Re: [PATCH v1 3/9] Documentation: KVM: s390: Describe KVM_S390_MEMOP_F_CMPXCHG

[Thomas Huth]

On 04/10/2022 20.51, Janis Schoetterl-Glausch wrote:
> On Tue, 2022-10-04 at 10:16 +0200, Thomas Huth wrote:
> > On 30/09/2022 23.07, Janis Schoetterl-Glausch wrote:
> > > Describe the semantics of the new KVM_S390_MEMOP_F_CMPXCHG flag for
> > > absolute vm write memops which allows user space to perform (storage key
> > > checked) cmpxchg operations on guest memory.
> > >
> > > Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>
> > > ---
> > >    Documentation/virt/kvm/api.rst | 18 +++++++++++++++++-
> > >    1 file changed, 17 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> > > index abd7c32126ce..0e02d66e38ae 100644
> > > --- a/Documentation/virt/kvm/api.rst
> > > +++ b/Documentation/virt/kvm/api.rst
> > > @@ -3771,6 +3771,7 @@ Parameters are specified via the following structure::
> > >    		struct {
>
> What is the reason you initially didn't copy the /* in */ comment here?

You mean in commit 41408c28f283b ? Uh, don't ask me, that's more than 7 
years ago...

Anyway, please be aware that the MEMOP ioctl is defined as IOW only:

#define KVM_S390_MEM_OP _IOW(KVMIO, 0xb1, struct kvm_s390_mem_op)

... so if you now introduce an "out" field in that struct, this might have 
some impact, e.g. on Valgrind etc.

 Thomas