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Subject: Re: [virtio-comment] Re: [PATCH v1] virtio-mem: minor clarification regarding read-access to unplugged blocks
On 27.11.20 12:02, Cornelia Huck wrote: > On Fri, 27 Nov 2020 11:39:50 +0100 > David Hildenbrand <david@redhat.com> wrote: > >> On 20.11.20 16:13, Cornelia Huck wrote: >>> On Mon, 16 Nov 2020 20:16:29 +0100 >>> David Hildenbrand <david@redhat.com> wrote: >>> >>>> Let's clarify that we don't expect all DMA to work with unplugged blocks. >>>> We really only give guarantees when reading from unplugged memory blocks >>>> via the CPU, e.g., as done by Linux when creating a system dump via >>>> kdump: the new kernel will copy the content of the old (crashed) kernel >>>> via the CPU to user space, from where it will find its final destination >>>> inside the dump file. Note that dumping via makedumpfile under Linux will >>>> avoid reading unplugged blocks completely. >>>> >>>> This is a preparation for device passthrough to VMs, whereby such >>>> dedicated devices might not be able to read from unplugged memory blocks. >>>> >>>> Let's document that this scenario is possible, and why this handling is >>>> in place at all. >>>> >>>> Cc: teawater <teawaterz@linux.alibaba.com> >>>> Cc: Marek Kedzierski <mkedzier@redhat.com> >>>> Cc: Michael S. Tsirkin <mst@redhat.com> >>>> Cc: Cornelia Huck <cohuck@redhat.com> >>>> Signed-off-by: David Hildenbrand <david@redhat.com> >>>> --- >>>> virtio-mem.tex | 9 +++++++-- >>>> 1 file changed, 7 insertions(+), 2 deletions(-) >>> >>> Looks reasonable to me. >>> >>> Acked-by: Cornelia Huck <cohuck@redhat.com> >> >> Thanks! >> >> I assume I'll need a github issue etc. to get this in, right? >> > > Yes; just open the issue, point to this patch in the archives, and > reply with the issue here. > > (I don't think this is trivial enough to push without voting.) > Makes sense. I'll wait a bit more. Thanks! -- Thanks, David / dhildenb
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