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From:   "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To:     Dave Hansen <dave.hansen@intel.com>,
        Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Elena Reshetova <elena.reshetova@intel.com>, x86@kernel.org,
        linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCH 1/4] x86/tdx: Expand __tdx_hypercall() to handle more arguments
Date:   Fri,  9 Dec 2022 16:25:21 +0300
Message-Id: <20221209132524.20200-2-kirill.shutemov@linux.intel.com>
In-Reply-To: <20221209132524.20200-1-kirill.shutemov@linux.intel.com>
References: <20221209132524.20200-1-kirill.shutemov@linux.intel.com>
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So far __tdx_hypercall() only handles six arguments for VMCALL.
Expanding it to six more register would allow to cover more use-cases.

Using RDI and RSI as VMCALL arguments requires more register shuffling.
RAX is used to hold tdx_hypercall_args pointer and RBP stores flags.

While there, fix typo in the comment on panic branch.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/coco/tdx/tdcall.S        | 82 ++++++++++++++++++++++---------
 arch/x86/include/asm/shared/tdx.h |  6 +++
 arch/x86/kernel/asm-offsets.c     |  6 +++
 3 files changed, 70 insertions(+), 24 deletions(-)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index f9eb1134f22d..64e57739dc9d 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/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
@@ -124,19 +130,32 @@ SYM_FUNC_START(__tdx_hypercall)
 	push %r14
 	push %r13
 	push %r12
+	push %rbx
+	push %rbp
+
+	movq %rdi, %rax
+	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
 
 	/* Mangle function call ABI into TDCALL ABI: */
 	/* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */
 	xor %eax, %eax
 
-	/* Copy hypercall registers from arg struct: */
-	movq TDX_HYPERCALL_r10(%rdi), %r10
-	movq TDX_HYPERCALL_r11(%rdi), %r11
-	movq TDX_HYPERCALL_r12(%rdi), %r12
-	movq TDX_HYPERCALL_r13(%rdi), %r13
-	movq TDX_HYPERCALL_r14(%rdi), %r14
-	movq TDX_HYPERCALL_r15(%rdi), %r15
-
 	movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx
 
 	/*
@@ -148,14 +167,14 @@ SYM_FUNC_START(__tdx_hypercall)
 	 * HLT operation indefinitely. Since this is the not the desired
 	 * result, conditionally call STI before TDCALL.
 	 */
-	testq $TDX_HCALL_ISSUE_STI, %rsi
+	testq $TDX_HCALL_ISSUE_STI, %rbp
 	jz .Lskip_sti
 	sti
 .Lskip_sti:
 	tdcall
 
 	/*
-	 * RAX==0 indicates a failure of the TDVMCALL mechanism itself and that
+	 * RAX!=0 indicates a failure of the TDVMCALL mechanism itself and that
 	 * something has gone horribly wrong with the TDX module.
 	 *
 	 * The return status of the hypercall operation is in a separate
@@ -165,30 +184,45 @@ SYM_FUNC_START(__tdx_hypercall)
 	testq %rax, %rax
 	jne .Lpanic
 
-	/* TDVMCALL leaf return code is in R10 */
-	movq %r10, %rax
+	pop %rax
 
 	/* Copy hypercall result registers to arg struct if needed */
-	testq $TDX_HCALL_HAS_OUTPUT, %rsi
+	testq $TDX_HCALL_HAS_OUTPUT, %rbp
 	jz .Lout
 
-	movq %r10, TDX_HYPERCALL_r10(%rdi)
-	movq %r11, TDX_HYPERCALL_r11(%rdi)
-	movq %r12, TDX_HYPERCALL_r12(%rdi)
-	movq %r13, TDX_HYPERCALL_r13(%rdi)
-	movq %r14, TDX_HYPERCALL_r14(%rdi)
-	movq %r15, TDX_HYPERCALL_r15(%rdi)
+	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
+
 	/*
 	 * 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
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index e53f26228fbb..8068faa52de1 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -22,12 +22,18 @@
  * This is a software only structure and not part of the TDX module/VMM ABI.
  */
 struct tdx_hypercall_args {
+	u64 r8;
+	u64 r9;
 	u64 r10;
 	u64 r11;
 	u64 r12;
 	u64 r13;
 	u64 r14;
 	u64 r15;
+	u64 rdi;
+	u64 rsi;
+	u64 rbx;
+	u64 rdx;
 };
 
 /* Used to request services from the VMM */
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index a668a70abf32..3b6957d4d0ed 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -75,12 +75,18 @@ static void __used common(void)
 	OFFSET(TDX_MODULE_r11, tdx_module_output, r11);
 
 	BLANK();
+	OFFSET(TDX_HYPERCALL_r8,  tdx_hypercall_args, r8);
+	OFFSET(TDX_HYPERCALL_r9,  tdx_hypercall_args, r9);
 	OFFSET(TDX_HYPERCALL_r10, tdx_hypercall_args, r10);
 	OFFSET(TDX_HYPERCALL_r11, tdx_hypercall_args, r11);
 	OFFSET(TDX_HYPERCALL_r12, tdx_hypercall_args, r12);
 	OFFSET(TDX_HYPERCALL_r13, tdx_hypercall_args, r13);
 	OFFSET(TDX_HYPERCALL_r14, tdx_hypercall_args, r14);
 	OFFSET(TDX_HYPERCALL_r15, tdx_hypercall_args, r15);
+	OFFSET(TDX_HYPERCALL_rdi, tdx_hypercall_args, rdi);
+	OFFSET(TDX_HYPERCALL_rsi, tdx_hypercall_args, rsi);
+	OFFSET(TDX_HYPERCALL_rbx, tdx_hypercall_args, rbx);
+	OFFSET(TDX_HYPERCALL_rdx, tdx_hypercall_args, rdx);
 
 	BLANK();
 	OFFSET(BP_scratch, boot_params, scratch);
-- 
2.38.0