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Subject: Re: [PATCH v1] virtio-mem: minor clarification regarding read-access to unplugged blocks
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>
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