Re: [PATCH for-5.0] xen: fixup RAM memory region initialization

[Igor Mammedov <imammedo@redhat.com>]

Paolo,

could you take it along with Olaf's xenfv patch?


On Fri, 27 Mar 2020 06:48:28 -0400
Igor Mammedov <imammedo@redhat.com> wrote:

> Since bd457782b3b0 ("x86/pc: use memdev for RAM") Xen
> machine fails to start with:
>    qemu-system-i386: xen: failed to populate ram at 0
> 
> The reason is that xen_ram_alloc() which is called by
> memory_region_init_ram(), compares memory region with
> statically allocated 'global' ram_memory memory region
> that it uses for RAM, and does nothing in case it matches.
> 
> While it's possible feed machine->ram to xen_ram_alloc()
> in the same manner to keep that hack working, I'd prefer
> not to keep that circular dependency and try to untangle that.
> 
> However it doesn't look trivial to fix, so as temporary
> fixup opt out Xen machine from memdev based RAM allocation,
> and let xen_ram_alloc() do its trick for now.
> 
> Reported-by: Anthony PERARD <anthony.perard@citrix.com>
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
> PS:
>    - compile tested only
> 
>  hw/i386/pc_piix.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index e6756216f9..6cb352363d 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -953,6 +953,10 @@ static void xenfv_machine_options(MachineClass *m)
>      m->desc = "Xen Fully-virtualized PC";
>      m->max_cpus = HVM_MAX_VCPUS;
>      m->default_machine_opts = "accel=xen";
> +    /*
> +     * opt out of system RAM being allocated by generic code
> +     */
> +    m->default_ram_id = NULL;
>  }
>  
>  DEFINE_PC_MACHINE(xenfv, "xenfv", pc_xen_hvm_init,