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[drm] *ERROR* (...) pipe state doesn't match! WARNING: CPU: (...) drivers/gpu/drm/i915/display/intel_display.c (...) intel_atomic_commit_tail #176
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aljazzair
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Issue disappeared after reverting to earlier kernel in the guest (5.4) |
zhenyw
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Sep 13, 2021
Currently, if bpf_get_current_cgroup_id() or
bpf_get_current_ancestor_cgroup_id() helper is
called with sleepable programs e.g., sleepable
fentry/fmod_ret/fexit/lsm programs, a rcu warning
may appear. For example, if I added the following
hack to test_progs/test_lsm sleepable fentry program
test_sys_setdomainname:
--- a/tools/testing/selftests/bpf/progs/lsm.c
+++ b/tools/testing/selftests/bpf/progs/lsm.c
@@ -168,6 +168,10 @@ int BPF_PROG(test_sys_setdomainname, struct pt_regs *regs)
int buf = 0;
long ret;
+ __u64 cg_id = bpf_get_current_cgroup_id();
+ if (cg_id == 1000)
+ copy_test++;
+
ret = bpf_copy_from_user(&buf, sizeof(buf), ptr);
if (len == -2 && ret == 0 && buf == 1234)
copy_test++;
I will hit the following rcu warning:
include/linux/cgroup.h:481 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by test_progs/260:
#0: ffffffffa5173360 (rcu_read_lock_trace){....}-{0:0}, at: __bpf_prog_enter_sleepable+0x0/0xa0
stack backtrace:
CPU: 1 PID: 260 Comm: test_progs Tainted: G O 5.14.0-rc2+ #176
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
dump_stack_lvl+0x56/0x7b
bpf_get_current_cgroup_id+0x9c/0xb1
bpf_prog_a29888d1c6706e09_test_sys_setdomainname+0x3e/0x89c
bpf_trampoline_6442469132_0+0x2d/0x1000
__x64_sys_setdomainname+0x5/0x110
do_syscall_64+0x3a/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
I can get similar warning using bpf_get_current_ancestor_cgroup_id() helper.
syzbot reported a similar issue in [1] for syscall program. Helper
bpf_get_current_cgroup_id() or bpf_get_current_ancestor_cgroup_id()
has the following callchain:
task_dfl_cgroup
task_css_set
task_css_set_check
and we have
#define task_css_set_check(task, __c) \
rcu_dereference_check((task)->cgroups, \
lockdep_is_held(&cgroup_mutex) || \
lockdep_is_held(&css_set_lock) || \
((task)->flags & PF_EXITING) || (__c))
Since cgroup_mutex/css_set_lock is not held and the task
is not existing and rcu read_lock is not held, a warning
will be issued. Note that bpf sleepable program is protected by
rcu_read_lock_trace().
The above sleepable bpf programs are already protected
by migrate_disable(). Adding rcu_read_lock() in these
two helpers will silence the above warning.
I marked the patch fixing 95b861a
("bpf: Allow bpf_get_current_ancestor_cgroup_id for tracing")
which added bpf_get_current_ancestor_cgroup_id() to tracing programs
in 5.14. I think backporting 5.14 is probably good enough as sleepable
progrems are not widely used.
This patch should fix [1] as well since syscall program is a sleepable
program protected with migrate_disable().
[1] https://lore.kernel.org/bpf/0000000000006d5cab05c7d9bb87@google.com/
Fixes: 95b861a ("bpf: Allow bpf_get_current_ancestor_cgroup_id for tracing")
Reported-by: syzbot+7ee5c2c09c284495371f@syzkaller.appspotmail.com
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210810230537.2864668-1-yhs@fb.com
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Hello
Fedora Linux guest is spitting errors after a migration to a new host. On the previous host (Centos 8.2 with linux 4.18) no such errors were noticed on the same guest. The new host is Manjaro running more recent Linux kernel (5.8) freshly installed.
The guest is headless; it is used as a Media server. iGPU passthrough provides HW accelerated video encoding/decoding using FFMpeg.
Any pointers on how to address this issue would be most welcome.
Thank you.
Host specs:
Host OS details:
Linux 5.8.18-1-MANJARO #1 SMP PREEMPT Sun Nov 1 14:10:04 UTC 2020 x86_64 GNU/LinuxHost proc/cmdline:
[...] rw quiet splash rhgb nmi_watchdog=0 loglevel=3 vt.global_cursor_default=0 i915.enable_gvt=1 i915.enable_guc=0 biosdevname=0 net.ifnames=0 blacklist=nouveau intel_iommu=on,igfx_off iommu=pt intel_iommu=on,igfx_off vfio-pci.ids=8086:1901,1b21:2142,10de:1b82,10de:10f0,1033:0194 vfio_iommu_type1.allow_unsafe_interrupts=1 transparent_hugepage=never isolcpus=2,8,3,9,4,10,5,11Guest OS Details
Linux 5.9.8-100.fc32.x86_64 #1 SMP Tue Nov 10 22:39:06 UTC 2020 x86_64 x86_64 x86_64 GNU/LinuxVM exerpt from xml:
Expected behavior: no such errors displayed in the guest logs:
Guest OS Details
Linux 5.9.8-100.fc32.x86_64 #1 SMP Tue Nov 10 22:39:06 UTC 2020 x86_64 x86_64 x86_64 GNU/LinuxGuest lspci -vvvs
vainfo
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