[PATCHv2 12/29] x86/boot/compressed: Support TDX guest port I/O at decompression time

Kirill A. Shutemov
2022-01-24T15:03:38Z

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>
---
arch/x86/boot/compressed/Makefile | 2 +-
arch/x86/boot/compressed/tdcall.S | 3 ++
arch/x86/boot/compressed/tdx.c | 59 +++++++++++++++++++++++++++++++
arch/x86/include/asm/shared/tdx.h | 23 ++++++++++++
arch/x86/include/asm/tdx.h | 21 -----------
5 files changed, 86 insertions(+), 22 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..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 6853376fe69a..f2e1449c74cd 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -5,6 +5,10 @@

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

#include <asm/shared/tdx.h>

@@ -15,6 +19,54 @@ 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];
@@ -26,4 +78,11 @@ void early_tdx_detect(void)

/* Cache TDX guest feature status */
tdx_guest_detected = true;
+
+ pio_ops.inb = tdx_inb;
+ pio_ops.inw = tdx_inw;
+ pio_ops.inl = tdx_inl;
+ pio_ops.outb = tdx_outb;
+ pio_ops.outw = tdx_outw;
+ pio_ops.outl = tdx_outl;
}
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 12bede46d048..4a0218bedc75 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -1,7 +1,30 @@
#ifndef _ASM_X86_SHARED_TDX_H
#define _ASM_X86_SHARED_TDX_H

+#include <linux/types.h>
+
+/*
+ * Used in __tdx_hypercall() to gather the output 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_output {
+ u64 r10;
+ u64 r11;
+ u64 r12;
+ u64 r13;
+ u64 r14;
+ u64 r15;
+};
+
+#define TDX_HYPERCALL_STANDARD 0
+
#define TDX_CPUID_LEAF_ID 0x21
#define TDX_IDENT "IntelTDX "

+/* Used to request services from the VMM */
+u64 __tdx_hypercall(u64 type, u64 fn, u64 r12, u64 r13, u64 r14,
+ u64 r15, struct tdx_hypercall_output *out);
+
#endif
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 53f7dd0fbe58..27eb4ab2fdd2 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -7,8 +7,6 @@
#include <asm/ptrace.h>
#include <asm/shared/tdx.h>

-#define TDX_HYPERCALL_STANDARD 0
-
/*
* Used in __tdx_module_call() to gather the output registers'
* values of the TDCALL instruction when requesting services from
@@ -24,21 +22,6 @@ struct tdx_module_output {
u64 r11;
};

-/*
- * Used in __tdx_hypercall() to gather the output 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_output {
- 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
@@ -64,10 +47,6 @@ bool is_tdx_guest(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(u64 type, u64 fn, u64 r12, u64 r13, u64 r14,
- u64 r15, struct tdx_hypercall_output *out);
-
bool tdx_get_ve_info(struct ve_info *ve);

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