automatic update

1 files changed, 75 insertions, 0 deletions

diff --git a/disable-per-VMA_v4_2.patch b/disable-per-VMA_v4_2.patch
new file mode 100644
index 000000000000..a86c966a4110
--- /dev/null
+++ b/disable-per-VMA_v4_2.patch
@@ -0,0 +1,75 @@
+From: Suren Baghdasaryan <surenb@google.com>
+To: akpm@linux-foundation.org
+Cc: jirislaby@kernel.org, jacobly.alt@gmail.com,
+	holger@applied-asynchrony.com, hdegoede@redhat.com,
+	michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
+	vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net,
+	dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com,
+	peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org,
+	mingo@redhat.com, will@kernel.org, luto@kernel.org,
+	songliubraving@fb.com, peterx@redhat.com, david@redhat.com,
+	dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de,
+	kent.overstreet@linux.dev, punit.agrawal@bytedance.com,
+	lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com,
+	chriscli@google.com, axelrasmussen@google.com, joelaf@google.com,
+	minchan@google.com, rppt@kernel.org, jannh@google.com,
+	shakeelb@google.com, tatashin@google.com, edumazet@google.com,
+	gthelen@google.com, linux-mm@kvack.org,
+	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
+	Suren Baghdasaryan <surenb@google.com>
+Subject: [PATCH v4 1/2] fork: lock VMAs of the parent process when forking
+Date: Wed,  5 Jul 2023 18:13:59 -0700	[thread overview]
+Message-ID: <20230706011400.2949242-2-surenb@google.com> (raw)
+In-Reply-To: <20230706011400.2949242-1-surenb@google.com>
+
+When forking a child process, parent write-protects an anonymous page
+and COW-shares it with the child being forked using copy_present_pte().
+Parent's TLB is flushed right before we drop the parent's mmap_lock in
+dup_mmap(). If we get a write-fault before that TLB flush in the parent,
+and we end up replacing that anonymous page in the parent process in
+do_wp_page() (because, COW-shared with the child), this might lead to
+some stale writable TLB entries targeting the wrong (old) page.
+Similar issue happened in the past with userfaultfd (see flush_tlb_page()
+call inside do_wp_page()).
+Lock VMAs of the parent process when forking a child, which prevents
+concurrent page faults during fork operation and avoids this issue.
+This fix can potentially regress some fork-heavy workloads. Kernel build
+time did not show noticeable regression on a 56-core machine while a
+stress test mapping 10000 VMAs and forking 5000 times in a tight loop
+shows ~7% regression. If such fork time regression is unacceptable,
+disabling CONFIG_PER_VMA_LOCK should restore its performance. Further
+optimizations are possible if this regression proves to be problematic.
+
+Suggested-by: David Hildenbrand <david@redhat.com>
+Reported-by: Jiri Slaby <jirislaby@kernel.org>
+Closes: https://lore.kernel.org/all/dbdef34c-3a07-5951-e1ae-e9c6e3cdf51b@kernel.org/
+Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
+Closes: https://lore.kernel.org/all/b198d649-f4bf-b971-31d0-e8433ec2a34c@applied-asynchrony.com/
+Reported-by: Jacob Young <jacobly.alt@gmail.com>
+Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217624
+Fixes: 0bff0aaea03e ("x86/mm: try VMA lock-based page fault handling first")
+Cc: stable@vger.kernel.org
+Signed-off-by: Suren Baghdasaryan <surenb@google.com>
+---
+ kernel/fork.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/kernel/fork.c b/kernel/fork.c
+index b85814e614a5..2ba918f83bde 100644
+--- a/kernel/fork.c
++++ b/kernel/fork.c
+@@ -658,6 +658,12 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
+ 		retval = -EINTR;
+ 		goto fail_uprobe_end;
+ 	}
++#ifdef CONFIG_PER_VMA_LOCK
++	/* Disallow any page faults before calling flush_cache_dup_mm */
++	for_each_vma(old_vmi, mpnt)
++		vma_start_write(mpnt);
++	vma_iter_set(&old_vmi, 0);
++#endif
+ 	flush_cache_dup_mm(oldmm);
+ 	uprobe_dup_mmap(oldmm, mm);
+ 	/*
+-- 
+2.41.0.255.g8b1d071c50-goog