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Date: Tue, 30 Apr 2024 15:03:23 +0200
From: Borislav Petkov <bp@alien8.de>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>,
	Elena Reshetova <elena.reshetova@intel.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	"Kalra, Ashish" <ashish.kalra@amd.com>,
	Sean Christopherson <seanjc@google.com>,
	"Huang, Kai" <kai.huang@intel.com>, Baoquan He <bhe@redhat.com>,
	kexec@lists.infradead.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCHv10 05/18] x86/kexec: Keep CR4.MCE set during kexec for
 TDX guest
Message-ID: <20240430130323.GAZjDsG00Xdhv5mv8W@fat_crate.local>
References: <20240409113010.465412-1-kirill.shutemov@linux.intel.com>
 <20240409113010.465412-6-kirill.shutemov@linux.intel.com>
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In-Reply-To: <20240409113010.465412-6-kirill.shutemov@linux.intel.com>

On Tue, Apr 09, 2024 at 02:29:57PM +0300, Kirill A. Shutemov wrote:
> +1:
> +	testq	$X86_CR4_MCE, %r13
> +	jz	1f
> +	ALTERNATIVE "", __stringify(orl $X86_CR4_MCE, %eax), X86_FEATURE_TDX_GUEST
>  1:

Please add the below patch to your set. Those same-number labels are
just abominable.

Thx.

---
From: "Borislav Petkov (AMD)" <bp@alien8.de>
Date: Tue, 30 Apr 2024 15:00:16 +0200
Subject: [PATCH] x86/relocate_kernel: Use named labels for less confusion

That identity_mapped() function was loving that "1" label to the point
of completely confusing its readers.

Use named labels in each place for clarity.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/kernel/relocate_kernel_64.S | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 8e2037d78a1f..0077c9e562a7 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -152,13 +152,15 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 	 */
 	movl	$X86_CR4_PAE, %eax
 	testq	$X86_CR4_LA57, %r13
-	jz	1f
+	jz	no_la57
 	orl	$X86_CR4_LA57, %eax
-1:
+no_la57:
+
 	testq	$X86_CR4_MCE, %r13
-	jz	1f
+	jz	mca_off
 	ALTERNATIVE "", __stringify(orl $X86_CR4_MCE, %eax), X86_FEATURE_TDX_GUEST
-1:
+mca_off:
+
 	movq	%rax, %cr4
 
 	jmp 1f
@@ -173,9 +175,9 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 	 * used by kexec. Flush the caches before copying the kernel.
 	 */
 	testq	%r12, %r12
-	jz 1f
+	jz sme_off
 	wbinvd
-1:
+sme_off:
 
 	movq	%rcx, %r11
 	call	swap_pages
@@ -195,7 +197,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 	 */
 
 	testq	%r11, %r11
-	jnz 1f
+	jnz relocate
 	xorl	%eax, %eax
 	xorl	%ebx, %ebx
 	xorl    %ecx, %ecx
@@ -216,7 +218,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 	ret
 	int3
 
-1:
+relocate:
 	popq	%rdx
 	leaq	PAGE_SIZE(%r10), %rsp
 	ANNOTATE_RETPOLINE_SAFE
-- 
2.43.0

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette