[RFC v2 14/32] x86/tdx: Handle port I/O

[Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>]

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

Unroll string operations and handle port I/O through TDVMCALLs.
Also handle #VE due to I/O operations with the same TDVMCALLs.

Decompression code uses port IO for earlyprintk. We must use
paravirt calls there too if we want to allow earlyprintk.

Decompresion code cannot deal with alternatives: use branches
instead to implement inX() and outX() helpers.

Since we use call instruction in place of in/out instruction,
the argument passed to call instruction has to be in a
register, it cannot be an immediate value like in/out
instruction. So change constraint flag from "Nd" to "d"

Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/boot/compressed/Makefile |   1 +
 arch/x86/boot/compressed/tdcall.S |   9 ++
 arch/x86/include/asm/io.h         |   5 +-
 arch/x86/include/asm/tdx.h        |  46 ++++++++-
 arch/x86/kernel/tdcall.S          | 154 ++++++++++++++++++++++++++++++
 arch/x86/kernel/tdx.c             |  33 +++++++
 6 files changed, 245 insertions(+), 3 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 a2554621cefe..a944a2038797 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -97,6 +97,7 @@ 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/tdcall.S b/arch/x86/boot/compressed/tdcall.S
new file mode 100644
index 000000000000..5ebb80d45ad8
--- /dev/null
+++ b/arch/x86/boot/compressed/tdcall.S
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <asm/export.h>
+
+/* Do not export symbols in decompression code */
+#undef EXPORT_SYMBOL
+#define EXPORT_SYMBOL(sym)
+
+#include "../../kernel/tdcall.S"
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index ef7a686a55a9..30a3b30395ad 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -43,6 +43,7 @@
 #include <asm/page.h>
 #include <asm/early_ioremap.h>
 #include <asm/pgtable_types.h>
+#include <asm/tdx.h>
 
 #define build_mmio_read(name, size, type, reg, barrier) \
 static inline type name(const volatile void __iomem *addr) \
@@ -309,7 +310,7 @@ static inline unsigned type in##bwl##_p(int port)			\
 									\
 static inline void outs##bwl(int port, const void *addr, unsigned long count) \
 {									\
-	if (sev_key_active()) {						\
+	if (sev_key_active() || is_tdx_guest()) {			\
 		unsigned type *value = (unsigned type *)addr;		\
 		while (count) {						\
 			out##bwl(*value, port);				\
@@ -325,7 +326,7 @@ static inline void outs##bwl(int port, const void *addr, unsigned long count) \
 									\
 static inline void ins##bwl(int port, void *addr, unsigned long count)	\
 {									\
-	if (sev_key_active()) {						\
+	if (sev_key_active() || is_tdx_guest()) {			\
 		unsigned type *value = (unsigned type *)addr;		\
 		while (count) {						\
 			*value = in##bwl(port);				\
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index e0b3ed9e262c..b972c6531a53 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -5,6 +5,8 @@
 
 #define TDX_CPUID_LEAF_ID	0x21
 
+#ifndef __ASSEMBLY__
+
 #ifdef CONFIG_INTEL_TDX_GUEST
 
 #include <asm/cpufeature.h>
@@ -67,6 +69,48 @@ long tdx_kvm_hypercall3(unsigned int nr, unsigned long p1, unsigned long p2,
 long tdx_kvm_hypercall4(unsigned int nr, unsigned long p1, unsigned long p2,
 		unsigned long p3, unsigned long p4);
 
+/* Decompression code doesn't know how to handle alternatives */
+#ifdef BOOT_COMPRESSED_MISC_H
+#define __out(bwl, bw)							\
+do {									\
+	if (is_tdx_guest()) {						\
+		asm volatile("call tdg_out" #bwl : :			\
+				"a"(value), "d"(port));			\
+	} else {							\
+		asm volatile("out" #bwl " %" #bw "0, %w1" : :		\
+				"a"(value), "Nd"(port));		\
+	}								\
+} while (0)
+#define __in(bwl, bw)							\
+do {									\
+	if (is_tdx_guest()) {						\
+		asm volatile("call tdg_in" #bwl :			\
+				"=a"(value) : "d"(port));		\
+	} else {							\
+		asm volatile("in" #bwl " %w1, %" #bw "0" :		\
+				"=a"(value) : "Nd"(port));		\
+	}								\
+} while (0)
+#else
+#define __out(bwl, bw)							\
+	alternative_input("out" #bwl " %" #bw "1, %w2",			\
+			"call tdg_out" #bwl, X86_FEATURE_TDX_GUEST,	\
+			"a"(value), "d"(port))
+
+#define __in(bwl, bw)							\
+	alternative_io("in" #bwl " %w2, %" #bw "0",			\
+			"call tdg_in" #bwl, X86_FEATURE_TDX_GUEST,	\
+			"=a"(value), "d"(port))
+#endif
+
+void tdg_outb(unsigned char value, unsigned short port);
+void tdg_outw(unsigned short value, unsigned short port);
+void tdg_outl(unsigned int value, unsigned short port);
+
+unsigned char tdg_inb(unsigned short port);
+unsigned short tdg_inw(unsigned short port);
+unsigned int tdg_inl(unsigned short port);
+
 #else // !CONFIG_INTEL_TDX_GUEST
 
