[PATCHv8 25/34] x86/vdso: On timens page fault prefault also VVAR page

Dmitry Safonov dima at arista.com
Tue Nov 12 01:27:14 UTC 2019


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 at linutronix.de>
Co-developed-by: Andrei Vagin <avagin at gmail.com>
Signed-off-by: Andrei Vagin <avagin at gmail.com>
Signed-off-by: Dmitry Safonov <dima at arista.com>
---
 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 f6e13ab29d94..d6cb8a16f368 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -169,8 +169,23 @@ 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) {
-- 
2.24.0



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