Re: [PATCH 10/26] x86/tdx: Support TDX guest port I/O at decompression time

From: Kirill A. Shutemov
Date: Wed Jan 19 2022 - 10:49:00 EST

On Wed, Jan 19, 2022 at 02:35:09PM +0100, Borislav Petkov wrote:
> Raise hpa and tglx to To: for the general direction.
>
> Full mail is at
>
> https://lore.kernel.org/r/20220119115326.rw2aj3ho2mct4xxv@xxxxxxxxxxxxxxxxx
>
> On Wed, Jan 19, 2022 at 02:53:26PM +0300, Kirill A. Shutemov wrote:
> > Could you take a look if the diff below is the right direction?
> >
> > If yes, I will prepare a proper patches. My plan is 3 patches: introduce
> > <asm/shared/io.h>, add 'struct port_io_ops' for early boot, hook up
> > alternative 'struct port_io_ops' for TDX.
>
> Makes sense.
>
> > diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
> > index 34c9dbb6a47d..27ce7cef13aa 100644
> > --- a/arch/x86/boot/boot.h
> > +++ b/arch/x86/boot/boot.h
> > @@ -18,11 +18,14 @@
> >
> > #ifndef __ASSEMBLY__
> >
> > +#undef CONFIG_PARAVIRT
>
> Yeah, this is the stuff I'd like to avoid in boot/. Can we get rid of
> any ifdeffery in the shared/ namespace?
>
> I see this slow_down_io()-enforced CONFIG_PARAVIRT ifdeffery and that
> should not be there but in the ...asm/io.h kernel proper header. In the
> shared header we should have only basic functions which are shared by
> all.
>
> For the same reason I don't think the shared header should have those
> if (cc_platform_has... branches but just the basic bits with the asm
> wrappers.

Okay, makes sense. See the patch below.

> > @@ -370,6 +377,15 @@ 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;
> >
> > + port_io_ops = (const struct port_io_ops){
> > + .inb = inb,
> > + .inw = inw,
> > + .inl = inl,
> > + .outb = outb,
> > + .outw = outw,
> > + .outl = outl,
> > + };
>
> Why here and not statically defined above?

I tried to define

const struct port_io_ops default_pio_ops = {
.inb = inb,
.inw = inw,
.inl = inl,
.outb = outb,
.outw = outw,
.outl = outl,
};

make pio_ops a pointer and assign it here:

pio_ops = &default_pio_ops;

But it leads to an issue on linking:

ld.lld: error: Unexpected run-time relocations (.rela) detected!

I'm not sure how to deal with it. Any clues?

An updated patch:

diff --git a/arch/x86/boot/a20.c b/arch/x86/boot/a20.c
index a2b6b428922a..506e4dc0d519 100644
--- a/arch/x86/boot/a20.c
+++ b/arch/x86/boot/a20.c
@@ -12,6 +12,7 @@
*/

#include "boot.h"
+#include "io.h"

#define MAX_8042_LOOPS 100000
#define MAX_8042_FF 32
@@ -25,7 +26,7 @@ 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 +35,7 @@ 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 +100,13 @@ 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 +114,10 @@ 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 34c9dbb6a47d..22a474c5b3e8 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -23,6 +23,7 @@
#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"
@@ -35,40 +36,6 @@ extern struct boot_params boot_params;

#define cpu_relax() asm volatile("rep; nop")

