[PATCH 13/20] x86/tdx: Rewrite hv_tdx_hypercall() without __tdx_hypercall()

Kirill A. Shutemov
2024-05-17T14:20:01Z

Rewrite hv_tdx_hypercall() in assembly to remove one more
__tdx_hypercall() user.

tdvmcall_trampoline() cannot be used here as Hyper-V uses R8 and RDX to
pass down parameters which is incompatible with tdvmcall_trampoline()

The rewrite cuts code bloat substantially:

Function old new delta
hv_tdx_hypercall 171 42 -129

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/coco/tdx/tdcall.S | 30 ++++++++++++++++++++++++++++++
arch/x86/hyperv/ivm.c | 14 --------------
2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index 269e5789672a..5b60b9c8799f 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -138,3 +138,33 @@ SYM_FUNC_START(tdvmcall_report_fatal_error)

ud2
SYM_FUNC_END(tdvmcall_report_fatal_error)
+
+#ifdef CONFIG_HYPERV
+/*
+ * hv_tdx_hypercall() - Issue Hyper-V hypercall
+ *
+ * RDI - Hypercall ID
+ * RSI - Parameter 1
+ * RCX - Parameter 2
+ */
+SYM_FUNC_START(hv_tdx_hypercall)
+ movq %rdi, %r10
+ movq %rsi, %rdx
+ movq %rcx, %r8
+
+ movq $TDG_VP_VMCALL, %rax
+ movq $(TDX_R8 | TDX_R10 | TDX_RDX), %rcx
+
+ tdcall
+
+ /* TDG.VP.VMCALL never fails on correct use. Panic if it fails. */
+ testq %rax, %rax
+ jnz .Lpanic_hv
+
+ movq %r11, %rax
+
+ RET
+.Lpanic_hv:
+ ud2
+SYM_FUNC_END(hv_tdx_hypercall)
+#endif
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 18d0892d9fc4..562980e19d68 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -401,20 +401,6 @@ static void hv_tdx_msr_read(u64 msr, u64 *val)
if (WARN_ONCE(ret, "Failed to emulate MSR read: %lld\n", ret))
*val = 0;
}
-
-u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
-{
- struct tdx_module_args args = { };
-
- args.r10 = control;
- args.rdx = param1;
- args.r8 = param2;
-
- (void)__tdx_hypercall(&args);
-
- return args.r11;
-}
-
#else
static inline void hv_tdx_msr_write(u64 msr, u64 value) {}
static inline void hv_tdx_msr_read(u64 msr, u64 *value) {}
--
2.43.0