linux-kernel - [PATCH 3/3] x86/boot/compressed: Support TDX guest port I/O at decompression time

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Date:   Thu, 20 Jan 2022 05:15:44 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     bp@...en8.de
Cc:     aarcange@...hat.com, ak@...ux.intel.com, dan.j.williams@...el.com,
        dave.hansen@...el.com, david@...hat.com, hpa@...or.com,
        jgross@...e.com, jmattson@...gle.com, joro@...tes.org,
        jpoimboe@...hat.com, kirill.shutemov@...ux.intel.com,
        kirill@...temov.name, knsathya@...nel.org,
        linux-kernel@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        pbonzini@...hat.com, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, sdeep@...are.com,
        seanjc@...gle.com, tglx@...utronix.de, tony.luck@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, x86@...nel.org
Subject: [PATCH 3/3] x86/boot/compressed: Support TDX guest port I/O at decompression time

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@...ux.intel.com>
---
 arch/x86/boot/compressed/Makefile |  2 +-
 arch/x86/boot/compressed/tdcall.S |  3 ++
 arch/x86/boot/compressed/tdx.c    | 62 +++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/boot/compressed/tdcall.S

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 22a2a6cc2ab4..3215442d8d2d 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -98,7 +98,7 @@ 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 ae8c57ea00d8..265359131b92 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -5,6 +5,11 @@
 
 #include "../cpuflags.h"
 #include "../string.h"
+#include "../io.h"
+
+#include <vdso/limits.h>
+#include <uapi/asm/vmx.h>
+#include <asm/tdx.h>
 
 #define TDX_CPUID_LEAF_ID	0x21
 #define TDX_IDENT		"IntelTDX    "
@@ -16,6 +21,54 @@ 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];
@@ -27,4 +80,13 @@ void early_tdx_detect(void)
 
 	/* Cache TDX guest feature status */
 	tdx_guest_detected = true;
+
+	pio_ops = (struct port_io_ops) {
+		.inb = tdx_inb,
+		.inw = tdx_inw,
+		.inl = tdx_inl,
+		.outb = tdx_outb,
+		.outw = tdx_outw,
+		.outl = tdx_outl,
+	};
 }
-- 
2.34.1