linux-kernel - [PATCH] x86/mm: Fix marking of unused sub-pmd ranges

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Date:   Mon,  9 May 2022 11:06:37 +0200
From:   Adrian-Ken Rueegsegger <ken@...elabs.ch>
To:     dave.hansen@...ux.intel.com, osalvador@...e.de
Cc:     david@...hat.com, luto@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Adrian-Ken Rueegsegger <ken@...elabs.ch>
Subject: [PATCH] x86/mm: Fix marking of unused sub-pmd ranges

The unused part precedes the new range spanned by the start, end
parameters of vmemmap_use_new_sub_pmd. This means it actually goes from
ALIGN_DOWN(start, PMD_SIZE) up to start. Use the correct address when
applying the mark using memset.

Fixes: 8d400913c231 ("x86/vmemmap: handle unpopulated sub-pmd ranges")
Signed-off-by: Adrian-Ken Rueegsegger <ken@...elabs.ch>
---
 arch/x86/mm/init_64.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 96d34ebb20a9..e2942335d143 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -902,6 +902,8 @@ static void __meminit vmemmap_use_sub_pmd(unsigned long start, unsigned long end
 
 static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long end)
 {
+	const unsigned long page = ALIGN_DOWN(start, PMD_SIZE);
+
 	vmemmap_flush_unused_pmd();
 
 	/*
@@ -914,8 +916,7 @@ static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long
 	 * Mark with PAGE_UNUSED the unused parts of the new memmap range
 	 */
 	if (!IS_ALIGNED(start, PMD_SIZE))
-		memset((void *)start, PAGE_UNUSED,
-			start - ALIGN_DOWN(start, PMD_SIZE));
+		memset((void *)page, PAGE_UNUSED, start - page);
 
 	/*
 	 * We want to avoid memset(PAGE_UNUSED) when populating the vmemmap of
-- 
2.30.2