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Message-ID: <c659a328-ff5f-4750-9cbe-b18fc9ffe7e6@linux.intel.com> Date: Wed, 27 Dec 2023 11:11:06 +0800 From: Ethan Zhao <haifeng.zhao@...ux.intel.com> To: bhelgaas@...gle.com, baolu.lu@...ux.intel.com, dwmw2@...radead.org, will@...nel.org, robin.murphy@....com, lukas@...ner.de Cc: linux-pci@...r.kernel.org, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org Subject: Re: [RFC PATCH v8 5/5] iommu/vt-d: don't loop for timeout device-TLB invalidation request forever On 12/27/2023 10:59 AM, Ethan Zhao wrote: > When the device-TLB invalidation (ATS invalidation) 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 Wrong past, please ignore this series. Thanks, Ethan > > --- --- > > (the left part of exception see the hotplug case of ATS capable device) > > If one endpoint device just no response to the device-TLB invalidation > request, but is not gone, it will bring down the whole system, to avoid > such case, don't try the timeout device-TLB request forever. > > and as synchronous program model of current qi_submit_sync() implementation > we couldn't wait for the enough time as PCIe spec said 1min+50%, just break > it in current sync model. (PCIe spec r6.1, sec 10.3.1) > > Signed-off-by: Ethan Zhao <haifeng.zhao@...ux.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 76903a8bf963..206ab0b7294f 100644 > --- a/drivers/iommu/intel/dmar.c > +++ b/drivers/iommu/intel/dmar.c > @@ -1457,7 +1457,7 @@ 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)
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