Re: [Qemu-devel] [PATCH v3 07/10] hw/arm/virt: Introduce opt-in feature "fdt"

[Shameerali Kolothum Thodi]

> -----Original Message-----
> From: Auger Eric [mailto:address@hidden
> Sent: 29 March 2019 09:32
> To: Shameerali Kolothum Thodi <address@hidden>;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden;
> address@hidden; address@hidden
> Cc: Linuxarm <address@hidden>; xuwei (O) <address@hidden>;
> Laszlo Ersek <address@hidden>; Ard Biesheuvel
> <address@hidden>; Leif Lindholm <address@hidden>
> Subject: Re: [PATCH v3 07/10] hw/arm/virt: Introduce opt-in feature "fdt"
> 
> Hi Shameer,
> 
> [ + Laszlo, Ard, Leif ]
> 
> On 3/21/19 11:47 AM, Shameer Kolothum wrote:
> > This is to disable/enable populating DT nodes in case
> > any conflict with acpi tables. The default is "off".
> The name of the option sounds misleading to me. Also we don't really
> know the scope of the disablement. At the moment this just aims to
> prevent the hotpluggable dt nodes from being added if we boot in ACPI mode.
> 
> >
> > This will be used in subsequent patch where cold plug
> > device-memory support is added for DT boot.
> I am concerned about the fact that in dt mode, by default, you won't see
> any PCDIMM nodes.
> >
> > If DT memory node support is added for cold-plugged device
> > memory, those memory will be visible to Guest kernel via
> > UEFI GetMemoryMap() and gets treated as early boot memory.
> Don't we have an issue in UEFI then. Normally the SRAT indicates whether
> the slots are hotpluggable or not. Shouldn't the UEFI code look at this
> info.

Sorry I missed this part. Yes, that will be a more cleaner solution.

Also, to be more clear on what happens,

Guest ACPI boot with "fdt=on" ,

From kernel log,

[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000040000000-0x00000000bbf5ffff]
[    0.000000]   node   0: [mem 0x00000000bbf60000-0x00000000bbffffff]
[    0.000000]   node   0: [mem 0x00000000bc000000-0x00000000bc02ffff]
[    0.000000]   node   0: [mem 0x00000000bc030000-0x00000000bc36ffff]
[    0.000000]   node   0: [mem 0x00000000bc370000-0x00000000bf64ffff]
[    0.000000]   node   0: [mem 0x00000000bf650000-0x00000000bf6dffff]
[    0.000000]   node   0: [mem 0x00000000bf6e0000-0x00000000bf6effff]
[    0.000000]   node   0: [mem 0x00000000bf6f0000-0x00000000bf80ffff]
[    0.000000]   node   0: [mem 0x00000000bf810000-0x00000000bfffffff]
[    0.000000]   node   0: [mem 0x00000000c0000000-0x00000000ffffffff]  --> 
This is the hotpluggable memory node from DT.
[    0.000000] Zeroed struct page in unavailable ranges: 1040 pages
[    0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x00000000ffffffff]


Guest ACPI boot with "fdt=off" ,

[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000040000000-0x00000000bbf5ffff]
[    0.000000]   node   0: [mem 0x00000000bbf60000-0x00000000bbffffff]
[    0.000000]   node   0: [mem 0x00000000bc000000-0x00000000bc02ffff]
[    0.000000]   node   0: [mem 0x00000000bc030000-0x00000000bc36ffff]
[    0.000000]   node   0: [mem 0x00000000bc370000-0x00000000bf64ffff]
[    0.000000]   node   0: [mem 0x00000000bf650000-0x00000000bf6dffff]
[    0.000000]   node   0: [mem 0x00000000bf6e0000-0x00000000bf6effff]
[    0.000000]   node   0: [mem 0x00000000bf6f0000-0x00000000bf80ffff]
[    0.000000]   node   0: [mem 0x00000000bf810000-0x00000000bfffffff]
[    0.000000] Zeroed struct page in unavailable ranges: 1040 pages
[    0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x00000000bfffffff

The hotpluggable memory node is absent from early memory nodes here.

As you said, it could be possible to detect this node using SRAT in UEFI.

Cheers,
Shameer

> > Hence memory becomes non hot-un-unpluggable even if Guest
> > is booted in ACPI mode.
> 
> 
> 
> >
> > Signed-off-by: Shameer Kolothum <address@hidden>
> > ---
> >  hw/arm/virt.c         | 23 +++++++++++++++++++++++
> >  include/hw/arm/virt.h |  1 +
> >  2 files changed, 24 insertions(+)
> >
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index 13db0e9..b602151 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -1717,6 +1717,20 @@ static void virt_set_highmem(Object *obj, bool
> value, Error **errp)
> >      vms->highmem = value;
> >  }
> >
> > +static bool virt_get_fdt(Object *obj, Error **errp)
> > +{
> > +    VirtMachineState *vms = VIRT_MACHINE(obj);
> > +
> > +    return vms->use_fdt;
> > +}
> > +
> > +static void virt_set_fdt(Object *obj, bool value, Error **errp)
> > +{
> > +    VirtMachineState *vms = VIRT_MACHINE(obj);
> > +
> > +    vms->use_fdt = value;
> > +}
> > +
> >  static bool virt_get_its(Object *obj, Error **errp)
> >  {
> >      VirtMachineState *vms = VIRT_MACHINE(obj);
> > @@ -2005,6 +2019,15 @@ static void virt_instance_init(Object *obj)
> >      object_property_set_description(obj, "gic-version",
> >                                      "Set GIC version. "
> >                                      "Valid values are 2, 3 and host",
> NULL);
> > +    /* fdt is disabled by default */
> > +    vms->use_fdt = false;
> > +    object_property_add_bool(obj, "fdt", virt_get_fdt,
> > +                             virt_set_fdt, NULL);
> > +    object_property_set_description(obj, "fdt",
> > +                                    "Set on/off to enable/disable
> device tree "
> > +                                    "nodes in case any conflict with
> ACPI"
> in case of
> 
> Thanks
> 
> Eric
> > +                                    "(eg: device memory node)",
> > +                                    NULL);
> >
> >      vms->highmem_ecam = !vmc->no_highmem_ecam;
> >
> > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> > index c5e4c96..14b2e0a 100644
> > --- a/include/hw/arm/virt.h
> > +++ b/include/hw/arm/virt.h
> > @@ -119,6 +119,7 @@ typedef struct {
> >      bool highmem_ecam;
> >      bool its;
> >      bool virt;
> > +    bool use_fdt;
> >      int32_t gic_version;
> >      VirtIOMMUType iommu;
> >      struct arm_boot_info bootinfo;
> >