Re: [RFC PATCH v8 5/5] iommu/vt-d: don't loop for timeout device-TLB invalidation request forever

[Ethan Zhao <haifeng.zhao@linux.intel.com>]

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@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 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)