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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/gpu/rfc/i915_vm_bind.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/gpu/rfc/i915_vm_bind.rst')
-rw-r--r-- | Documentation/gpu/rfc/i915_vm_bind.rst | 245 |
1 files changed, 245 insertions, 0 deletions
diff --git a/Documentation/gpu/rfc/i915_vm_bind.rst b/Documentation/gpu/rfc/i915_vm_bind.rst new file mode 100644 index 000000000..9a1dcdf27 --- /dev/null +++ b/Documentation/gpu/rfc/i915_vm_bind.rst @@ -0,0 +1,245 @@ +========================================== +I915 VM_BIND feature design and use cases +========================================== + +VM_BIND feature +================ +DRM_I915_GEM_VM_BIND/UNBIND ioctls allows UMD to bind/unbind GEM buffer +objects (BOs) or sections of a BOs at specified GPU virtual addresses on a +specified address space (VM). These mappings (also referred to as persistent +mappings) will be persistent across multiple GPU submissions (execbuf calls) +issued by the UMD, without user having to provide a list of all required +mappings during each submission (as required by older execbuf mode). + +The VM_BIND/UNBIND calls allow UMDs to request a timeline out fence for +signaling the completion of bind/unbind operation. + +VM_BIND feature is advertised to user via I915_PARAM_VM_BIND_VERSION. +User has to opt-in for VM_BIND mode of binding for an address space (VM) +during VM creation time via I915_VM_CREATE_FLAGS_USE_VM_BIND extension. + +VM_BIND/UNBIND ioctl calls executed on different CPU threads concurrently are +not ordered. Furthermore, parts of the VM_BIND/UNBIND operations can be done +asynchronously, when valid out fence is specified. + +VM_BIND features include: + +* Multiple Virtual Address (VA) mappings can map to the same physical pages + of an object (aliasing). +* VA mapping can map to a partial section of the BO (partial binding). +* Support capture of persistent mappings in the dump upon GPU error. +* Support for userptr gem objects (no special uapi is required for this). + +TLB flush consideration +------------------------ +The i915 driver flushes the TLB for each submission and when an object's +pages are released. The VM_BIND/UNBIND operation will not do any additional +TLB flush. Any VM_BIND mapping added will be in the working set for subsequent +submissions on that VM and will not be in the working set for currently running +batches (which would require additional TLB flushes, which is not supported). + +Execbuf ioctl in VM_BIND mode +------------------------------- +A VM in VM_BIND mode will not support older execbuf mode of binding. +The execbuf ioctl handling in VM_BIND mode differs significantly from the +older execbuf2 ioctl (See struct drm_i915_gem_execbuffer2). +Hence, a new execbuf3 ioctl has been added to support VM_BIND mode. (See +struct drm_i915_gem_execbuffer3). The execbuf3 ioctl will not accept any +execlist. Hence, no support for implicit sync. It is expected that the below +work will be able to support requirements of object dependency setting in all +use cases: + +"dma-buf: Add an API for exporting sync files" +(https://lwn.net/Articles/859290/) + +The new execbuf3 ioctl only works in VM_BIND mode and the VM_BIND mode only +works with execbuf3 ioctl for submission. All BOs mapped on that VM (through +VM_BIND call) at the time of execbuf3 call are deemed required for that +submission. + +The execbuf3 ioctl directly specifies the batch addresses instead of as +object handles as in execbuf2 ioctl. The execbuf3 ioctl will also not +support many of the older features like in/out/submit fences, fence array, +default gem context and many more (See struct drm_i915_gem_execbuffer3). + +In VM_BIND mode, VA allocation is completely managed by the user instead of +the i915 driver. Hence all VA assignment, eviction are not applicable in +VM_BIND mode. Also, for determining object activeness, VM_BIND mode will not +be using the i915_vma active reference tracking. It will instead use dma-resv +object for that (See `VM_BIND dma_resv usage`_). + +So, a lot of existing code supporting execbuf2 ioctl, like relocations, VA +evictions, vma lookup table, implicit sync, vma active reference tracking etc., +are not applicable for execbuf3 ioctl. Hence, all execbuf3 specific handling +should be in a separate file and only functionalities common to these ioctls +can be the shared code where possible. + +VM_PRIVATE objects +------------------- +By default, BOs can be mapped on multiple VMs and can also be dma-buf +exported. Hence these BOs are referred to as Shared BOs. +During each execbuf submission, the request fence must be added to the +dma-resv fence list of all shared BOs mapped on the VM. + +VM_BIND feature introduces an optimization where user can create BO which +is private to a specified VM via I915_GEM_CREATE_EXT_VM_PRIVATE flag during +BO creation. Unlike Shared BOs, these VM private BOs can only be mapped on +the VM they are private to and can't be dma-buf exported. +All private BOs of a VM share the dma-resv object. Hence during each execbuf +submission, they need only one dma-resv fence list updated. Thus, the fast +path (where required mappings are already bound) submission latency is O(1) +w.r.t the number of VM private BOs. + +VM_BIND locking hirarchy +------------------------- +The locking design here supports the older (execlist based) execbuf mode, the +newer VM_BIND mode, the VM_BIND mode with GPU page faults and possible future +system allocator support (See `Shared Virtual Memory (SVM) support`_). +The older execbuf mode and the newer VM_BIND mode without page faults manages +residency of backing storage using dma_fence. The VM_BIND mode with page faults +and the system allocator support do not use any dma_fence at all. + +VM_BIND locking order is as below. + +1) Lock-A: A vm_bind mutex will protect vm_bind lists. This lock is taken in + vm_bind/vm_unbind ioctl calls, in the execbuf path and while releasing the + mapping. + + In future, when GPU page faults are supported, we can potentially use a + rwsem instead, so that multiple page fault handlers can take the read side + lock to lookup the mapping and hence can run in