Re: [PATCH v8 1/2] qom: new object to associate device to NUMA node

[Jonathan Cameron]

On Wed, 6 Mar 2024 12:33:16 +0000
<ankita@nvidia.com> wrote:

> From: Ankit Agrawal <ankita@nvidia.com>
> 
> NVIDIA GPU's support MIG (Mult-Instance GPUs) feature [1], which allows
> partitioning of the GPU device resources (including device memory) into
> several (upto 8) isolated instances. Each of the partitioned memory needs
> a dedicated NUMA node to operate. The partitions are not fixed and they
> can be created/deleted at runtime.
> 
> Unfortunately Linux OS does not provide a means to dynamically create/destroy
> NUMA nodes and such feature implementation is not expected to be trivial. The
> nodes that OS discovers at the boot time while parsing SRAT remains fixed. So
> we utilize the Generic Initiator Affinity structures that allows association
> between nodes and devices. Multiple GI structures per BDF is possible,
> allowing creation of multiple nodes by exposing unique PXM in each of these
> structures.
> 
> Implement the mechanism to build the GI affinity structures as Qemu currently
> does not. Introduce a new acpi-generic-initiator object to allow host admin
> link a device with an associated NUMA node. Qemu maintains this association
> and use this object to build the requisite GI Affinity Structure.
> 
> When multiple NUMA nodes are associated with a device, it is required to
> create those many number of acpi-generic-initiator objects, each representing
> a unique device:node association.
> 
> Following is one of a decoded GI affinity structure in VM ACPI SRAT.
> [0C8h 0200   1]                Subtable Type : 05 [Generic Initiator Affinity]
> [0C9h 0201   1]                       Length : 20
> 
> [0CAh 0202   1]                    Reserved1 : 00
> [0CBh 0203   1]           Device Handle Type : 01
> [0CCh 0204   4]             Proximity Domain : 00000007
> [0D0h 0208  16]                Device Handle : 00 00 20 00 00 00 00 00 00 00 
> 00
> 00 00 00 00 00
> [0E0h 0224   4]        Flags (decoded below) : 00000001
>                                      Enabled : 1
> [0E4h 0228   4]                    Reserved2 : 00000000
> 
> [0E8h 0232   1]                Subtable Type : 05 [Generic Initiator Affinity]
> [0E9h 0233   1]                       Length : 20
> 
> An admin can provide a range of acpi-generic-initiator objects, each
> associating a device (by providing the id through pci-dev argument)
> to the desired NUMA node (using the node argument). Currently, only PCI
> device is supported.
> 
> For the grace hopper system, create a range of 8 nodes and associate that
> with the device using the acpi-generic-initiator object. While a configuration
> of less than 8 nodes per device is allowed, such configuration will prevent
> utilization of the feature to the fullest. The following sample creates 8
> nodes per PCI device for a VM with 2 PCI devices and link them to the
> respecitve PCI device using acpi-generic-initiator objects:
> 
> -numa node,nodeid=2 -numa node,nodeid=3 -numa node,nodeid=4 \
> -numa node,nodeid=5 -numa node,nodeid=6 -numa node,nodeid=7 \
> -numa node,nodeid=8 -numa node,nodeid=9 \
> -device 
> vfio-pci-nohotplug,host=0009:01:00.0,bus=pcie.0,addr=04.0,rombar=0,id=dev0 \
> -object acpi-generic-initiator,id=gi0,pci-dev=dev0,node=2 \
> -object acpi-generic-initiator,id=gi1,pci-dev=dev0,node=3 \
> -object acpi-generic-initiator,id=gi2,pci-dev=dev0,node=4 \
> -object acpi-generic-initiator,id=gi3,pci-dev=dev0,node=5 \
> -object acpi-generic-initiator,id=gi4,pci-dev=dev0,node=6 \
> -object acpi-generic-initiator,id=gi5,pci-dev=dev0,node=7 \
> -object acpi-generic-initiator,id=gi6,pci-dev=dev0,node=8 \
> -object acpi-generic-initiator,id=gi7,pci-dev=dev0,node=9 \
> 
> -numa node,nodeid=10 -numa node,nodeid=11 -numa node,nodeid=12 \
> -numa node,nodeid=13 -numa node,nodeid=14 -numa node,nodeid=15 \
> -numa node,nodeid=16 -numa node,nodeid=17 \
> -device 
> vfio-pci-nohotplug,host=0009:01:01.0,bus=pcie.0,addr=05.0,rombar=0,id=dev1 \
> -object acpi-generic-initiator,id=gi8,pci-dev=dev1,node=10 \
> -object acpi-generic-initiator,id=gi9,pci-dev=dev1,node=11 \
> -object acpi-generic-initiator,id=gi10,pci-dev=dev1,node=12 \
> -object acpi-generic-initiator,id=gi11,pci-dev=dev1,node=13 \
> -object acpi-generic-initiator,id=gi12,pci-dev=dev1,node=14 \
> -object acpi-generic-initiator,id=gi13,pci-dev=dev1,node=15 \
> -object acpi-generic-initiator,id=gi14,pci-dev=dev1,node=16 \
> -object acpi-generic-initiator,id=gi15,pci-dev=dev1,node=17 \
> 
> The performance benefits can be realized by providing the NUMA node distances
> appropriately (through libvirt tags or Qemu params). The admin can get the
> distance among nodes in hardware using `numactl -H`.

That's a lot of description when you could just have claimed you want a normal
GI node for HMAT and we'd have all believed you ;)

> 
> Link: https://www.nvidia.com/en-in/technologies/multi-instance-gpu [1]
> Cc: Jonathan Cameron <qemu-devel@nongnu.org>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Markus Armbruster <armbru@redhat.com>
> Acked-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Ankit Agrawal <ankita@nvidia.com>

Hi Ankit,

Some minor things inline. With the includes tidied up.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> diff --git a/include/hw/acpi/acpi_generic_initiator.h 
> b/include/hw/acpi/acpi_generic_initiator.h
> new file mode 100644
> index 0000000000..23d0b591c6
> --- /dev/null
> +++ b/include/hw/acpi/acpi_generic_initiator.h
> @@ -0,0 +1,32 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES. All rights reserved
> + */
> +
> +#ifndef ACPI_GENERIC_INITIATOR_H
> +#define ACPI_GENERIC_INITIATOR_H
> +
> +#include "hw/mem/pc-dimm.h"

Why?

> +#include "hw/acpi/bios-linker-loader.h"
> +#include "hw/acpi/aml-build.h"
> +#include "sysemu/numa.h"

This should only include headers that it uses directly.
If they are needed down in the c files, then include them there.

Most of these are not related to what you have here.

> +#include "qemu/uuid.h"
> +#include "qom/object.h"
> +#include "qom/object_interfaces.h"
> +
> +#define TYPE_ACPI_GENERIC_INITIATOR "acpi-generic-initiator"
> +
> +typedef struct AcpiGenericInitiator {
> +    /* private */
> +    Object parent;
> +
> +    /* public */
> +    char *pci_dev;
> +    uint16_t node;
> +} AcpiGenericInitiator;
> +
> +typedef struct AcpiGenericInitiatorClass {
> +    ObjectClass parent_class;
> +} AcpiGenericInitiatorClass;

Trivial, but you could push the class definition down into the c file
given it's not accessed from anywhere else.

> +
> +#endif