linux-kernel - [PATCH] x86/head/64: level2_kernel_pgt's kernel area is built with _PAGE

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Date: Sat, 23 Mar 2024 23:26:21 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com
Cc: x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Wei Yang <richard.weiyang@...il.com>,
	Vivek Goyal <vgoyal@...ibm.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>,
	Steve Wahl <steve.wahl@....com>,
	Borislav Petkov <bp@...e.de>
Subject: [PATCH] x86/head/64: level2_kernel_pgt's kernel area is built with _PAGE_PRESENT set

The code is first introduced in 'commit 1ab60e0f72f7 ("[PATCH] x86-64:
Relocatable Kernel Support")'.  Then 'commit c88d71508e36b
("x86/boot/64: Rewrite startup_64() in C")', convert it to c. And
'commit 2aa85f246c181 ("x86/boot/64: Make level2_kernel_pgt pages
invalid outside kernel area")' limit the range from _text to _end.

Originally, it does the check because the loop iterate the whole
level2_kernel_pgt, while currently it just fixup the kernel area. This
area is built with _PAGE_PRESENT set.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
CC: Vivek Goyal <vgoyal@...ibm.com>
CC: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
CC: Ingo Molnar <mingo@...nel.org>
CC: Steve Wahl <steve.wahl@....com>
CC: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/head64.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 212e8e06aeba..75c69f8620d8 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -253,8 +253,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
 
 	/* fixup pages that are part of the kernel image */
 	for (; i <= pmd_index((unsigned long)_end); i++)
-		if (pmd[i] & _PAGE_PRESENT)
-			pmd[i] += load_delta;
+		pmd[i] += load_delta;
 
 	/* invalidate pages after the kernel image */
 	for (; i < PTRS_PER_PMD; i++)
-- 
2.34.1