linux-kernel - [tip:x86/urgent] x86/mm: Make set_pmd

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Date:   Sat, 9 Feb 2019 23:52:09 -0800
From:   tip-bot for Juergen Gross <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux@...elenboom.it, jgross@...e.com,
        linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
        tglx@...utronix.de
Subject: [tip:x86/urgent] x86/mm: Make set_pmd_at() paravirt aware

Commit-ID:  20e55bc17dd01f13cec0eb17e76e9511b23963ef
Gitweb:     https://git.kernel.org/tip/20e55bc17dd01f13cec0eb17e76e9511b23963ef
Author:     Juergen Gross <jgross@...e.com>
AuthorDate: Sun, 10 Feb 2019 08:40:56 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sun, 10 Feb 2019 08:47:12 +0100

x86/mm: Make set_pmd_at() paravirt aware

set_pmd_at() calls native_set_pmd() unconditionally on x86. This was
fine as long as only huge page entries were written via set_pmd_at(),
as Xen pv guests don't support those.

Commit 2c91bd4a4e2e53 ("mm: speed up mremap by 20x on large regions")
introduced a usage of set_pmd_at() possible on pv guests, leading to
failures like:

BUG: unable to handle kernel paging request at ffff888023e26778
#PF error: [PROT] [WRITE]
RIP: e030:move_page_tables+0x7c1/0xae0
move_vma.isra.3+0xd1/0x2d0
__se_sys_mremap+0x3c6/0x5b0
 do_syscall_64+0x49/0x100
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Make set_pmd_at() paravirt aware by just letting it use set_pmd().

Fixes: 2c91bd4a4e2e53 ("mm: speed up mremap by 20x on large regions")
Reported-by: Sander Eikelenboom <linux@...elenboom.it>
Signed-off-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: xen-devel@...ts.xenproject.org
Cc: boris.ostrovsky@...cle.com
Cc: sstabellini@...nel.org
Cc: hpa@...or.com
Cc: bp@...en8.de
Cc: torvalds@...ux-foundation.org
Link: https://lkml.kernel.org/r/20190210074056.11842-1-jgross@suse.com

---
 arch/x86/include/asm/pgtable.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 40616e805292..2779ace16d23 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1065,7 +1065,7 @@ static inline void native_set_pte_at(struct mm_struct *mm, unsigned long addr,
 static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 			      pmd_t *pmdp, pmd_t pmd)
 {
-	native_set_pmd(pmdp, pmd);
+	set_pmd(pmdp, pmd);
 }
 
 static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,