Re: [PATCH v3 0/6] use IOVAs check based on DMA mask

[Thomas Monjalon <thomas@monjalon.net>]

29/10/2018 09:23, Yao, Lei A:
> Hi, Lucero, Thomas
> 
> This patch set will cause deadlock during memory initialization. 
> rte_memseg_walk and try_expand_heap both will lock 
> the file &mcfg->memory_hotplug_lock. So dead lock will occur. 
> 
> #0       rte_memseg_walk
> #1  <-rte_eal_check_dma_mask
> #2  <-alloc_pages_on_heap
> #3  <-try_expand_heap_primary   
> #4  <-try_expand_heap
> 
> Log as following:
> EAL: TSC frequency is ~2494156 KHz
> EAL: Master lcore 0 is ready (tid=7ffff7fe3c00;cpuset=[0])
> [New Thread 0x7ffff5e0d700 (LWP 330350)]
> EAL: lcore 1 is ready (tid=7ffff5e0d700;cpuset=[1])
> EAL: Trying to obtain current memory policy.
> EAL: Setting policy MPOL_PREFERRED for socket 0
> EAL: Restoring previous memory policy: 0
> 
> Could you have a check on this? A lot of test cases in our validation 
> team fail because of this. Thanks a lot!

Can we just call rte_memseg_walk_thread_unsafe()?

+Cc Anatoly


> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> > 05/10/2018 14:45, Alejandro Lucero:
> > > I sent a patchset about this to be applied on 17.11 stable. The memory
> > > code has had main changes since that version, so here it is the patchset
> > > adjusted to current master repo.
> > >
> > > This patchset adds, mainly, a check for ensuring IOVAs are within a
> > > restricted range due to addressing limitations with some devices. There
> > > are two known cases: NFP and IOMMU VT-d emulation.
> > >
> > > With this check IOVAs out of range are detected and PMDs can abort
> > > initialization. For the VT-d case, IOVA VA mode is allowed as long as
> > > IOVAs are within the supported range, avoiding to forbid IOVA VA by
> > > default.
> > >
> > > For the addressing limitations known cases, there are just 40(NFP) or
> > > 39(VT-d) bits for handling IOVAs. When using IOVA PA, those limitations
> > > imply 1TB(NFP) or 512M(VT-d) as upper limits, which is likely enough for
> > > most systems. With machines using more memory, the added check will
> > > ensure IOVAs within the range.
> > >
> > > With IOVA VA, and because the way the Linux kernel serves mmap calls
> > > in 64 bits systems, 39 or 40 bits are not enough. It is possible to
> > > give an address hint with a lower starting address than the default one
> > > used by the kernel, and then ensuring the mmap uses that hint or hint plus
> > > some offset. With 64 bits systems, the process virtual address space is
> > > large enoguh for doing the hugepages mmaping within the supported
> > range
> > > when those addressing limitations exist. This patchset also adds a change
> > > for using such a hint making the use of IOVA VA a more than likely
> > > possibility when there are those addressing limitations.
> > >
> > > The check is not done by default but just when it is required. This
> > > patchset adds the check for NFP initialization and for setting the IOVA
> > > mode is an emulated VT-d is detected. Also, because the recent patchset
> > > adding dynamic memory allocation, the check is also invoked for ensuring
> > > the new memsegs are within the required range.
> > >
> > > This patchset could be applied to stable 18.05.
> > 
> > Applied, thanks