linux-kernel - [PATCH 5/6] x86/compressed: adhere to calling convention in get_sev_encryption

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Message-Id: <20220815134223.740112-6-ardb@kernel.org>
Date:   Mon, 15 Aug 2022 15:42:22 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-efi@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Michael Roth <michael.roth@....com>
Subject: [PATCH 5/6] x86/compressed: adhere to calling convention in get_sev_encryption_bit()

Make get_sev_encryption_bit() follow the ordinary x86 calling
convention, and only call it if CONFIG_AMD_MEM_ENCRYPT is actually
enabled. This clarifies the calling code, and makes it more
maintainable.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/boot/compressed/head_64.S     |  6 ++++--
 arch/x86/boot/compressed/mem_encrypt.S | 10 ----------
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 382ed3d8b26a..4539e7c6d4c3 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -180,12 +180,12 @@ SYM_FUNC_START(startup_32)
   */
 	/*
 	 * If SEV is active then set the encryption mask in the page tables.
-	 * This will insure that when the kernel is copied and decompressed
+	 * This will ensure that when the kernel is copied and decompressed
 	 * it will be done so encrypted.
 	 */
+#ifdef CONFIG_AMD_MEM_ENCRYPT
 	call	get_sev_encryption_bit
 	xorl	%edx, %edx
-#ifdef	CONFIG_AMD_MEM_ENCRYPT
 	testl	%eax, %eax
 	jz	1f
 	subl	$32, %eax	/* Encryption bit is always above bit 31 */
@@ -199,6 +199,8 @@ SYM_FUNC_START(startup_32)
 	 */
 	movl	$1, rva(sev_status)(%ebp)
 1:
+#else
+	xorl	%edx, %edx
 #endif
 
 	/* Initialize Page tables to 0 */
diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index 3cd3db0da49d..b4a116283bd9 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -21,12 +21,7 @@
 
 	.code32
 SYM_FUNC_START(get_sev_encryption_bit)
-	xor	%eax, %eax
-
-#ifdef CONFIG_AMD_MEM_ENCRYPT
 	push	%ebx
-	push	%ecx
-	push	%edx
 
 	movl	$0x80000000, %eax	/* CPUID to check the highest leaf */
 	cpuid
@@ -57,12 +52,7 @@ SYM_FUNC_START(get_sev_encryption_bit)
 	xor	%eax, %eax
 
 .Lsev_exit:
-	pop	%edx
-	pop	%ecx
 	pop	%ebx
-
-#endif	/* CONFIG_AMD_MEM_ENCRYPT */
-
 	RET
 SYM_FUNC_END(get_sev_encryption_bit)
 
-- 
2.35.1