From 86009969c9f59b34de3ce78c173562e4a589cfaa Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Thu, 8 Jun 2017 20:13:40 -0700 Subject: [PATCH] KVM: async_pf: avoid async pf injection when in guest mode MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 9bc1f09f6fa76fdf31eb7d6a4a4df43574725f93 upstream. INFO: task gnome-terminal-:1734 blocked for more than 120 seconds. Not tainted 4.12.0-rc4+ #8 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. gnome-terminal- D 0 1734 1015 0x00000000 Call Trace: __schedule+0x3cd/0xb30 schedule+0x40/0x90 kvm_async_pf_task_wait+0x1cc/0x270 ? __vfs_read+0x37/0x150 ? prepare_to_swait+0x22/0x70 do_async_page_fault+0x77/0xb0 ? do_async_page_fault+0x77/0xb0 async_page_fault+0x28/0x30 This is triggered by running both win7 and win2016 on L1 KVM simultaneously, and then gives stress to memory on L1, I can observed this hang on L1 when at least ~70% swap area is occupied on L0. This is due to async pf was injected to L2 which should be injected to L1, L2 guest starts receiving pagefault w/ bogus %cr2(apf token from the host actually), and L1 guest starts accumulating tasks stuck in D state in kvm_async_pf_task_wait() since missing PAGE_READY async_pfs. This patch fixes the hang by doing async pf when executing L1 guest. Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- Reading git-format-patch failed