diff mbox series

[1/4] x86/tdx: Expand __tdx_hypercall() to handle more arguments

Message ID 20221209132524.20200-2-kirill.shutemov@linux.intel.com
State New
Headers
Series x86/tdx: Changes for TDX guest initialization |

Commit Message

Kirill A. Shutemov Dec. 9, 2022, 1:25 p.m. UTC 
  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(-)

Comments

Dave Hansen Dec. 13, 2022, 10:44 p.m. UTC | #1 
On 12/9/22 05:25, Kirill A. Shutemov wrote:
> So far __tdx_hypercall() only handles six arguments for VMCALL.
> Expanding it to six more register would allow to cover more use-cases.

like...

> 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.

This isn't the world's largest patch, but it doing at least three or
four different logical things.  Ideally, you'd do the restructuring in a
couple of patches and then the last one would just add the six new
registers.

Could you take 20 minutes and see if you can break this down into three
or four patches?

It looks _ok_.  I'd almost ack it as-is, but it should be pretty simple
to break down.
diff mbox series

Patch

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);