linux-kernel - [PATCH 06/11] x86/virt/guest/xen: Remove use of pgd

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Date:	Tue, 22 Sep 2015 08:23:36 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Waiman Long <waiman.long@...com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 06/11] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code

xen_mm_pin_all()/unpin_all() are used to implement full guest instance
suspend/restore. It's a stop-all method that needs to iterate through
all allocated pgds in the system to fix them up for Xen's use.

This code uses pgd_list, probably because it was an easy interface.

But we want to remove the pgd_list, so convert the code over to walk
all tasks in the system. This is an equivalent method.

(As I don't use Xen this is was only build tested.)

Reviewed-by: David Vrabel <david.vrabel@...rix.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Waiman Long <Waiman.Long@...com>
Cc: linux-mm@...ck.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/xen/mmu.c | 45 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 39 insertions(+), 6 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 9c479fe40459..96bb4a7a626d 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -45,6 +45,7 @@
 #include <linux/vmalloc.h>
 #include <linux/module.h>
 #include <linux/gfp.h>
+#include <linux/oom.h>
 #include <linux/memblock.h>
 #include <linux/seq_file.h>
 #include <linux/crash_dump.h>
@@ -854,18 +855,34 @@ static void xen_pgd_pin(struct mm_struct *mm)
  */
 void xen_mm_pin_all(void)
 {
-	struct page *page;
+	struct task_struct *g;
 
+	rcu_read_lock(); /* Task list walk */
 	spin_lock(&pgd_lock);
 
-	list_for_each_entry(page, &pgd_list, lru) {
+	for_each_process(g) {
+		struct task_struct *p;
+		struct mm_struct *mm;
+		struct page *page;
+		pgd_t *pgd;
+
+		p = find_lock_task_mm(g);
+		if (!p)
+			continue;
+
+		mm = p->mm;
+		pgd = mm->pgd;
+		page = virt_to_page(pgd);
+
 		if (!PagePinned(page)) {
-			__xen_pgd_pin(&init_mm, (pgd_t *)page_address(page));
+			__xen_pgd_pin(&init_mm, pgd);
 			SetPageSavePinned(page);
 		}
+		task_unlock(p);
 	}
 
 	spin_unlock(&pgd_lock);
+	rcu_read_unlock();
 }
 
 /*
@@ -968,19 +985,35 @@ static void xen_pgd_unpin(struct mm_struct *mm)
  */
 void xen_mm_unpin_all(void)
 {
-	struct page *page;
+	struct task_struct *g;
 
+	rcu_read_lock(); /* Task list walk */
 	spin_lock(&pgd_lock);
 
-	list_for_each_entry(page, &pgd_list, lru) {
+	for_each_process(g) {
+		struct task_struct *p;
+		struct mm_struct *mm;
+		struct page *page;
+		pgd_t *pgd;
+
+		p = find_lock_task_mm(g);
+		if (!p)
+			continue;
+
+		mm = p->mm;
+		pgd = mm->pgd;
+		page = virt_to_page(pgd);
+
 		if (PageSavePinned(page)) {
 			BUG_ON(!PagePinned(page));
-			__xen_pgd_unpin(&init_mm, (pgd_t *)page_address(page));
+			__xen_pgd_unpin(&init_mm, pgd);
 			ClearPageSavePinned(page);
 		}
+		task_unlock(p);
 	}
 
 	spin_unlock(&pgd_lock);
+	rcu_read_unlock();
 }
 
 static void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
-- 
2.1.4

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