Thread (36 messages) 36 messages, 8 authors, 2023-02-01
STALE1224d

[PATCH 2/2] vhost: check for pending livepatches from vhost worker kthreads

From: Seth Forshee (DigitalOcean) <hidden>
Date: 2023-01-20 22:12:49
Also in: kvm, live-patching, lkml
Subsystem: the rest, virtio host (vhost) · Maintainers: Linus Torvalds, "Michael S. Tsirkin", Jason Wang

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@kernel.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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