From f146c7bc85a51f95c05e0f8173d484eb301ece78 Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Thu, 13 Aug 2026 18:52:04 +0200 Subject: PCI: Add pci_irq_type() to query the allocated interrupt type Add a helper that returns PCI_IRQ_MSIX, PCI_IRQ_MSI, or PCI_IRQ_INTX based on the interrupt type the PCI core selected after pci_alloc_irq_vectors(). Several drivers already open-code this check against pdev->msix_enabled and pdev->msi_enabled, or even open code this helper [1]. A common helper avoids the duplication and keeps drivers from accessing the bitfield directly (see also [2]). Acked-by: Bjorn Helgaas Tested-by: John Hubbard Link: https://elixir.bootlin.com/linux/v7.1/source/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c#L196 [1] Inspired-by: John Hubbard Link: https://lore.kernel.org/all/DKKG2QM3YJYB.Z2H2B2UXJ75N@kernel.org/ [2] Reviewed-by: Gary Guo Link: https://patch.msgid.link/20260813165234.620555-5-dakr@kernel.org [ Add missing pci_irq_type() stub for CONFIG_PCI=n. ] Signed-off-by: Danilo Krummrich --- Documentation/gpu/drm-compute.rst | 54 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 Documentation/gpu/drm-compute.rst (limited to 'Documentation/gpu/drm-compute.rst') diff --git a/Documentation/gpu/drm-compute.rst b/Documentation/gpu/drm-compute.rst new file mode 100644 index 000000000..f90c3e63a --- /dev/null +++ b/Documentation/gpu/drm-compute.rst @@ -0,0 +1,54 @@ +================================== +Long running workloads and compute +================================== + +Long running workloads (compute) are workloads that will not complete in 10 +seconds. (The time let the user wait before he reaches for the power button). +This means that other techniques need to be used to manage those workloads, +that cannot use fences. + +Some hardware may schedule compute jobs, and have no way to pre-empt them, or +have their memory swapped out from them. Or they simply want their workload +not to be preempted or swapped out at all. + +This means that it differs from what is described in driver-api/dma-buf.rst. + +As with normal compute jobs, dma-fence may not be used at all. In this case, +not even to force preemption. The driver with is simply forced to unmap a BO +from the long compute job's address space on unbind immediately, not even +waiting for the workload to complete. Effectively this terminates the workload +when there is no hardware support to recover. + +Since this is undesirable, there need to be mitigations to prevent a workload +from being terminated. There are several possible approach, all with their +advantages and drawbacks. + +The first approach you will likely try is to pin all buffers used by compute. +This guarantees that the job will run uninterrupted, but also allows a very +denial of service attack by pinning as much memory as possible, hogging the +all GPU memory, and possibly a huge chunk of CPU memory. + +A second approach that will work slightly better on its own is adding an option +not to evict when creating a new job (any kind). If all of userspace opts in +to this flag, it would prevent cooperating userspace from forced terminating +older compute jobs to start a new one. + +If job preemption and recoverable pagefaults are not available, those are the +only approaches possible. So even with those, you want a separate way of +controlling resources. The standard kernel way of doing so is cgroups. + +This creates a third option, using cgroups to prevent eviction. Both GPU and +driver-allocated CPU memory would be accounted to the correct cgroup, and +eviction would be made cgroup aware. This allows the GPU to be partitioned +into cgroups, that will allow jobs to run next to each other without +interference. + +The interface to the cgroup would be similar to the current CPU memory +interface, with similar semantics for min/low/high/max, if eviction can +be made cgroup aware. + +What should be noted is that each memory region (tiled memory for example) +should have its own accounting. + +The key is set to the regionid set by the driver, for example "tile0". +For the value of $card, we use drmGetUnique(). -- cgit v1.3.1