 static inline bool is_tdx_guest(void)
@@ -106,5 +150,5 @@ static inline long tdx_kvm_hypercall4(unsigned int nr, unsigned long p1,
 }
 
 #endif /* CONFIG_INTEL_TDX_GUEST */
-
+#endif /* __ASSEMBLY__ */
 #endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/kernel/tdcall.S b/arch/x86/kernel/tdcall.S
index 964bfd7fc682..df4159bb5103 100644
--- a/arch/x86/kernel/tdcall.S
+++ b/arch/x86/kernel/tdcall.S
@@ -3,6 +3,7 @@
 #include <asm/asm.h>
 #include <asm/frame.h>
 #include <asm/unwind_hints.h>
+#include <asm/export.h>
 
 #include <linux/linkage.h>
 
@@ -12,6 +13,12 @@
  */
 #define TDVMCALL_EXPOSE_REGS_MASK	0xfc00
 #define TDVMCALL_VENDOR_KVM		0x4d564b2e584454 /* "TDX.KVM" */
+#define EXIT_REASON_IO_INSTRUCTION	30
+/*
+ * Current size of struct tdvmcall_output is 40 bytes,
+ * but allocate double to account future changes.
+ */
+#define TDVMCALL_OUTPUT_SIZE		80
 
 /*
  * TDX guests use the TDCALL instruction to make
@@ -205,3 +212,150 @@ SYM_FUNC_START(__tdvmcall_vendor_kvm)
 	call do_tdvmcall
 	retq
 SYM_FUNC_END(__tdvmcall_vendor_kvm)
+
+.macro io_save_registers
+	push %rbp
+	push %rbx
+	push %rcx
+	push %rdx
+	push %rdi
+	push %rsi
+	push %r8
+	push %r9
+	push %r10
+	push %r11
+	push %r12
+	push %r13
+	push %r14
+	push %r15
+.endm
+.macro io_restore_registers
+	pop %r15
+	pop %r14
+	pop %r13
+	pop %r12
+	pop %r11
+	pop %r10
+	pop %r9
+	pop %r8
+	pop %rsi
+	pop %rdi
+	pop %rdx
+	pop %rcx
+	pop %rbx
+	pop %rbp
+.endm
+
+/*
+ * tdg_out{b,w,l}()  - Write given data to the specified port.
+ *
+ * @arg1 (RAX)       - Value to be written (passed via R8 to do_tdvmcall()).
+ * @arg2 (RDX)       - Port id (passed via RCX to do_tdvmcall()).
+ *
+ */
+SYM_FUNC_START(tdg_outb)
+	io_save_registers
+	xor %r8, %r8
+	/* Move data to R8 register */
+	mov %al, %r8b
+	/* Set data width to 1 byte */
+	mov $1, %rsi
+	jmp 1f
+
+SYM_FUNC_START(tdg_outw)
+	io_save_registers
+	xor %r8, %r8
+	/* Move data to R8 register */
+	mov %ax, %r8w
+	/* Set data width to 2 bytes */
+	mov $2, %rsi
+	jmp 1f
+
+SYM_FUNC_START(tdg_outl)
+	io_save_registers
+	xor %r8, %r8
+	/* Move data to R8 register */
+	mov %eax, %r8d
+	/* Set data width to 4 bytes */
+	mov $4, %rsi
+1:
+	/*
+	 * Since io_save_registers does not save rax
+	 * state, save it here so that we can preserve
+	 * the caller register state.
+	 */
+	push %rax
+
+	mov %rdx, %rcx
+	/* Set 1 in RDX to select out operation */
+	mov $1, %rdx
+	/* Set TDVMCALL function id in RDI */
+	mov $EXIT_REASON_IO_INSTRUCTION, %rdi
+	/* Set TDVMCALL type info (0 - Standard, > 0 - vendor) in R10 */
+	xor %r10, %r10
+	/* Since we don't use tdvmcall output, set it to NULL */
+	xor %r9, %r9
+
+	call do_tdvmcall
+
+	pop %rax
+	io_restore_registers
