Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com, linux-mm@kvack.org,
	Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
	Minchan Kim <minchan@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Mohamed Alzayat <alzayat@mpi-sws.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Nadav Amit <namit@vmware.com>,
	Andrea Arcangeli <aarcange@redhat.com>
Subject: [PATCH v3 1/6] mm: proc: Invalidate TLB after clearing soft-dirty page state
Date: Wed, 27 Jan 2021 23:53:42 +0000
Message-ID: <20210127235347.1402-2-will@kernel.org> (raw)
In-Reply-To: <20210127235347.1402-1-will@kernel.org>

Since commit 0758cd830494 ("asm-generic/tlb: avoid potential double
flush"), TLB invalidation is elided in tlb_finish_mmu() if no entries
were batched via the tlb_remove_*() functions. Consequently, the
page-table modifications performed by clear_refs_write() in response to
a write to /proc/<pid>/clear_refs do not perform TLB invalidation.
Although this is fine when simply aging the ptes, in the case of
clearing the "soft-dirty" state we can end up with entries where
pte_write() is false, yet a writable mapping remains in the TLB.

Fix this by avoiding the mmu_gather API altogether: managing both the
'tlb_flush_pending' flag on the 'mm_struct' and explicit TLB
invalidation for the sort-dirty path, much like mprotect() does already.

Fixes: 0758cd830494 ("asm-generic/tlb: avoid potential double flush”)
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 fs/proc/task_mmu.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 602e3a52884d..3cec6fbef725 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1210,7 +1210,6 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
 	enum clear_refs_types type;
-	struct mmu_gather tlb;
 	int itype;
 	int rv;
 
@@ -1249,7 +1248,6 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 			goto out_unlock;
 		}
 
-		tlb_gather_mmu(&tlb, mm, 0, -1);
 		if (type == CLEAR_REFS_SOFT_DIRTY) {
 			for (vma = mm->mmap; vma; vma = vma->vm_next) {
 				if (!(vma->vm_flags & VM_SOFTDIRTY))
@@ -1258,15 +1256,18 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 				vma_set_page_prot(vma);
 			}
 
+			inc_tlb_flush_pending(mm);
 			mmu_notifier_range_init(&range, MMU_NOTIFY_SOFT_DIRTY,
 						0, NULL, mm, 0, -1UL);
 			mmu_notifier_invalidate_range_start(&range);
 		}
 		walk_page_range(mm, 0, mm->highest_vm_end, &clear_refs_walk_ops,
 				&cp);
-		if (type == CLEAR_REFS_SOFT_DIRTY)
+		if (type == CLEAR_REFS_SOFT_DIRTY) {
 			mmu_notifier_invalidate_range_end(&range);
-		tlb_finish_mmu(&tlb, 0, -1);
+			flush_tlb_mm(mm);
+			dec_tlb_flush_pending(mm);
+		}
 out_unlock:
 		mmap_write_unlock(mm);
 out_mm:
-- 
2.30.0.365.g02bc693789-goog



  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-27 23:53 [PATCH v3 0/6] tlb: Fix (soft-)dirty bit management & clean up API Will Deacon
2021-01-27 23:53 ` Will Deacon [this message]
2021-01-27 23:53 ` [PATCH v3 2/6] tlb: mmu_gather: Remove unused start/end arguments from tlb_finish_mmu() Will Deacon
2021-01-27 23:53 ` [PATCH v3 3/6] tlb: mmu_gather: Introduce tlb_gather_mmu_fullmm() Will Deacon
2021-01-27 23:53 ` [PATCH v3 4/6] tlb: mmu_gather: Remove start/end arguments from tlb_gather_mmu() Will Deacon
2021-01-27 23:53 ` [PATCH v3 5/6] tlb: arch: Remove empty __tlb_remove_tlb_entry() stubs Will Deacon
2021-01-27 23:53 ` [PATCH v3 6/6] x86/ldt: Use tlb_gather_mmu_fullmm() when freeing LDT page-tables Will Deacon
2021-01-28 17:14 ` [PATCH v3 0/6] tlb: Fix (soft-)dirty bit management & clean up API Linus Torvalds
2021-01-29 11:09   ` Peter Zijlstra

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210127235347.1402-2-will@kernel.org \
    --to=will@kernel.org \
    --cc=aarcange@redhat.com \
    --cc=alzayat@mpi-sws.org \
    --cc=aneesh.kumar@linux.ibm.com \
    --cc=kernel-team@android.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=minchan@kernel.org \
    --cc=namit@vmware.com \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=vbabka@suse.cz \
    --cc=yuzhao@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git