linux-kernel - [PATCH v2 3/5] x86/pvh: Omit needless clearing of phys

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Message-ID: <20240930071513.909462-10-ardb+git@google.com>
Date: Mon, 30 Sep 2024 09:15:17 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>, Jason Andryuk <jason.andryuk@....com>, 
	Juergen Gross <jgross@...e.com>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, x86@...nel.org, 
	xen-devel@...ts.xenproject.org
Subject: [PATCH v2 3/5] x86/pvh: Omit needless clearing of phys_base

From: Ard Biesheuvel <ardb@...nel.org>

Since commit

  d9ec1158056b ("x86/boot/64: Use RIP_REL_REF() to assign 'phys_base'")

phys_base is assigned directly rather than added to, so it is no longer
necessary to clear it after use.

Reviewed-by: Jason Andryuk <jason.andryuk@....com>
Tested-by: Jason Andryuk <jason.andryuk@....com>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/platform/pvh/head.S | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index 5a196fb3ebd8..7ca51a4da217 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -180,13 +180,6 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 	ANNOTATE_RETPOLINE_SAFE
 	call *%rax
 
-	/*
-	 * Clear phys_base.  __startup_64 will *add* to its value,
-	 * so reset to 0.
-	 */
-	xor  %rbx, %rbx
-	movq %rbx, phys_base(%rip)
-
 	/* startup_64 expects boot_params in %rsi. */
 	lea pvh_bootparams(%rip), %rsi
 	jmp startup_64
-- 
2.46.1.824.gd892dcdcdd-goog