From: Jason Wang <jasowang@redhat.com> To: Peter Xu <peterx@redhat.com> Cc: xuanzhuo@linux.alibaba.com, mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xieyongji@bytedance.com, Maxime Coquelin <maxime.coquelin@redhat.com>, eperezma@redhat.com, david.marchand@redhat.com Subject: Re: [RFC 0/2] vduse: add support for networking devices Date: Fri, 21 Apr 2023 15:08:59 +0800 [thread overview] Message-ID: <CACGkMEvtBQg5fTTzSaMRwZH7P3WiDx0=eov9RdCtSFaHVtbh1w@mail.gmail.com> (raw) In-Reply-To: <ZEGG2GJw2DQk689j@x1n> On Fri, Apr 21, 2023 at 2:39 AM Peter Xu <peterx@redhat.com> wrote: > > 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: Interesting, but there're indeed cases where VM_DONTEXPAND is used by non-driver codes. The pages mapped by VDUSE are not device driver pages but the IOTLB and virtqueue. Btw the definition of VM_SPECIAL doesn't say anything related to dump: /* * Special vmas that are non-mergable, non-mlock()able. */ #define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP) > > 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@linux.ibm.com/ This seems similar to the case of VDUSE. Thanks > > Thanks, > > -- > Peter Xu > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
WARNING: multiple messages have this Message-ID (diff)
From: Jason Wang <jasowang@redhat.com> To: Peter Xu <peterx@redhat.com> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>, xieyongji@bytedance.com, mst@redhat.com, david.marchand@redhat.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, xuanzhuo@linux.alibaba.com, eperezma@redhat.com Subject: Re: [RFC 0/2] vduse: add support for networking devices Date: Fri, 21 Apr 2023 15:08:59 +0800 [thread overview] Message-ID: <CACGkMEvtBQg5fTTzSaMRwZH7P3WiDx0=eov9RdCtSFaHVtbh1w@mail.gmail.com> (raw) In-Reply-To: <ZEGG2GJw2DQk689j@x1n> On Fri, Apr 21, 2023 at 2:39 AM Peter Xu <peterx@redhat.com> wrote: > > 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: Interesting, but there're indeed cases where VM_DONTEXPAND is used by non-driver codes. The pages mapped by VDUSE are not device driver pages but the IOTLB and virtqueue. Btw the definition of VM_SPECIAL doesn't say anything related to dump: /* * Special vmas that are non-mergable, non-mlock()able. */ #define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP) > > 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@linux.ibm.com/ This seems similar to the case of VDUSE. Thanks > > Thanks, > > -- > Peter Xu >
next prev parent reply other threads:[~2023-04-21 7:09 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-04-19 13:43 [RFC 0/2] vduse: add support for networking devices Maxime Coquelin 2023-04-19 13:43 ` Maxime Coquelin 2023-04-19 13:43 ` [RFC 1/2] vduse: validate block features only with block devices Maxime Coquelin 2023-04-19 13:43 ` Maxime Coquelin 2023-04-20 4:06 ` Jason Wang 2023-04-20 4:06 ` Jason Wang 2023-04-20 10:22 ` Maxime Coquelin 2023-04-20 10:22 ` Maxime Coquelin 2023-04-19 13:43 ` [RFC 2/2] vduse: enable Virtio-net device type Maxime Coquelin 2023-04-19 13:43 ` Maxime Coquelin 2023-04-20 4:34 ` [RFC 0/2] vduse: add support for networking devices Jason Wang 2023-04-20 4:34 ` Jason Wang 2023-04-20 14:16 ` Maxime Coquelin 2023-04-20 14:16 ` Maxime Coquelin 2023-04-21 5:51 ` Jason Wang 2023-04-21 5:51 ` Jason Wang 2023-04-21 14:28 ` Maxime Coquelin 2023-04-21 14:28 ` Maxime Coquelin 2023-04-23 6:30 ` Jason Wang 2023-04-23 6:30 ` Jason Wang 2023-04-23 8:22 ` Yongji Xie 2023-04-24 3:42 ` Jason Wang 2023-04-24 3:42 ` Jason Wang 2023-04-20 18:39 ` Peter Xu 2023-04-20 18:39 ` Peter Xu 2023-04-21 7:08 ` Jason Wang [this message] 2023-04-21 7:08 ` Jason Wang 2023-04-20 8:13 ` Yongji Xie 2023-04-20 14:23 ` Maxime Coquelin 2023-04-20 14:23 ` Maxime Coquelin
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