Hi, On Mon, Oct 24, 2022 at 05:26:44PM +0530, Sreekanth Reddy wrote: > On Sun, Oct 23, 2022 at 6:57 AM Bart Van Assche <bvanassche@xxxxxxx> wrote: > > > > On 10/21/22 02:22, Salvatore Bonaccorso wrote: > > > We got the following report in Debian after an update from 5.10.140 to > > > the current 5.10.149. Full quoting below (from > > > https://bugs.debian.org/1022126). Does this ring some bell about known > > > regressions? > > > > Only three mpt3sas changes are new in v5.10.149 compared to v5.10.140: > > $ git log --format=oneline v5.10.140..v5.10.149 > > 2b9aba0c5d58e141e32bb1bb4c7cd91d19f075b8 scsi: mpt3sas: Fix return value check of dma_get_required_mask() > > e7fafef9830c4a01e60f76e3860a9bef0262378d scsi: mpt3sas: Force PCIe scatterlist allocations to be within same 4 GB region > > ea10a652ad2ae2cf3eced6f632a5c98f26727057 scsi: mpt3sas: Fix use-after-free warning > > > > Sreekanth and Suganath, can you help with bisecting this issue? For the > > full report, see also https://lore.kernel.org/linux-scsi/Y1JkuKTjVYrOWbvm@xxxxxxxxxxx/. > > This issue is getting observed after having the below patch changes, > 2b9aba0c5d58e141e32bb1bb4c7cd91d19f075b8 scsi: mpt3sas: Fix return > value check of dma_get_required_mask() reverting this patch fixed the issue for us. > What is happening is that on Xen hypervisor, this > dma_get_required_mask() API always returns a 32 bit DMA mask. I.e. It > says that the minimum DMA mask required to access the host memory is > 32 bit and hence mpt3sas driver is setting the DMA mask to 32bit. So, > on a 64 bit machine, if the driver set's the DMA mask to 32 bit then > SWIOTLB's bounce buffer comes into picture during IOs. Since these > bounce buffers are limited in size and hence we observe the IO hang if > the large IOs are issued. I am not sure about what is going on here but while reverting the above patch, I added a printk right above the if: | printk("dma_get_required_mask =%lld\n",dma_get_required_mask(&pdev->dev)); which always (as in booting dom0 with 2GB, 4GB, 16GB and booting bare metal with 256GB) returns 4294967295 (DMA_BIT_MASK(32)). > I am not sure whether this API's return value is correct or not in the > Xen environment. If it is correct then I have to modify the driver to > not use this API and directly set the DMA mask to 64 bit if the system > is a 64bit machine. Obviously, our server always reports a 32bit mask which works just fine in the bare metal case but does not in the xen dom0 case. Is there anything I can do to help tracking the issue down? thanks and all the best, Adi > Thanks, > Sreekanth > > > > > > > Thanks, > > > > Bart.
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