-/* Basic port I/O */
-static inline void outb(u8 v, u16 port)
-{
- asm volatile("outb %0,%1" : : "a" (v), "dN" (port));
-}
-static inline u8 inb(u16 port)
-{
- u8 v;
- asm volatile("inb %1,%0" : "=a" (v) : "dN" (port));
- return v;
-}
-
-static inline void outw(u16 v, u16 port)
-{
- asm volatile("outw %0,%1" : : "a" (v), "dN" (port));
-}
-static inline u16 inw(u16 port)
-{
- u16 v;
- asm volatile("inw %1,%0" : "=a" (v) : "dN" (port));
- return v;
-}
-
-static inline void outl(u32 v, u16 port)
-{
- asm volatile("outl %0,%1" : : "a" (v), "dN" (port));
-}
-static inline u32 inl(u16 port)
-{
- u32 v;
- asm volatile("inl %1,%0" : "=a" (v) : "dN" (port));
- return v;
-}
-
static inline void io_delay(void)
{
const u16 DELAY_PORT = 0x80;
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.c b/arch/x86/boot/compressed/misc.c
index d8373d766672..f0906b39d3d7 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -15,9 +15,11 @@
#include "misc.h"
#include "error.h"
#include "pgtable.h"
+#include "tdx.h"
#include "../string.h"
#include "../voffset.h"
#include <asm/bootparam_utils.h>
+#include <asm/shared/io.h>

/*
* WARNING!!
@@ -47,6 +49,8 @@ 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 +107,12 @@ 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 +158,10 @@ 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 +376,15 @@ 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;

+ pio_ops = (const struct port_io_ops){
+ .inb = inb,
+ .inw = inw,
+ .inl = inl,
+ .outb = outb,
+ .outw = outw,
+ .outl = outl,
+ };
+
/*
* Detect TDX guest environment.
*
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 0d8e275a9d96..bf0fd98d5ce7 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -22,19 +22,17 @@
#include <linux/linkage.h>
#include <linux/screen_info.h>
#include <linux/elf.h>
-#include <linux/io.h>
#include <asm/page.h>
#include <asm/boot.h>
#include <asm/bootparam.h>
#include <asm/desc_defs.h>

-#include "tdx.h"
-
#define BOOT_CTYPE_H
#include <linux/acpi.h>

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

#ifdef CONFIG_X86_64
#define memptr long
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.c b/arch/x86/boot/compressed/tdx.c
index 50c8145bd0f3..07357147753f 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -5,12 +5,71 @@

#include "../cpuflags.h"
#include "../string.h"
+#include "../io.h"
+
+#include <vdso/limits.h>
+#include <uapi/asm/vmx.h>
+#include <asm/shared/io.h>
+#include <asm/tdx.h>

#define TDX_CPUID_LEAF_ID 0x21
#define TDX_IDENT "IntelTDX "

static bool tdx_guest_detected;

+bool early_is_tdx_guest(void)
+{
+ return tdx_guest_detected;
+}
+
+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);
+}
+
+static inline unsigned char tdx_inb(int port)
+{
+ return tdx_io_in(1, port);
+}
+
+static inline unsigned short tdx_inw(int port)
+{
+ return tdx_io_in(2, port);
+}
+
+static inline unsigned int tdx_inl(int port)
+{
+ return tdx_io_in(4, port);
+}
+
+static inline void tdx_outb(unsigned char value, int port)
+{
+ tdx_io_out(1, port, value);
+}
+
+static inline void tdx_outw(unsigned short value, int port)
+{
+ tdx_io_out(2, port, value);
+}
+
+static inline void tdx_outl(unsigned int value, int port)
+{
+ tdx_io_out(4, port, value);
+}
+
void early_tdx_detect(void)
{
u32 eax, sig[3];
@@ -22,9 +81,13 @@ void early_tdx_detect(void)

/* Cache TDX guest feature status */
tdx_guest_detected = true;
-}

-bool early_is_tdx_guest(void)
-{
- return tdx_guest_detected;
+ pio_ops = (struct port_io_ops) {
+ .inb = tdx_inb,
+ .inw = tdx_inw,
+ .inl = tdx_inl,
+ .outb = tdx_outb,
+ .outw = tdx_outw,
+ .outl = tdx_outl,
+ };
}
diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
index 023bf1c3de8b..5ccc3d1b8f97 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -4,6 +4,7 @@
* included from both the compressed kernel and the regular kernel.
*/
#include "boot.h"
+#include "io.h"

