Re: [PATCH v1 7/9] memory: introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()

[David Hildenbrand]

On 03.03.21 12:35, Cornelia Huck wrote:
> On Tue, 2 Mar 2021 20:02:34 +0100
> David Hildenbrand <david@redhat.com> wrote:
>
> > On 02.03.21 18:32, Peter Xu wrote:
> > > On Tue, Feb 09, 2021 at 02:49:37PM +0100, David Hildenbrand wrote:
> > > > @@ -899,13 +899,17 @@ int kvm_s390_mem_op_pv(S390CPU *cpu, uint64_t offset, 
> > > > void *hostbuf,
> > > >     * to grow. We also have to use MAP parameters that avoid
> > > >     * read-only mapping of guest pages.
> > > >     */
> > > > -static void *legacy_s390_alloc(size_t size, uint64_t *align, bool shared)
> > > > +static void *legacy_s390_alloc(size_t size, uint64_t *align, bool shared,
> > > > +                               bool noreserve)
> > > >    {
> > > >        static void *mem;
> > > >    
> > > >        if (mem) {
> > > >            /* we only support one allocation, which is enough for initial ram */
> > > >            return NULL;
> > > > +    } else if (noreserve) {
> > > > +        error_report("Skipping reservation of swap space is not supported.");
> > > > +        return NULL
> > >
> > > Semicolon missing.
> >
> > Thanks for catching that!
>
> Regardless of that (and this patch set), can we finally get rid of
> legacy_s390_alloc? We already fence off running with a kernel prior to
> 3.15, and KVM_CAP_S390_COW depends on ESOP -- are non-ESOP kvm hosts
> still relevant? This seems to be a generation 10 feature; do we
> realistically expect anyone running this on e.g. a z/VM host that
> doesn't provide ESOP?

Good question - last time I asked that question (~2 years ago) I was 
told that such z/VM environemnts are still relevant.

--
Thanks,

David / dhildenb