Re: [Qemu-devel] [RESEND PATCH v4 6/6] acpi: Add hardware implementation for memory hot unplug

[Zhu Guihua]

On 03/23/2015 08:47 PM, Igor Mammedov wrote:
> On Mon, 23 Mar 2015 18:59:28 +0800
> Zhu Guihua <address@hidden> wrote:
>
> > On 03/16/2015 10:59 PM, Igor Mammedov wrote:
> > [...]
> > >    
> > > diff --git a/hw/i386/acpi-dsdt-mem-hotplug.dsl b/hw/i386/acpi-dsdt-mem-hotplug.dsl
> > > index 1e9ec39..ef847e2 100644
> > > --- a/hw/i386/acpi-dsdt-mem-hotplug.dsl
> > > +++ b/hw/i386/acpi-dsdt-mem-hotplug.dsl
> > > @@ -29,6 +29,7 @@
> > >                External(MEMORY_SLOT_PROXIMITY, FieldUnitObj) // read only
> > >                External(MEMORY_SLOT_ENABLED, FieldUnitObj) // 1 if enabled, 
> > > read only
> > >                External(MEMORY_SLOT_INSERT_EVENT, FieldUnitObj) // (read) 1 if 
> > > has a insert event. (write) 1 to clear event
> > > +            External(MEMORY_SLOT_REMOVE_EVENT, FieldUnitObj) // (read) 1 if 
> > > has a remove event. (write) 1 to clear event
> > >                External(MEMORY_SLOT_SLECTOR, FieldUnitObj) // DIMM selector, 
> > > write only
> > >                External(MEMORY_SLOT_OST_EVENT, FieldUnitObj) // _OST event 
> > > code, write only
> > >                External(MEMORY_SLOT_OST_STATUS, FieldUnitObj) // _OST status 
> > > code, write only
> > > @@ -55,6 +56,8 @@
> > >                        If (LEqual(MEMORY_SLOT_INSERT_EVENT, One)) { // Memory 
> > > device needs check
> > >                            MEMORY_SLOT_NOTIFY_METHOD(Local0, 1)
> > >                            Store(1, MEMORY_SLOT_INSERT_EVENT)
> > > +                    } Elseif (LEqual(MEMORY_SLOT_REMOVE_EVENT, One)) { // 
> > > Ejection request
> > > +                        MEMORY_SLOT_NOTIFY_METHOD(Local0, 3)
> > > clear removing field here.
> > You mean clear remove event here?
> yes

I tested this method, clear remove event here will lead to guest
kernel panic.

> > > >                        }
> > > >                        // TODO: handle memory eject request
> > > >                        Add(Local0, One, Local0) // goto next DIMM
> > > > @@ -156,5 +159,12 @@
> > > >                    Store(Arg2, MEMORY_SLOT_OST_STATUS)
> > > >                    Release(MEMORY_SLOT_LOCK)
> > > >                }
> > > > +
> > > > +            Method(MEMORY_SLOT_EJECT_METHOD, 2) {
> > > > +                Acquire(MEMORY_SLOT_LOCK, 0xFFFF)
> > > > +                Store(ToInteger(Arg0), MEMORY_SLOT_SLECTOR) // select DIMM
> > > > +                Store(One, MEMORY_SLOT_REMOVE_EVENT)
> > > redo it using enabled field. Otherwise it could cause guest/QEMU crash:
> > >
> > > - if 1st memory was asked to be removed
> > > - then OSPM processes it but has not called _EJ0 yet leaving is_removed set
> > > - then QEMU adds/removes another DIMM triggering slots scan
> > >      which would issue second Notify(remove) since is_removed is still set
> > > - as result it will cause failure in OSPM or in QEMU if OSPM issues double EJ0()
> > If OSPM processed the ejection request but not called _EJ0, the device
> > will still be present in qemu,
> > we must handle this.
> There is nothing to handle in this case, if OSPM hasn't called _EJ0 then
> nothing happens and device stays in QEMU.
>
> > So I think OSPM issues double EJ0 maybe reasonable
> > in this situation.
> > What's your opinion?
> the first _EJ0 must do ejection, as for the second I think it should be NOP.

So we should judge the enabled field to check whether the device is 
present before
issuing Notify(remove)?

Thanks,
Zhu

> > Thanks,
> > Zhu
> [...]
> .