Messages in this thread | | | Date | Thu, 11 Jan 2024 10:31:25 +0800 | Subject | Re: [RFC PATCH v10 5/5] iommu/vt-d: don't loop for timeout ATS Invalidation request forever | From | Baolu Lu <> |
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On 1/10/24 4:40 PM, Ethan Zhao wrote: > > On 1/10/2024 1:28 PM, Baolu Lu wrote: >> On 12/29/23 1:05 AM, Ethan Zhao wrote: >>> When the ATS Invalidation request timeout happens, the qi_submit_sync() >>> will restart and loop for the invalidation request forever till it is >>> done, it will block another Invalidation thread such as the fq_timer >>> to issue invalidation request, cause the system lockup as following >>> >>> [exception RIP: native_queued_spin_lock_slowpath+92] >>> >>> RIP: ffffffffa9d1025c RSP: ffffb202f268cdc8 RFLAGS: 00000002 >>> >>> RAX: 0000000000000101 RBX: ffffffffab36c2a0 RCX: 0000000000000000 >>> >>> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffab36c2a0 >>> >>> RBP: ffffffffab36c2a0 R8: 0000000000000001 R9: 0000000000000000 >>> >>> R10: 0000000000000010 R11: 0000000000000018 R12: 0000000000000000 >>> >>> R13: 0000000000000004 R14: ffff9e10d71b1c88 R15: ffff9e10d71b1980 >>> >>> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 >>> >>> (the left part of exception see the hotplug case of ATS capable device) >>> >>> If one endpoint device just no response to the ATS Invalidation request, >>> but is not gone, it will bring down the whole system, to avoid such >>> case, don't try the timeout ATS Invalidation request forever. >>> >>> Signed-off-by: Ethan Zhao <haifeng.zhao@linux.intel.com> >>> --- >>> drivers/iommu/intel/dmar.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c >>> index 0a8d628a42ee..9edb4b44afca 100644 >>> --- a/drivers/iommu/intel/dmar.c >>> +++ b/drivers/iommu/intel/dmar.c >>> @@ -1453,7 +1453,7 @@ int qi_submit_sync(struct intel_iommu *iommu, >>> struct qi_desc *desc, >>> reclaim_free_desc(qi); >>> raw_spin_unlock_irqrestore(&qi->q_lock, flags); >>> - if (rc == -EAGAIN) >>> + if (rc == -EAGAIN && type !=QI_DIOTLB_TYPE && type != >>> QI_DEIOTLB_TYPE) >>> goto restart; >>> if (iotlb_start_ktime) >> >> Above is also unnecessary if qi_check_fault() returns -ETIMEDOUT, >> instead of -EAGAIN. Or did I miss anything? > > It is pro if we fold it into qi_check_fault(), the con is we have to add > > more parameter to qi_check_fault(), no need check invalidation type > > of QI_DIOTLB_TYPE&QI_DEIOTLB_TYPE in qi_check_fault() ?
No need to check the request type as multiple requests might be batched together in a single call. This is also the reason why I asked you to add a flag bit to this helper and make the intention explicit, say,
"This includes requests to interact with a PCI endpoint. The device may become unavailable at any time, so do not attempt to retry if ITE is detected and the device has gone away."
Best regards, baolu
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