On 16.11.23 03:45, Xiaoyao Li wrote:
On 11/16/2023 1:54 AM, David Hildenbrand wrote:
On 15.11.23 08:14, Xiaoyao Li wrote:
Add KVM guest_memfd support to RAMBlock so both normal hva based memory
and kvm guest memfd based private memory can be associated in one
RAMBlock.
Introduce new flag RAM_GUEST_MEMFD. When it's set, it calls KVM ioctl to
create private guest_memfd during RAMBlock setup.
Note, RAM_GUEST_MEMFD is supposed to be set for memory backends of
confidential guests, such as TDX VM. How and when to set it for memory
backends will be implemented in the following patches.
Can you elaborate (and add to the patch description if there is good
reason) why we need that flag and why we cannot simply rely on the VM
type instead to decide whether to allocate a guest_memfd or not?
The reason is, relying on the VM type is sort of hack that we need to
get the MachineState instance and retrieve the vm type info. I think
it's better not to couple them.
More importantly, it's not flexible and extensible for future case that
not all the memory need guest memfd.
Okay. In that case, please update the documentation of all functions
where we are allowed to pass in RAM_GUEST_MEMFD. There are a couple of
them in include/exec/memory.h
I'll note that the name/terminology of "RAM_GUEST_MEMFD" is extremely
Linux+kvm specific. But I cannot really come up with something better
right now.
--
Cheers,
David / dhildenb