#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */

@@ -28,17 +29,17 @@ 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 +105,11 @@ 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..f75edad63eaa
--- /dev/null
+++ b/arch/x86/boot/io.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BOOT_IO_H
+#define BOOT_IO_H
+
+#include <linux/compiler_attributes.h>
+
+struct port_io_ops {
+ unsigned char (*inb)(int port);
+ unsigned short (*inw)(int port);
+ unsigned int (*inl)(int port);
+ void (*outb)(unsigned char v, int port);
+ void (*outw)(unsigned short v, int port);
+ void (*outl)(unsigned int v, int port);
+};
+
+extern struct port_io_ops pio_ops;
+
+#endif
diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
index e3add857c2c9..ae2eed21f62e 100644
--- a/arch/x86/boot/main.c
+++ b/arch/x86/boot/main.c
@@ -13,10 +13,13 @@
#include <linux/build_bug.h>

#include "boot.h"
+#include "io.h"
#include "string.h"

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 +136,15 @@ static void init_heap(void)

void main(void)
{
+ pio_ops = (struct port_io_ops){
+ .inb = inb,
+ .inw = inw,
+ .inl = inl,
+ .outb = outb,
+ .outw = outw,
+ .outl = outl,
+ };
+
/* 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..26d9c5b34b9f 100644
--- a/arch/x86/boot/pm.c
+++ b/arch/x86/boot/pm.c
@@ -11,6 +11,7 @@
*/

#include "boot.h"
+#include "io.h"
#include <asm/segment.h>

/*
@@ -25,7 +26,7 @@ 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 +36,9 @@ 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 +47,9 @@ 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..7675ed9afa55 100644
--- a/arch/x86/boot/tty.c
+++ b/arch/x86/boot/tty.c
@@ -12,6 +12,7 @@
*/

#include "boot.h"
+#include "io.h"

int early_serial_base;

@@ -29,10 +30,10 @@ 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/include/asm/io.h b/arch/x86/include/asm/io.h
index f6d91ecb8026..8ce0a40379de 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -44,6 +44,7 @@
#include <asm/page.h>
#include <asm/early_ioremap.h>
#include <asm/pgtable_types.h>
+#include <asm/shared/io.h>

#define build_mmio_read(name, size, type, reg, barrier) \
static inline type name(const volatile void __iomem *addr) \
@@ -258,20 +259,6 @@ static inline void slow_down_io(void)
#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)); \
-} \
- \
-static inline unsigned type in##bwl(int port) \
-{ \
- unsigned type value; \
- asm volatile("in" #bwl " %w1, %" #bw "0" \
- : "=a"(value) : "Nd"(port)); \
- return value; \
-} \
- \
static inline void out##bwl##_p(unsigned type value, int port) \
{ \
out##bwl(value, port); \
@@ -320,10 +307,8 @@ static inline void ins##bwl(int port, void *addr, unsigned long count) \
BUILDIO(b, b, char)
BUILDIO(w, w, short)
BUILDIO(l, , int)
+#undef BUILDIO

-#define inb inb
-#define inw inw
-#define inl inl
#define inb_p inb_p
#define inw_p inw_p
#define inl_p inl_p
@@ -331,9 +316,6 @@ BUILDIO(l, , int)
#define insw insw
#define insl insl

-#define outb outb
-#define outw outw
-#define outl outl
#define outb_p outb_p
#define outw_p outw_p
#define outl_p outl_p
diff --git a/arch/x86/include/asm/shared/io.h b/arch/x86/include/asm/shared/io.h
new file mode 100644
index 000000000000..f17247f6c471
--- /dev/null
+++ b/arch/x86/include/asm/shared/io.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SHARED_IO_H
+#define _ASM_X86_SHARED_IO_H
+
+#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)); \
+} \
+ \
+static inline unsigned type in##bwl(int port) \
+{ \
+ unsigned type value; \
+ asm volatile("in" #bwl " %w1, %" #bw "0" \
+ : "=a"(value) : "Nd"(port)); \
+ return value; \
+}
+
+BUILDIO(b, b, char)
+BUILDIO(w, w, short)
+BUILDIO(l, , int)
+#undef BUILDIO
+
+#define inb inb
+#define inw inw
+#define inl inl
+#define outb outb
+#define outw outw
+#define outl outl
+
+#endif
--
Kirill A. Shutemov