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From: Peter Xu <peterx@redhat.com>
To: Jason Wang <jasowang@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: Thu, 20 Apr 2023 14:39:20 -0400	[thread overview]
Message-ID: <ZEGG2GJw2DQk689j@x1n> (raw)
In-Reply-To: <CACGkMEuiHqPkqYk1ZG3RZXLjm+EM3bmR0v1T1yH-ADEazOwTMA@mail.gmail.com>

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@linux.ibm.com/

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: Peter Xu <peterx@redhat.com>
To: Jason Wang <jasowang@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: Thu, 20 Apr 2023 14:39:20 -0400	[thread overview]
Message-ID: <ZEGG2GJw2DQk689j@x1n> (raw)
In-Reply-To: <CACGkMEuiHqPkqYk1ZG3RZXLjm+EM3bmR0v1T1yH-ADEazOwTMA@mail.gmail.com>

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@linux.ibm.com/

Thanks,

-- 
Peter Xu


  parent reply	other threads:[~2023-04-20 18:39 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 [this message]
2023-04-20 18:39     ` Peter Xu
2023-04-21  7:08     ` Jason Wang
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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