Re: [RFC 0/2] Introduce MMIO/PIO dispatch file descriptors (ioregionfd)

[Stefan Hajnoczi <stefanha@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 1723 bytes --]

On Tue, Dec 29, 2020 at 01:02:42PM +0300, Elena Afanasova wrote:
> This patchset introduces a KVM dispatch mechanism which can be used 
> for handling MMIO/PIO accesses over file descriptors without returning 
> from ioctl(KVM_RUN). This allows device emulation to run in another task 
> separate from the vCPU task.
> 
> This is achieved through KVM vm ioctl for registering MMIO/PIO regions and 
> a wire protocol that KVM uses to communicate with a task handling an 
> MMIO/PIO access.
> 
> ioregionfd relies on kmemcg in order to limit the amount of kernel memory 
> that userspace can consume. Can NR_IOBUS_DEVS hardcoded limit be enforced 
> only in case kmemcg is disabled?

Thanks for sharing this! Can you describe the todos? I noticed some in
Patch 1 and highlighted them. In addition:
 * Signal handling when the vCPU thread is interrupted in
   kernel_read()/kernel_write()

> Elena Afanasova (2):
>   KVM: add initial support for KVM_SET_IOREGION
>   KVM: add initial support for ioregionfd blocking read/write operations
> 
>  arch/x86/kvm/Kconfig     |   1 +
>  arch/x86/kvm/Makefile    |   1 +
>  arch/x86/kvm/x86.c       |   1 +
>  include/linux/kvm_host.h |  17 ++
>  include/uapi/linux/kvm.h |  23 +++
>  virt/kvm/Kconfig         |   3 +
>  virt/kvm/eventfd.c       |  25 +++
>  virt/kvm/eventfd.h       |  14 ++
>  virt/kvm/ioregion.c      | 390 +++++++++++++++++++++++++++++++++++++++
>  virt/kvm/ioregion.h      |  15 ++
>  virt/kvm/kvm_main.c      |  20 +-
>  11 files changed, 507 insertions(+), 3 deletions(-)
>  create mode 100644 virt/kvm/eventfd.h
>  create mode 100644 virt/kvm/ioregion.c
>  create mode 100644 virt/kvm/ioregion.h
> 
> -- 
> 2.25.1
> 

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]