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

[Igor Mammedov]

On Tue, 24 Mar 2015 17:34:29 +0800
Zhu Guihua <address@hidden> wrote:

> 
> 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.
it shouldn't cause panic if it only clears flag in QEMU
(that's what it should do).


> 
> >>>>                        }
> >>>>                        // 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)?
I wouldn't check if device is present.
I'd unconditionally clear it and make sure on QEMU side that
operation is NOP if device is not present.

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