On Thu, Apr 20, 2023 at 12:34:06PM +0800, Jason Wang wrote: > > 3. Coredump: > > In order to be able to perform post-mortem analysis, DPDK > > Vhost library marks pages used for vrings and descriptors > > buffers as MADV_DODUMP using madvise(). However with > > VDUSE it fails with -EINVAL. My understanding is that we > > set VM_DONTEXPAND flag to the VMAs and madvise's > > MADV_DODUMP fails if it is present. I'm not sure to > > understand why madvise would prevent MADV_DODUMP if > > VM_DONTEXPAND is set. Any thoughts? > > Adding Peter who may know the answer. I don't.. but I had a quick look, it seems that VM_DONTEXPAND was kind of reused (and I'm not sure whether it's an abuse or not so far..) to represent device driver pages since removal of VM_RESERVED: https://lore.kernel.org/all/20120731103457.20182.88454.stgit@zurg/ https://lore.kernel.org/all/20120731103503.20182.94365.stgit@zurg/ But I think that change at least breaks hugetlb once so there's the explicit hugetlb check to recover that behavior back: https://lore.kernel.org/all/20180930054629.29150-1-daniel@xxxxxxxxxxxxx/ Thanks, -- Peter Xu _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
