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When the > page-fault worker later tries to ack one of these, it calls into > guc_ct_send_locked() on an already-suspended device, tripping: > >   Assertion `!xe_pm_runtime_suspended(xe)` failed! >   WARNING at xe_device.c:1267 xe_device_assert_mem_access+0x11c/0x140 [xe] > > A live VM/exec queue always holds a PM reference while it has > outstanding work, so if the device is suspended at ack time, the > owning context is already gone and the fault is stale. > > Take a runtime PM reference across the entire pagefault > queue worker to safely deliver acks for torn-down VMs. > > v3: > - Move PM ref to the generic xe_pagefault_queue_work using > guard(xe_pm_runtime)(xe) instead of tracking it in the GuC > backend(Matt Brost). > > v2: > - Hold PM ref across the entire batch (begin/end) instead of per-ack. > This prevents the device from autosuspending mid-batch, which would > leave write_only acks written but the end flush skipped, and skip > counter++, desyncing the cadence check.(Himal) > - Add a comment explaining stale faults.(Himal) > > Fixes: f289f7807119 ("drm/xe: Add xe_guc_pagefault layer") > Reported-by: Szymon Markiewicz Reviewed-by: Matthew Brost > Signed-off-by: Varun Gupta > --- > drivers/gpu/drm/xe/xe_pagefault.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/xe/xe_pagefault.c b/drivers/gpu/drm/xe/xe_pagefault.c > index 2e415995f067..3e8e8f7f5f40 100644 > --- a/drivers/gpu/drm/xe/xe_pagefault.c > +++ b/drivers/gpu/drm/xe/xe_pagefault.c > @@ -17,6 +17,7 @@ > #include "xe_log.h" > #include "xe_pagefault.h" > #include "xe_pagefault_types.h" > +#include "xe_pm.h" > #include "xe_svm.h" > #include "xe_trace_bo.h" > #include "xe_vm.h" > @@ -604,6 +605,13 @@ static void xe_pagefault_queue_work(struct work_struct *w) > u64 cache_start = XE_PAGEFAULT_CACHE_START_INVALID, cache_end = 0; > u32 cache_asid = 0; > > + /* > + * A live VM holds a PM reference, but a torn-down VM does not. > + * Guard the entire worker loop to safely drain stale faults and > + * prevent autosuspends from desyncing batched CT flushes. > + */ > + guard(xe_pm_runtime)(xe); > + > #define USM_QUEUE_MAX_RUNTIME_MS 20 > threshold = jiffies + msecs_to_jiffies(USM_QUEUE_MAX_RUNTIME_MS); > > -- > 2.43.0 >