On Tue, 24 Mar 2015 18:48:02 +0800
Zhu Guihua <zhugh.f...@cn.fujitsu.com> wrote:
>
> On 03/24/2015 06:31 PM, Igor Mammedov wrote:
> > On Tue, 24 Mar 2015 17:38:53 +0800
> > Zhu Guihua <zhugh.f...@cn.fujitsu.com> wrote:
> >
> >> On 03/16/2015 10:59 PM, Igor Mammedov wrote:
> >>> On Mon, 16 Mar 2015 16:58:18 +0800
> >>> Zhu Guihua <zhugh.f...@cn.fujitsu.com> wrote:
> >>>
> >>>> This patch adds a new bit to memory hotplug IO port indicating that
> >>> actually bit was added in 2/6 where is_removing had been added.
> >>>
> >>>> EJ0 has been evaluated by guest OS. And call pc-dimm unplug cb to do
> >>>> the real removal.
> >>>>
> >>>> Signed-off-by: Zhu Guihua <zhugh.f...@cn.fujitsu.com>
> >>>> ---
> >>>> docs/specs/acpi_mem_hotplug.txt | 11 +++++++++--
> >>>> hw/acpi/memory_hotplug.c | 21 +++++++++++++++++++--
> >>>> hw/core/qdev.c | 2 +-
> >>>> hw/i386/acpi-build.c | 9 +++++++++
> >>>> hw/i386/acpi-dsdt-mem-hotplug.dsl | 10 ++++++++++
> >>>> include/hw/acpi/pc-hotplug.h | 2 ++
> >>>> include/hw/qdev-core.h | 1 +
> >>>> trace-events | 1 +
> >>>> 8 files changed, 52 insertions(+), 5 deletions(-)
> >>>>
> >>>> diff --git a/docs/specs/acpi_mem_hotplug.txt
> >>>> b/docs/specs/acpi_mem_hotplug.txt
> >>>> index 1290994..85cd4b8 100644
> >>>> --- a/docs/specs/acpi_mem_hotplug.txt
> >>>> +++ b/docs/specs/acpi_mem_hotplug.txt
> >>>> @@ -19,7 +19,9 @@ Memory hot-plug interface (IO port 0xa00-0xa17, 1-4
> >>>> byte access):
> >>>> 1: Device insert event, used to distinguish device for
> >>>> which
> >>>> no device check event to OSPM was issued.
> >>>> It's valid only when bit 1 is set.
> >>>> - 2-7: reserved and should be ignored by OSPM
> >>>> + 2: Device remove event, used to distinguish device for
> >>>> which
> >>>> + no device check event to OSPM was issued.
> >>>> + 3-7: reserved and should be ignored by OSPM
> >>>> [0x15-0x17] reserved
> >>>>
> >>>> write access:
> >>>> @@ -35,7 +37,12 @@ Memory hot-plug interface (IO port 0xa00-0xa17, 1-4
> >>>> byte access):
> >>>> 1: if set to 1 clears device insert event, set by OSPM
> >>>> after it has emitted device check event for the
> >>>> selected memory device
> >>>> - 2-7: reserved, OSPM must clear them before writing to
> >>>> register
> >>>> + 2: if set to 1 clears device remove event, set by OSPM
> >>>> + after it has emitted device check event for the
> >>>> + selected memory device. if guest fails to eject
> >>>> device, it
> >>>> + should send OST event about it and forget about device
> >>>> + removal.
