x86/tdx: Expand __tdx_hypercall() to handle more arguments

So far __tdx_hypercall() only handles six arguments for VMCALL.
Expanding it to six more register would allow to cover more use-cases
like ReportFatalError() and Hyper-V hypercalls.

With all preparations in place, the expansion is pretty straight
forward.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20230126221159.8635-5-kirill.shutemov%40linux.intel.com

arch/x86/coco/tdx/tdcall.S

@@ -13,6 +13,12 @@
 /*
  * Bitmasks of exposed registers (with VMM).
  */
+#define TDX_RDX		BIT(2)
+#define TDX_RBX		BIT(3)
+#define TDX_RSI		BIT(6)
+#define TDX_RDI		BIT(7)
+#define TDX_R8		BIT(8)
+#define TDX_R9		BIT(9)
 #define TDX_R10		BIT(10)
 #define TDX_R11		BIT(11)
 #define TDX_R12		BIT(12)
@@ -27,9 +33,9 @@
  * details can be found in TDX GHCI specification, section
  * titled "TDCALL [TDG.VP.VMCALL] leaf".
  */
-#define TDVMCALL_EXPOSE_REGS_MASK	( TDX_R10 | TDX_R11 | \
-					  TDX_R12 | TDX_R13 | \
-					  TDX_R14 | TDX_R15 )
+#define TDVMCALL_EXPOSE_REGS_MASK	\
+	( TDX_RDX | TDX_RBX | TDX_RSI | TDX_RDI | TDX_R8  | TDX_R9  | \
+	  TDX_R10 | TDX_R11 | TDX_R12 | TDX_R13 | TDX_R14 | TDX_R15 )
 
 /*
  * __tdx_module_call()  - Used by TDX guests to request services from
@@ -124,6 +130,7 @@ SYM_FUNC_START(__tdx_hypercall)
 	push %r14
 	push %r13
 	push %r12
+	push %rbx
 	push %rbp
 
 	/* Free RDI and RSI to be used as TDVMCALL arguments */
@@ -131,12 +138,18 @@ SYM_FUNC_START(__tdx_hypercall)
 	movq %rsi, %rbp
 
 	/* Copy hypercall registers from arg struct: */
+	movq TDX_HYPERCALL_r8(%rax),  %r8
+	movq TDX_HYPERCALL_r9(%rax),  %r9
 	movq TDX_HYPERCALL_r10(%rax), %r10
 	movq TDX_HYPERCALL_r11(%rax), %r11
 	movq TDX_HYPERCALL_r12(%rax), %r12
 	movq TDX_HYPERCALL_r13(%rax), %r13
 	movq TDX_HYPERCALL_r14(%rax), %r14
 	movq TDX_HYPERCALL_r15(%rax), %r15
+	movq TDX_HYPERCALL_rdi(%rax), %rdi
+	movq TDX_HYPERCALL_rsi(%rax), %rsi
+	movq TDX_HYPERCALL_rbx(%rax), %rbx
+	movq TDX_HYPERCALL_rdx(%rax), %rdx
 
 	push %rax
 
@@ -178,12 +191,18 @@ SYM_FUNC_START(__tdx_hypercall)
 	testq $TDX_HCALL_HAS_OUTPUT, %rbp
 	jz .Lout
 
+	movq %r8,  TDX_HYPERCALL_r8(%rax)
+	movq %r9,  TDX_HYPERCALL_r9(%rax)
 	movq %r10, TDX_HYPERCALL_r10(%rax)
 	movq %r11, TDX_HYPERCALL_r11(%rax)
 	movq %r12, TDX_HYPERCALL_r12(%rax)
 	movq %r13, TDX_HYPERCALL_r13(%rax)
 	movq %r14, TDX_HYPERCALL_r14(%rax)
 	movq %r15, TDX_HYPERCALL_r15(%rax)
+	movq %rdi, TDX_HYPERCALL_rdi(%rax)
+	movq %rsi, TDX_HYPERCALL_rsi(%rax)
+	movq %rbx, TDX_HYPERCALL_rbx(%rax)
+	movq %rdx, TDX_HYPERCALL_rdx(%rax)
 .Lout:
 	/* TDVMCALL leaf return code is in R10 */
 	movq %r10, %rax
@@ -191,14 +210,20 @@ SYM_FUNC_START(__tdx_hypercall)
 	/*
 	 * Zero out registers exposed to the VMM to avoid speculative execution
 	 * with VMM-controlled values. This needs to include all registers
-	 * present in TDVMCALL_EXPOSE_REGS_MASK (except R12-R15). R12-R15
-	 * context will be restored.
+	 * present in TDVMCALL_EXPOSE_REGS_MASK, except RBX, and R12-R15 which
+	 * will be restored.
 	 */
+	xor %r8d,  %r8d
+	xor %r9d,  %r9d
 	xor %r10d, %r10d
 	xor %r11d, %r11d
+	xor %rdi,  %rdi
+	xor %rsi,  %rsi
+	xor %rdx,  %rdx
 
 	/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
 	pop %rbp
+	pop %rbx
 	pop %r12
 	pop %r13
 	pop %r14