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Re: [Qemu-devel] [RFC PATCH 0/4] ARM virt: ACPI memory hotplug support

From: Laszlo Ersek
Subject: Re: [Qemu-devel] [RFC PATCH 0/4] ARM virt: ACPI memory hotplug support
Date: Fri, 22 Feb 2019 20:11:29 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1

On 02/22/19 17:03, Auger Eric wrote:
> Hi Shameer,
> On 1/28/19 12:05 PM, Shameer Kolothum wrote:
>> This series is an attempt to provide hotplug support to both
>> pc-dimm and nvdimm device memory on ARM virt platform. This is
>> based on Eric's recent works to support PCDIMM/NVDIMM device memory[1].
>> The kernel support for arm64 memory hot add was added only
>> recently by Robin[2] and hence the guest kernel should be => 5.0-rc1.
>> This makes use of PL061 GPIO controller to sent related ACPI events
> s/sent/send
>> to the Guest. The only reference I could find with respect to the GPIO
>> pins usage is here[3] which says, "use PIN 3 for system_powerdown,
>> reserving PIN 0, 1, 2 for PCI hotplug, CPU hotplug and memory hotplug".
>> Hence Pin 2 is used for PCDIMM and pin 4 for NVDIMM.
>> This is sanity tested on a HiSilicon ARM64 platform and appreciate
>> any further testing.
> I did some testing on another platform and I got the exactly the same
> results as yours: PCDIMM hot plug works fine. Also after system_reset I
> still can see the slots.
> Hot-unplug is not supported though.
> For NVDIMM, hot-add works fine and and I can see the slots using ndctl
> on guest. But after system_reset, the guest does not boot properly.
>> This series can be applied on top of Eric's branch here[4]
>> Test:
>> ------
>> Please use a Guest kernel image >5.0-rc1 with all the mem/nvdimm
>> hotplug related CONFIGs enabled.
>> ./qemu-system-aarch64 \
>> -machine virt,gic-version=3,nvdimm \
>> -m 1G,maxmem=4G,slots=4 \
>> -cpu host \
>> -kernel Image \
>> -initrd rootfs-iperf.cpio \
>> -bios QEMU_EFI.fd \
>> -numa node,nodeid=0 \
>> -net none \
>> -nographic -enable-kvm \
>> -append "console=ttyAMA0 acpi=force earlycon=pl011,0x9000000"
>> Enter Qemu monitor,
>> Add pc-dimm:
>> object_add memory-backend-ram,id=mem1,size=1G
>> device_add pc-dimm,id=dimm1,memdev=mem1
>> Add nvdimm:
>> object_add memory-backend-ram,id=mem2,size=1G
>> device_add nvdimm,id=dimm2,memdev=mem2
>> Known Issue:
>> It is observed that hot adding nvdimm will results in guest reboot
>> failure. EDK2 fails to build the ACPI tables on reboot. Please find
>> below EDK2 log on Guest reboot after nvdimm hot-add,
>> ProcessCmdAddChecksum: invalid checksum range in "etc/acpi/tables"
>> OnRootBridgesConnected: InstallAcpiTables: Protocol Error
>> The root cause seems to be EDK2 ACPI table checksum failure
>> as NFIT table is getting updated on hot-add. This needs further
>> investigation.
> + Ard, Leif, Laszlo if they have any idea of what is missing/wrong.

Huh, very interesting; I usually don't expect my sanity checks to fire
in practice. :)

The message

  ProcessCmdAddChecksum: invalid checksum range in "etc/acpi/tables"

is logged by OVMF's and ArmVirtQemu's ACPI Platform DXE Driver when it
finds an invalid COMMAND_ADD_CHECKSUM command in QEMU's ACPI
linker/loader script.

Please see the command definition in QEMU's
"hw/acpi/bios-linker-loader.c". In particular, please refer to the
function bios_linker_loader_add_checksum(), which builds the command
structure, and documents the fields.

(You may also refer to QEMU_LOADER_ADD_CHECKSUM in file
"OvmfPkg/AcpiPlatformDxe/QemuLoader.h" in the edk2 source tree, for the
same information.)

The error message is logged if:
- the offset at which the checksum should be stored falls outside of the
size of the fw_cfg blob, or
- the range over which the checksum should be calculated falls outside
(at least in part) of the fw_cfg blob.

To me this suggests that QEMU generates an invalid COMMAND_ADD_CHECKSUM
command for the firmware.

... I've tried to skim the patches briefly. I think there must be an
error in the DSDT building logic that is only active on reboot if an
nvdimm module was hot-added before the reboot.


>> [1]https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg05740.html
>> [2]https://patchwork.kernel.org/patch/10724455/
>> [3]https://lists.gnu.org/archive/html/qemu-arm/2015-12/msg00095.html
>> [4]https://github.com/eauger/qemu/tree/v3.1.0-dimm-v5
>> Shameer Kolothum (4):
>>   hw:acpi: Make ACPI IO address space configurable
>>   hw/arm/virt: Add GPIO based pcdimm hotplug ACPI event support
>>   hw/arm/virt: Enable pc-dimm hotplug support
>>   hw/arm/virt: Add nvdimm hotplug support
>>  default-configs/arm-softmmu.mak  |   1 +
>>  hw/acpi/memory_hotplug.c         |  13 +++--
>>  hw/arm/virt-acpi-build.c         |  45 +++++++++++++++--
>>  hw/arm/virt.c                    | 105 
>> ++++++++++++++++++++++++++++++++++++---
>>  hw/i386/acpi-build.c             |   3 +-
>>  include/hw/acpi/memory_hotplug.h |   6 ++-
>>  include/hw/arm/virt.h            |  15 ++++++
>>  7 files changed, 168 insertions(+), 20 deletions(-)

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