+	ret
+SYM_FUNC_END(tdg_outb)
+SYM_FUNC_END(tdg_outw)
+SYM_FUNC_END(tdg_outl)
+EXPORT_SYMBOL(tdg_outb)
+EXPORT_SYMBOL(tdg_outw)
+EXPORT_SYMBOL(tdg_outl)
+
+/*
+ * tdg_in{b,w,l}()   - Read data to the specified port.
+ *
+ * @arg1 (RDX)       - Port id (passed via RCX to do_tdvmcall()).
+ *
+ * Returns data read via RAX register.
+ *
+ */
+SYM_FUNC_START(tdg_inb)
+	io_save_registers
+	/* Set data width to 1 byte */
+	mov $1, %rsi
+	jmp 1f
+
+SYM_FUNC_START(tdg_inw)
+	io_save_registers
+	/* Set data width to 2 bytes */
+	mov $2, %rsi
+	jmp 1f
+
+SYM_FUNC_START(tdg_inl)
+	io_save_registers
+	/* Set data width to 4 bytes */
+	mov $4, %rsi
+1:
+	mov %rdx, %rcx
+	/* Set 0 in RDX to select in operation */
+	mov $0, %rdx
+	/* Set TDVMCALL function id in RDI */
+	mov $EXIT_REASON_IO_INSTRUCTION, %rdi
+	/* Set TDVMCALL type info (0 - Standard, > 0 - vendor) in R10 */
+	xor %r10, %r10
+	/* Allocate memory in stack for Output */
+	subq $TDVMCALL_OUTPUT_SIZE, %rsp
+	/* Move tdvmcall_output pointer to R9 */
+	movq %rsp, %r9
+
+	call do_tdvmcall
+
+	/* Move data read from port to RAX */
+	mov TDVMCALL_r11(%r9), %eax
+	/* Free allocated memory */
+	addq $TDVMCALL_OUTPUT_SIZE, %rsp
+	io_restore_registers
+	ret
+SYM_FUNC_END(tdg_inb)
+SYM_FUNC_END(tdg_inw)
+SYM_FUNC_END(tdg_inl)
+EXPORT_SYMBOL(tdg_inb)
+EXPORT_SYMBOL(tdg_inw)
+EXPORT_SYMBOL(tdg_inl)
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index e42e260df245..ec61f2f06c98 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -189,6 +189,36 @@ static void tdg_handle_cpuid(struct pt_regs *regs)
 	regs->dx = out.r15;
 }
 
+static void tdg_out(int size, int port, unsigned int value)
+{
+	tdvmcall(EXIT_REASON_IO_INSTRUCTION, size, 1, port, value);
+}
+
+static unsigned int tdg_in(int size, int port)
+{
+	return tdvmcall_out_r11(EXIT_REASON_IO_INSTRUCTION, size, 0, port, 0);
+}
+
+static void tdg_handle_io(struct pt_regs *regs, u32 exit_qual)
+{
+	bool string = exit_qual & 16;
+	int out, size, port;
+
+	/* I/O strings ops are unrolled at build time. */
+	BUG_ON(string);
+
+	out = (exit_qual & 8) ? 0 : 1;
+	size = (exit_qual & 7) + 1;
+	port = exit_qual >> 16;
+
+	if (out) {
+		tdg_out(size, port, regs->ax);
+	} else {
+		regs->ax &= ~GENMASK(8 * size, 0);
+		regs->ax |= tdg_in(size, port) & GENMASK(8 * size, 0);
+	}
+}
+
 unsigned long tdg_get_ve_info(struct ve_info *ve)
 {
 	u64 ret;
@@ -238,6 +268,9 @@ int tdg_handle_virtualization_exception(struct pt_regs *regs,
 	case EXIT_REASON_CPUID:
 		tdg_handle_cpuid(regs);
 		break;
+	case EXIT_REASON_IO_INSTRUCTION:
+		tdg_handle_io(regs, ve->exit_qual);
+		break;
 	default:
 		pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
 		return -EFAULT;
-- 
2.25.1