linux-kernel - [PATCH 3/3] x86/hyperv: Remove ASM_CALL

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Message-ID: <20251120134105.189753-3-ubizjak@gmail.com>
Date: Thu, 20 Nov 2025 14:40:24 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: linux-hyperv@...r.kernel.org,
	x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 3/3] x86/hyperv: Remove ASM_CALL_CONSTRAINT with VMMCALL insn

Unlike CALL instruction, VMMCALL does not push to the stack, and may be
inserted before the frame pointer gets set up by the containing function.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
Cc: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: Wei Liu <wei.liu@...nel.org>
Cc: Dexuan Cui <decui@...rosoft.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
---
 arch/x86/hyperv/ivm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 7365d8f43181..be7fad43a88d 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -392,7 +392,7 @@ u64 hv_snp_hypercall(u64 control, u64 param1, u64 param2)
 
 	register u64 __r8 asm("r8") = param2;
 	asm volatile("vmmcall"
-		     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+		     : "=a" (hv_status),
 		       "+c" (control), "+d" (param1), "+r" (__r8)
 		     : : "cc", "memory", "r9", "r10", "r11");
 
-- 
2.51.1