From e6b28ec65b6d433624a2c290073bc356c4fce914 Mon Sep 17 00:00:00 2001
From: Dmitry Safonov <dima@arista.com>
Date: Tue, 12 Nov 2019 01:27:14 +0000
Subject: [PATCH 25/34] x86/vdso: On timens page fault prefault also VVAR page
Git-commit: e6b28ec65b6d433624a2c290073bc356c4fce914
Patch-mainline: v5.6-rc1
References: bsc#1164648,jsc#SLE-11493

As timens page has offsets to data on VVAR page VVAR is going
to be accessed shortly. Set it up with timens in one page fault
as optimization.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Co-developed-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20191112012724.250792-26-dima@arista.com
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

---
 arch/x86/entry/vdso/vma.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index e5f336112cb1..d2fd8a57af7d 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -170,8 +170,23 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 		 * offset.
 		 * See also the comment near timens_setup_vdso_data().
 		 */
-		if (timens_page)
+		if (timens_page) {
+			unsigned long addr;
+			vm_fault_t err;
+
+			/*
+			 * Optimization: inside time namespace pre-fault
+			 * VVAR page too. As on timens page there are only
+			 * offsets for clocks on VVAR, it'll be faulted
+			 * shortly by VDSO code.
+			 */
+			addr = vmf->address + (image->sym_timens_page - sym_offset);
+			err = vmf_insert_pfn(vma, addr, pfn);
+			if (unlikely(err & VM_FAULT_ERROR))
+				return err;
+
 			pfn = page_to_pfn(timens_page);
+		}
 
 		return vmf_insert_pfn(vma, vmf->address, pfn);
 	} else if (sym_offset == image->sym_pvclock_page) {
-- 
2.16.4