linux-kernel - [PATCH 02/10] x86/tdx: Use cmovc to save a label in TDX_MODULE

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Message-ID: <70784afc0a42d4dc1b1e743f90d89f7728496add.1689151537.git.kai.huang@intel.com>
Date:   Wed, 12 Jul 2023 20:55:16 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     peterz@...radead.org, kirill.shutemov@...ux.intel.com,
        linux-kernel@...r.kernel.org
Cc:     dave.hansen@...el.com, tglx@...utronix.de, bp@...en8.de,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org, seanjc@...gle.com,
        pbonzini@...hat.com, kvm@...r.kernel.org, isaku.yamahata@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, kai.huang@...el.com
Subject: [PATCH 02/10] x86/tdx: Use cmovc to save a label in TDX_MODULE_CALL asm

Change 'jnc .Lno_vmfailinvalid' to 'cmovc %rdi, %rax' to save the
.Lno_vmfailinvalid label in the TDX_MODULE_CALL asm macro.

Note %rdi, which is used as the first argument, has been saved to %rax
as TDCALL leaf ID thus is free to hold the error code for cmovc.

This is basically based on Peter's code.

Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Kai Huang <kai.huang@...el.com>
---
 arch/x86/virt/vmx/tdx/tdxcall.S | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
index 49a54356ae99..3524915d8bd9 100644
--- a/arch/x86/virt/vmx/tdx/tdxcall.S
+++ b/arch/x86/virt/vmx/tdx/tdxcall.S
@@ -57,10 +57,8 @@
 	 * This value will never be used as actual SEAMCALL error code as
 	 * it is from the Reserved status code class.
 	 */
-	jnc .Lno_vmfailinvalid
-	mov $TDX_SEAMCALL_VMFAILINVALID, %rax
-.Lno_vmfailinvalid:
-
+	mov $TDX_SEAMCALL_VMFAILINVALID, %rdi
+	cmovc %rdi, %rax
 	.else
 	tdcall
 	.endif
-- 
2.41.0