy read of System Control Port B */
+ pio_ops.inb(0x61); /* Dummy read of System Control Port B */
io_delay();
- outb(enable, 0x61); /* Enable timer 2 output to speaker */
+ pio_ops.outb(enable, 0x61); /* Enable timer 2 output to speaker */
io_delay();
}

@@ -62,8 +62,12 @@ 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)
--
2.34.1
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