[PATCHv6 16/30] x86/boot: Port I/O: add decompression-time support for TDX

Kirill A. Shutemov
2022-03-16T02:11:19Z

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.

Hook up TDX-specific port I/O helpers if booting in TDX environment.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
---
arch/x86/boot/compressed/Makefile | 2 +-
arch/x86/boot/compressed/tdcall.S | 3 ++
arch/x86/boot/compressed/tdx.c | 79 +++++++++++++++++++++++++++++++
arch/x86/include/asm/shared/tdx.h | 29 ++++++++++++
arch/x86/include/asm/tdx.h | 24 ----------
5 files changed, 112 insertions(+), 25 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 732f6b21ecbd..8fd0e6ae2e1f 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -101,7 +101,7 @@ ifdef CONFIG_X86_64
endif

vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
-vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o
+vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(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/tdcall.S b/arch/x86/boot/compressed/tdcall.S
new file mode 100644
index 000000000000..46d0495e0d3a
--- /dev/null
+++ b/arch/x86/boot/compressed/tdcall.S
@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include "../../coco/tdx/tdcall.S"
diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
index d4f195e9d1ef..775ecdc16f90 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -2,6 +2,11 @@

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

#include <asm/shared/tdx.h>

@@ -12,6 +17,72 @@ bool early_is_tdx_guest(void)
return tdx_guest_detected;
}

+/* Called from __tdx_hypercall() for unrecoverable failure */
+void __tdx_hypercall_failed(void)
+{
+ error("TDVMCALL failed. TDX module bug?");
+}
+
+static inline unsigned int tdx_io_in(int size, u16 port)
+{
+ struct tdx_hypercall_args args = {
+ .r10 = TDX_HYPERCALL_STANDARD,
+ .r11 = EXIT_REASON_IO_INSTRUCTION,
+ .r12 = size,
+ .r13 = 0,
+ .r14 = port,
+ };
+
+ if (__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT))
+ return UINT_MAX;
+
+ return args.r11;
+}
+
+static inline void tdx_io_out(int size, u16 port, u32 value)
+{
+ struct tdx_hypercall_args args = {
+ .r10 = TDX_HYPERCALL_STANDARD,
+ .r11 = EXIT_REASON_IO_INSTRUCTION,
+ .r12 = size,
+ .r13 = 1,
+ .r14 = port,
+ .r15 = value,
+ };
+
+ __tdx_hypercall(&args, 0);
+}
+
+static inline u8 tdx_inb(u16 port)
+{
+ return tdx_io_in(1, port);
+}
+
+static inline u16 tdx_inw(u16 port)
+{
+ return tdx_io_in(2, port);
+}
+
+static inline u32 tdx_inl(u16 port)
+{
+ return tdx_io_in(4, port);
+}
+
+static inline void tdx_outb(u8 value, u16 port)
+{
+ tdx_io_out(1, port, value);
+}
+
+static inline void tdx_outw(u16 value, u16 port)
+{
+ tdx_io_out(2, port, value);
+}
+
+static inline void tdx_outl(u32 value, u16 port)
+{
+ tdx_io_out(4, port, value);
+}
+
void early_tdx_detect(void)
{
u32 eax, sig[3];
@@ -23,4 +94,12 @@ void early_tdx_detect(void)

/* Cache TDX guest feature status */
tdx_guest_detected = true;
+
+ /* Use hypercalls instead of I/O instructions */
+ inb = tdx_inb;
+ inw = tdx_inw;
+ inl = tdx_inl;
+ outb = tdx_outb;
+ outw = tdx_outw;
+ outl = tdx_outl;
}
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 8209ba9ffe1a..51bce6351124 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -2,7 +2,36 @@
#ifndef _ASM_X86_SHARED_TDX_H
#define _ASM_X86_SHARED_TDX_H

+#include <linux/bits.h>
+#include <linux/types.h>
+
+#define TDX_HYPERCALL_STANDARD 0
+
+#define TDX_HCALL_HAS_OUTPUT BIT(0)
+#define TDX_HCALL_ISSUE_STI BIT(1)
+
#define TDX_CPUID_LEAF_ID 0x21
#define TDX_IDENT "IntelTDX "

+#ifndef __ASSEMBLY__
+
+/*
+ * Used in __tdx_hypercall() to pass down and get back registers' values of
+ * the TDCALL instruction when requesting services from the VMM.
+ *
+ * This is a software only structure and not part of the TDX module/VMM ABI.
+ */
+struct tdx_hypercall_args {
+ u64 r10;
+ u64 r11;
+ u64 r12;
+ u64 r13;
+ u64 r14;
+ u64 r15;
+};
+
+/* Used to request services from the VMM */
+u64 __tdx_hypercall(struct tdx_hypercall_args *args, unsigned long flags);
+
+#endif /* !__ASSEMBLY__ */
#endif /* _ASM_X86_SHARED_TDX_H */
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 119283d6ce26..1093a5e5f446 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -3,16 +3,10 @@
#ifndef _ASM_X86_TDX_H
#define _ASM_X86_TDX_H

-#include <linux/bits.h>
#include <linux/init.h>
#include <asm/ptrace.h>
#include <asm/shared/tdx.h>

-#define TDX_HYPERCALL_STANDARD 0
-
-#define TDX_HCALL_HAS_OUTPUT BIT(0)
-#define TDX_HCALL_ISSUE_STI BIT(1)
-
/*
* SW-defined error codes.
*
@@ -40,21 +34,6 @@ struct tdx_module_output {
u64 r11;
};

-/*
- * Used in __tdx_hypercall() to pass down and get back registers' values of
- * the TDCALL instruction when requesting services from the VMM.
- *
- * This is a software only structure and not part of the TDX module/VMM ABI.
- */
-struct tdx_hypercall_args {
- u64 r10;
- u64 r11;
- u64 r12;
- u64 r13;
- u64 r14;
- u64 r15;
-};
-
/*
* Used by the #VE exception handler to gather the #VE exception
* info from the TDX module. This is a software only structure
@@ -79,9 +58,6 @@ void __init tdx_early_init(void);
u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
struct tdx_module_output *out);

-/* Used to request services from the VMM */
-u64 __tdx_hypercall(struct tdx_hypercall_args *args, unsigned long flags);
-
void tdx_get_ve_info(struct ve_info *ve);

bool tdx_handle_virt_exception(struct pt_regs *regs, struct ve_info *ve);
--
2.34.1