From: Uros Bizjak <ubizjak@gmail.com>
Date: Fri, 21 Nov 2025 14:14:11 +0000 (+0100)
Subject: x86/hyperv: Remove ASM_CALL_CONSTRAINT with VMMCALL insn
X-Git-Tag: v7.0-rc1~43^2~13
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=885e78d71f772dd4c83f83530814870062115f85;p=thirdparty%2Fkernel%2Flinux.git

x86/hyperv: Remove ASM_CALL_CONSTRAINT with VMMCALL insn

Unlike CALL instruction, VMMCALL does not push to the stack, so it's
OK to allow the compiler to insert it before the frame pointer gets
set up by the containing function. ASM_CALL_CONSTRAINT is for CALLs
that must be inserted after the frame pointer is set up, so it is
over-constraining here and can be removed.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
---

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");