parallel. + The older execbuf mode of binding do not need this lock. + +2) Lock-B: The object's dma-resv lock will protect i915_vma state and needs to + be held while binding/unbinding a vma in the async worker and while updating + dma-resv fence list of an object. Note that private BOs of a VM will all + share a dma-resv object. + + The future system allocator support will use the HMM prescribed locking + instead. + +3) Lock-C: Spinlock/s to protect some of the VM's lists like the list of + invalidated vmas (due to eviction and userptr invalidation) etc. + +When GPU page faults are supported, the execbuf path do not take any of these +locks. There we will simply smash the new batch buffer address into the ring and +then tell the scheduler run that. The lock taking only happens from the page +fault handler, where we take lock-A in read mode, whichever lock-B we need to +find the backing storage (dma_resv lock for gem objects, and hmm/core mm for +system allocator) and some additional locks (lock-D) for taking care of page +table races. Page fault mode should not need to ever manipulate the vm lists, +so won't ever need lock-C. + +VM_BIND LRU handling +--------------------- +We need to ensure VM_BIND mapped objects are properly LRU tagged to avoid +performance degradation. We will also need support for bulk LRU movement of +VM_BIND objects to avoid additional latencies in execbuf path. + +The page table pages are similar to VM_BIND mapped objects (See +`Evictable page table allocations`_) and are maintained per VM and needs to +be pinned in memory when VM is made active (ie., upon an execbuf call with +that VM). So, bulk LRU movement of page table pages is also needed. + +VM_BIND dma_resv usage +----------------------- +Fences needs to be added to all VM_BIND mapped objects. During each execbuf +submission, they are added with DMA_RESV_USAGE_BOOKKEEP usage to prevent +over sync (See enum dma_resv_usage). One can override it with either +DMA_RESV_USAGE_READ or DMA_RESV_USAGE_WRITE usage during explicit object +dependency setting. + +Note that DRM_I915_GEM_WAIT and DRM_I915_GEM_BUSY ioctls do not check for +DMA_RESV_USAGE_BOOKKEEP usage and hence should not be used for end of batch +check. Instead, the execbuf3 out fence should be used for end of batch check +(See struct drm_i915_gem_execbuffer3). + +Also, in VM_BIND mode, use dma-resv apis for determining object activeness +(See dma_resv_test_signaled() and dma_resv_wait_timeout()) and do not use the +older i915_vma active reference tracking which is deprecated. This should be +easier to get it working with the current TTM backend. + +Mesa use case +-------------- +VM_BIND can potentially reduce the CPU overhead in Mesa (both Vulkan and Iris), +hence improving performance of CPU-bound applications. It also allows us to +implement Vulkan's Sparse Resources. With increasing GPU hardware performance, +reducing CPU overhead becomes more impactful. + + +Other VM_BIND use cases +======================== + +Long running Compute contexts +------------------------------ +Usage of dma-fence expects that they complete in reasonable amount of time. +Compute on the other hand can be long running. Hence it is appropriate for +compute to use user/memory fence (See `User/Memory Fence`_) and dma-fence usage +must be limited to in-kernel consumption only. + +Where GPU page faults are not available, kernel driver upon buffer invalidation +will initiate a suspend (preemption) of long running context, finish the +invalidation, revalidate the BO and then resume the compute context. This is +done by having a per-context preempt fence which is enabled when someone tries +to wait on it and triggers the context preemption. + +User/Memory Fence +~~~~~~~~~~~~~~~~~~ +User/Memory fence is a <address, value> pair. To signal the user fence, the +specified value will be written at the specified virtual address and wakeup the +waiting process. User fence can be signaled either by the GPU or kernel async +worker (like upon bind completion). User can wait on a user fence with a new +user fence wait ioctl. + +Here is some prior work on this: +https://patchwork.freedesktop.org/patch/349417/ + +Low Latency Submission +~~~~~~~~~~~~~~~~~~~~~~~ +Allows compute UMD to directly submit GPU jobs instead of through execbuf +ioctl. This is made possible by VM_BIND is not being synchronized against +execbuf. VM_BIND allows bind/unbind of mappings required for the directly +submitted jobs. + +Debugger +--------- +With debug event interface user space process (debugger) is able to keep track +of and act upon resources created by another process (debugged) and attached +to GPU via vm_bind interface. + +GPU page faults +---------------- +GPU page faults when supported (in future), will only be supported in the +VM_BIND mode. While both the older execbuf mode and the newer VM_BIND mode of +binding will require using dma-fence to ensure residency, the GPU page faults +mode when supported, will not use any dma-fence as residency is purely managed +by installing and removing/invalidating page table entries. + +Page level hints settings +-------------------------- +VM_BIND allows any hints setting per mapping instead of per BO. Possible hints +include placement and atomicity. Sub-BO level placement hint will be even more +relevant with upcoming GPU on-demand page fault support. + +Page level Cache/CLOS settings +------------------------------- +VM_BIND allows cache/CLOS settings per mapping instead of per BO. + +Evictable page table allocations +--------------------------------- +Make pagetable allocations evictable and manage them similar to VM_BIND +mapped objects. Page table pages are similar to persistent mappings of a +VM (difference here are that the page table pages will not have an i915_vma +structure and after swapping pages back in, parent page link needs to be +updated). + +Shared Virtual Memory (SVM) support +------------------------------------ +VM_BIND interface can be used to map system memory directly (without gem BO +abstraction) using the HMM interface. SVM is only supported with GPU page +faults enabled. + +VM_BIND UAPI +============= + +.. kernel-doc:: Documentation/gpu/rfc/i915_vm_bind.h |