Re: Intermittent storage (dm-crypt?) freeze - regression 6.4->6.5

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Thu, Nov 02, 2023 at 06:06:33PM +0100, Mikulas Patocka wrote:
> 
> 
> On Thu, 2 Nov 2023, Marek Marczykowski-Górecki wrote:
> 
> > On Thu, Nov 02, 2023 at 10:28:57AM +0100, Mikulas Patocka wrote:
> > 
> > > Try lowring /sys/block/nvme0n1/queue/max_sectors_kb to some small value 
> > > (for example 64) and test if it helps.
> > 
> > Yes, this helps too.
> 
> On a plain upstream kernel with no other modifications (and with default 
> max_sectors_kb), set the value /sys/module/nvme/parameters/sgl_threshold 
> to "0" and test it if it deadlocks. Then, set this value to "1" and test 
> it again.

Got deadlock wit both values.

> Revert sgl_threshold back to the default (32768). Boot the kernel with the 
> option "iommu=panic". Reproduce the deadlock and if you get a kernel 
> panic, send us the panic log.

This is a Xen PV, so Linux is not in charge of IOMMU here. And there is
SWIOTLB involved (64MB of it), I'm not sure if for every DMA, but
definitely for some. 

> Then, try this patch (without "iommu=panic"), reproduce the deadlock and 
> tell us which one of the "printk" statements is triggered during the 
> deadlock.

I'll try this next.

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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