> >>>> + 3-7: reserved, OSPM must clear them before writing to
> >>>> register
> >>>>
> >>>> Selecting memory device slot beyond present range has no effect on
> >>>> platform:
> >>>> - write accesses to memory hot-plug registers not documented above
> >>>> are
> >>>> diff --git a/hw/acpi/memory_hotplug.c b/hw/acpi/memory_hotplug.c
> >>>> index 687b2f1..d6b8c89 100644
> >>>> --- a/hw/acpi/memory_hotplug.c
> >>>> +++ b/hw/acpi/memory_hotplug.c
> >>>> @@ -2,6 +2,7 @@
> >>>> #include "hw/acpi/pc-hotplug.h"
> >>>> #include "hw/mem/pc-dimm.h"
> >>>> #include "hw/boards.h"
> >>>> +#include "hw/qdev-core.h"
> >>>> #include "trace.h"
> >>>> #include "qapi-event.h"
> >>>>
> >>>> @@ -91,6 +92,8 @@ static void acpi_memory_hotplug_write(void *opaque,
> >>>> hwaddr addr, uint64_t data,
> >>>> MemHotplugState *mem_st = opaque;
> >>>> MemStatus *mdev;
> >>>> ACPIOSTInfo *info;
> >>>> + DeviceState *dev = NULL;
> >>>> + HotplugHandler *hotplug_ctrl = NULL;
> >>>>
> >>>> if (!mem_st->dev_count) {
> >>>> return;
> >>>> @@ -122,19 +125,33 @@ static void acpi_memory_hotplug_write(void
> >>>> *opaque, hwaddr addr, uint64_t data,
> >>>> mdev = &mem_st->devs[mem_st->selector];
> >>>> mdev->ost_status = data;
> >>>> trace_mhp_acpi_write_ost_status(mem_st->selector,
> >>>> mdev->ost_status);
> >>>> - /* TODO: implement memory removal on guest signal */
> >>>>
> >>>> info = acpi_memory_device_status(mem_st->selector, mdev);
> >>>> qapi_event_send_acpi_device_ost(info, &error_abort);
> >>>> qapi_free_ACPIOSTInfo(info);
> >>>> break;
> >>>> - case 0x14:
> >>>> + case 0x14: /* set is_* fields */
> >>>> mdev = &mem_st->devs[mem_st->selector];
> >>>> if (data & 2) { /* clear insert event */
> >>>> mdev->is_inserting = false;
> >>>> trace_mhp_acpi_clear_insert_evt(mem_st->selector);
> >>>> + } else if (data & 4) { /* request removal of device */
> >>> fix comment to match docs above.
> >>>
> >>>> + mdev->is_removing = false;
> >>>> + trace_mhp_acpi_clear_remove_evt(mem_st->selector);
> >>> just clear event here and don't do removal part as it doesn't match
> >>> documentation you've written above regarding this field.
> >>>
> >>> It would be better to move is_removing handling from here to 2/6
> >>> + related ASL code from DSDT which should clear it after sending device
> >>> check.
> >>>
> >>>> + /*
> >>>> + * QEMU memory hot unplug is an asynchronous procedure.
> >>>> QEMU first
> >>>> + * calls pc-dimm unplug request cb to send a SCI to guest.
> >>>> When the
> >>>> + * guest OS finished handling the SCI, it evaluates ACPI
> >>>> EJ0, and
> >>>> + * QEMU calls pc-dimm unplug cb to remove memory device.
> >>>> + */
> >>> something like this comment, should be in acpi_mem_hotplug.txt not here.
> >>>
> >>>
> >>> There is 'is_enabled' field, which is 1 if device is present, we can use
> >>> it
> >>> for triggering actual ejecting in QEMU from EJ0(), something like:
> >>>
> >>> } else if (data & 1) { /* eject device */
> >> I think this is not correct. When you clear insert event, the
> >> 'is_enabled' filed was also 1.
> >> And when we hot remove memory, the addr 0x14 will be written only once.
> > It's not clear to me what a problem you see here.
> > Could you give more extended explanation, pls?
>
> When we clear insert event, 'data & 1' was also true, so unplug
> operation maybe called.
> This is only asumed situation, because when the addr is 0x14,
> acpi_memory_hotplug_write()
> will be called only once, and the value of data is 5, we could not
> execute the condition of 'data & 1',
> the unplug operation could not be called.
Looks like there is a bug that wouldn't allow us to reuse
MEMORY_SLOT_ENABLED bit for removal, acpi_mem_hotplug.txt clearly states
that 0 bit must be cleared and marks it as reserved.
It's caused by
Field(MEMORY_HOTPLUG_IO_REGION, ByteAcc, NoLock, Preserve) {
^^^^^^^^
Offset(20),
MEMORY_SLOT_ENABLED, 1, // 1 if enabled, read only
MEMORY_SLOT_INSERT_EVENT, 1, // (read) 1 if has a insert event.
