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

[David Hildenbrand <david@redhat.com>]

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