On Mon, 16 Nov 2020 20:16:29 +0100
David Hildenbrand <> 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 <>
> Cc: Marek Kedzierski <>
> Cc: Michael S. Tsirkin <>
> Cc: Cornelia Huck <>
> Signed-off-by: David Hildenbrand <>
> ---
> virtio-mem.tex | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
Looks reasonable to me.
Acked-by: Cornelia Huck <>