(write) 1 to clear event
}
the fact that flags field is declared with "Preserve" update rule[1].
We can't fix it since that old guest (with Preserve UpdateRule) migrated
to new QEMU will always write to 1st bit whatever value it has had
the rest of reserved bits would be always 0 since old guest doesn't use
them on read side.
However since read/write semantics of fields are different, I'd fix
UpdateRule to WriteAsZeros and update protocol documentation as follow:
diff --git a/docs/specs/acpi_mem_hotplug.txt b/docs/specs/acpi_mem_hotplug.txt
index 1290994..e2cfbfc 100644
--- a/docs/specs/acpi_mem_hotplug.txt
+++ b/docs/specs/acpi_mem_hotplug.txt
@@ -19,7 +19,9 @@ Memory hot-plug interface (IO port 0xa00-0xa17, 1-4 byte
access):
1: Device insert event, used to distinguish device for which
no device check event to OSPM was issued.
It's valid only when bit 1 is set.
- 2-7: reserved and should be ignored by OSPM
+ 2: Device remove event, used to distinguish device for which
+ no device check event to OSPM was issued.
+ 3-7: reserved and should be ignored by OSPM
[0x15-0x17] reserved
write access:
@@ -31,11 +33,19 @@ Memory hot-plug interface (IO port 0xa00-0xa17, 1-4 byte
access):
[0xc-0x13] reserved, writes into it are ignored
[0x14] Memory device control fields
bits:
- 0: reserved, OSPM must clear it before writing to register
+ 0: reserved, OSPM must clear it before writing to register.
+ Due to BUG in versions prior 2.4 that field isn't
+ cleared when other fields are written.Keep it reserved
+ and don't try to reuse it.
1: if set to 1 clears device insert event, set by OSPM
after it has emitted device check event for the
selected memory device
- 2-7: reserved, OSPM must clear them before writing to register
+ 2: if set to 1 clears device remove event, set by OSPM
+ after it has emitted device check event for the
+ selected memory device
+ 3: if set to 1 initiates device eject, set by OSPM when it
+ triggers memory device removal and calls _EJ0 method
+ 4-7: reserved, OSPM must clear them before writing to register
and extend aml_field() to support UpdateRule + modify acpi-build.c as follow:
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index d0a5c85..4e81dda 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -922,7 +922,8 @@ build_ssdt(GArray *table_data, GArray *linker,
aml_named_field(stringify(MEMORY_SLOT_PROXIMITY), 32));
aml_append(scope, field);
- field = aml_field(stringify(MEMORY_HOTPLUG_IO_REGION), aml_byte_acc);
+ field = aml_field(stringify(MEMORY_HOTPLUG_IO_REGION), aml_byte_acc,
+ aml_write_as_zeros);
aml_append(field, aml_reserved_field(160 /* bits, Offset(20) */));
aml_append(field, /* 1 if enabled, read only */
aml_named_field(stringify(MEMORY_SLOT_ENABLED), 1));
1. ACPI 5.1: 19.5.46 Field
>
> >
> >> Thanks,
> >> Zhu
> >>
> >>>> + dev = DEVICE(mdev->dimm);
> >>> potential NULL dereference, dimm could be NULL if guest does eject twice
> >>> or does eject of empty slot.
> >>> Perhaps add check before accessing dimm.
> >>>
> >>> if(!mdev->is_enabled) {
> >>> trace_..._ejecting_invalid_slot(...)
> >>> break;
> >>> }
> >>>
> >>>> + hotplug_ctrl = qdev_get_hotplug_handler(dev);
> >>>> + /* Call pc-dimm unplug cb. */
> >>>> + hotplug_handler_unplug(hotplug_ctrl, dev, NULL);
> >>> It's not that we can do anything about error at this point
> >>> but instead of forgetting it silently at least log error in trace,
> >>> the best would be in addition to that send QMP event to notify mgmt
> >>> about it. (sending QMP event could be a separate patch)
> >>>
> >>>
> >>>> }
> >>>> break;
> >>>> + default:
> >>>> + break;
> >>>> }
> >>>>
> >>>> }
> >>>>
> >> [...]
> > .
> >
>
