Re: [Qemu-devel] [PATCH v2 0/2] kvm: use kvm_vm_check_extension() with VM capabilities

[Greg Kurz]

Ping ?

On Thu, 21 Sep 2017 18:00:41 +0200
Greg Kurz <address@hidden> wrote:

> Some VM capabilities are currently checked with kvm_check_extension(). This
> doesn't have any impact for most host architectures because they don't depend
> on the KVM type. However, this is a problem for server-class ppc hosts that
> can support the PR and HV KVM types. Both implementations can co-exist in the
> kernel at the same time and we decide which one will be used with the "type"
> argument of the KVM_CREATE_VM ioctl.
> 
> Each KVM type has a different set of capabilities, and checking them with
> kvm_check_extension() will always cause KVM to assume we're in HV mode,
> even if they are VM specific and we have explicitely requested to run in
> PR mode. This may produce unexpected results.
> 
> Similar issues were recently fixed in the ppc code:
> 
> https://github.com/qemu/qemu/commit/70a0c19e83aa4c71c879d51e426e89e4b3d4e014
> https://github.com/dgibson/qemu/commit/b152d74ebaed61f89fa1ab2c9b1526d9e9dabae5
> 
> This series focuses on capabilities that are checked by the common code.
> 
> --
> Greg
> 
> ---
> 
> Greg Kurz (2):
>       kvm: check KVM_CAP_SYNC_MMU with kvm_vm_check_extension()
>       kvm: check KVM_CAP_NR_VCPUS with kvm_vm_check_extension()
> 
> 
>  accel/kvm/kvm-all.c    |   51 
> +++++++++++++++++++++++++-----------------------
>  accel/stubs/kvm-stub.c |    4 ++--
>  include/sysemu/kvm.h   |    2 +-
>  3 files changed, 30 insertions(+), 27 deletions(-)
> 
>