linux-kernel - [PATCH 12/20] x86/tdx: Rewrite tdx_kvm_hypercall() without __tdx

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Date: Fri, 17 May 2024 17:19:30 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc: linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-hyperv@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 12/20] x86/tdx: Rewrite tdx_kvm_hypercall() without __tdx_hypercall()

tdx_kvm_hypercall() issues KVM hypercall. Rewrite it without using
__tdx_hypercall(). Use tdvmcall_trampoline() instead.

It cuts code bloat substantially:

Function                                     old     new   delta
tdx_kvm_hypercall                            160      53    -107

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/coco/tdx/tdx.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index b7299e668564..e7ffe1cd6d32 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -49,15 +49,15 @@ noinstr void __noreturn __tdx_hypercall_failed(void)
 long tdx_kvm_hypercall(unsigned int nr, unsigned long p1, unsigned long p2,
 		       unsigned long p3, unsigned long p4)
 {
-	struct tdx_module_args args = {
-		.r10 = nr,
-		.r11 = p1,
-		.r12 = p2,
-		.r13 = p3,
-		.r14 = p4,
-	};
+	long ret;
 
-	return __tdx_hypercall(&args);
+	asm("call	tdvmcall_trampoline\n\t"
+	    "movq	%%r10, %0\n\t"
+	    : "=r" (ret)
+	    : "a" (nr), "b" (p1), "D" (p2), "S"(p3), "d"(p4), "c" (0)
+	    : "r12", "r13", "r14", "r15");
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(tdx_kvm_hypercall);
 #endif
-- 
2.43.0