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Message-Id: <20230120-vhost-klp-switching-v1-2-7c2b65519c43@kernel.org>
Date: Fri, 20 Jan 2023 16:12:22 -0600
From: "Seth Forshee (DigitalOcean)" <sforshee@...italocean.com>
To: Petr Mladek <pmladek@...e.com>, Jason Wang <jasowang@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Miroslav Benes <mbenes@...e.cz>,
Joe Lawrence <joe.lawrence@...hat.com>,
Josh Poimboeuf <jpoimboe@...nel.org>
Cc: virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
"Seth Forshee (DigitalOcean)" <sforshee@...nel.org>,
netdev@...r.kernel.org, live-patching@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] vhost: check for pending livepatches from vhost worker
kthreads
Livepatch relies on stack checking of sleeping tasks to switch kthreads,
so a busy kthread can block a livepatch transition indefinitely. We've
seen this happen fairly often with busy vhost kthreads.
Add a check to call klp_switch_current() from vhost_worker() when a
livepatch is pending. In testing this allowed vhost kthreads to switch
immediately when they had previously blocked livepatch transitions for
long periods of time.
Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@...nel.org>
---
drivers/vhost/vhost.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index cbe72bfd2f1f..d8624f1f2d64 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -30,6 +30,7 @@
#include <linux/interval_tree_generic.h>
#include <linux/nospec.h>
#include <linux/kcov.h>
+#include <linux/livepatch.h>
#include "vhost.h"
@@ -366,6 +367,9 @@ static int vhost_worker(void *data)
if (need_resched())
schedule();
}
+
+ if (unlikely(klp_patch_pending(current)))
+ klp_switch_current();
}
kthread_unuse_mm(dev->mm);
return 0;
--
b4 0.10.1
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