linux-kernel - [PATCH] x86/vsyscall/64: Use proper accessor to update p4d entry

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Date:   Mon, 19 Mar 2018 10:31:54 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        luto@...nel.org, x86@...nel.org, jgross@...e.com,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH] x86/vsyscall/64: Use proper accessor to update p4d entry

Writing to it directly does not work for Xen PV guests.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
---
 arch/x86/entry/vsyscall/vsyscall_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 8560ef68a9d6..317be365bce3 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -347,7 +347,7 @@ void __init set_vsyscall_pgtable_user_bits(pgd_t *root)
 	set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));
 	p4d = p4d_offset(pgd, VSYSCALL_ADDR);
 #if CONFIG_PGTABLE_LEVELS >= 5
-	p4d->p4d |= _PAGE_USER;
+	set_p4d(p4d, __p4d(p4d_val(*p4d) | _PAGE_USER));
 #endif
 	pud = pud_offset(p4d, VSYSCALL_ADDR);
 	set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));
-- 
2.14.3