[RFC PATCH kernel v2] powerpc/powernv: Isolate NVLinks between GV100GL on Witherspoon
Alex Williamson
alex.williamson at redhat.com
Fri Apr 5 07:22:25 AEDT 2019
On Thu, 4 Apr 2019 16:23:24 +1100
Alexey Kardashevskiy <aik at ozlabs.ru> wrote:
> The NVIDIA V100 SXM2 GPUs are connected to the CPU via PCIe links and
> (on POWER9) NVLinks. In addition to that, GPUs themselves have direct
> peer to peer NVLinks in groups of 2 to 4 GPUs. At the moment the POWERNV
> platform puts all interconnected GPUs to the same IOMMU group.
>
> However the user may want to pass individual GPUs to the userspace so
> in order to do so we need to put them into separate IOMMU groups and
> cut off the interconnects.
>
> Thankfully V100 GPUs implement an interface to do by programming link
> disabling mask to BAR0 of a GPU. Once a link is disabled in a GPU using
> this interface, it cannot be re-enabled until the secondary bus reset is
> issued to the GPU.
>
> This adds an extra step to the secondary bus reset handler (the one used
> for such GPUs) to block NVLinks to GPUs which do not belong to the same
> group as the GPU being reset.
>
> This adds a new "isolate_nvlink" kernel parameter to allow GPU isolation;
> when enabled, every GPU gets its own IOMMU group. The new parameter is off
> by default to preserve the existing behaviour.
>
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> ---
> Changes:
> v2:
> * this is rework of [PATCH kernel RFC 0/2] vfio, powerpc/powernv: Isolate GV100GL
> but this time it is contained in the powernv platform
> ---
> arch/powerpc/platforms/powernv/Makefile | 2 +-
> arch/powerpc/platforms/powernv/pci.h | 1 +
> arch/powerpc/platforms/powernv/eeh-powernv.c | 1 +
> arch/powerpc/platforms/powernv/npu-dma.c | 24 +++-
> arch/powerpc/platforms/powernv/nvlinkgpu.c | 131 +++++++++++++++++++
> 5 files changed, 156 insertions(+), 3 deletions(-)
> create mode 100644 arch/powerpc/platforms/powernv/nvlinkgpu.c
>
> diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
> index da2e99efbd04..60a10d3b36eb 100644
> --- a/arch/powerpc/platforms/powernv/Makefile
> +++ b/arch/powerpc/platforms/powernv/Makefile
> @@ -6,7 +6,7 @@ obj-y += opal-msglog.o opal-hmi.o opal-power.o opal-irqchip.o
> obj-y += opal-kmsg.o opal-powercap.o opal-psr.o opal-sensor-groups.o
>
> obj-$(CONFIG_SMP) += smp.o subcore.o subcore-asm.o
> -obj-$(CONFIG_PCI) += pci.o pci-ioda.o npu-dma.o pci-ioda-tce.o
> +obj-$(CONFIG_PCI) += pci.o pci-ioda.o npu-dma.o pci-ioda-tce.o nvlinkgpu.o
> obj-$(CONFIG_CXL_BASE) += pci-cxl.o
> obj-$(CONFIG_EEH) += eeh-powernv.o
> obj-$(CONFIG_PPC_SCOM) += opal-xscom.o
> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
> index 8e36da379252..9fd3f391482c 100644
> --- a/arch/powerpc/platforms/powernv/pci.h
> +++ b/arch/powerpc/platforms/powernv/pci.h
> @@ -250,5 +250,6 @@ extern void pnv_pci_unlink_table_and_group(struct iommu_table *tbl,
> extern void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
> void *tce_mem, u64 tce_size,
> u64 dma_offset, unsigned int page_shift);
> +extern void pnv_try_isolate_nvidia_v100(struct pci_dev *gpdev);
>
> #endif /* __POWERNV_PCI_H */
> diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c
> index f38078976c5d..464b097d9635 100644
> --- a/arch/powerpc/platforms/powernv/eeh-powernv.c
> +++ b/arch/powerpc/platforms/powernv/eeh-powernv.c
> @@ -937,6 +937,7 @@ void pnv_pci_reset_secondary_bus(struct pci_dev *dev)
> pnv_eeh_bridge_reset(dev, EEH_RESET_HOT);
> pnv_eeh_bridge_reset(dev, EEH_RESET_DEACTIVATE);
> }
> + pnv_try_isolate_nvidia_v100(dev);
> }
>
> static void pnv_eeh_wait_for_pending(struct pci_dn *pdn, const char *type,
> diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
> index dc23d9d2a7d9..017eae8197e7 100644
> --- a/arch/powerpc/platforms/powernv/npu-dma.c
> +++ b/arch/powerpc/platforms/powernv/npu-dma.c
> @@ -529,6 +529,23 @@ static void pnv_comp_attach_table_group(struct npu_comp *npucomp,
> ++npucomp->pe_num;
> }
>
> +static bool isolate_nvlink;
> +
> +static int __init parse_isolate_nvlink(char *p)
> +{
> + bool val;
> +
> + if (!p)
> + val = true;
> + else if (kstrtobool(p, &val))
> + return -EINVAL;
> +
> + isolate_nvlink = val;
> +
> + return 0;
> +}
> +early_param("isolate_nvlink", parse_isolate_nvlink);
> +
> struct iommu_table_group *pnv_try_setup_npu_table_group(struct pnv_ioda_pe *pe)
> {
> struct iommu_table_group *table_group;
> @@ -549,7 +566,7 @@ struct iommu_table_group *pnv_try_setup_npu_table_group(struct pnv_ioda_pe *pe)
>
> hose = pci_bus_to_host(npdev->bus);
>
> - if (hose->npu) {
> + if (hose->npu && !isolate_nvlink) {
> table_group = &hose->npu->npucomp.table_group;
>
> if (!table_group->group) {
> @@ -559,7 +576,10 @@ struct iommu_table_group *pnv_try_setup_npu_table_group(struct pnv_ioda_pe *pe)
> pe->pe_number);
> }
> } else {
> - /* Create a group for 1 GPU and attached NPUs for POWER8 */
> + /*
> + * Create a group for 1 GPU and attached NPUs for
> + * POWER8 (always) or POWER9 (when isolate_nvlink).
> + */
> pe->npucomp = kzalloc(sizeof(*pe->npucomp), GFP_KERNEL);
> table_group = &pe->npucomp->table_group;
> table_group->ops = &pnv_npu_peers_ops;
> diff --git a/arch/powerpc/platforms/powernv/nvlinkgpu.c b/arch/powerpc/platforms/powernv/nvlinkgpu.c
> new file mode 100644
> index 000000000000..dbd8e9d47a05
> --- /dev/null
> +++ b/arch/powerpc/platforms/powernv/nvlinkgpu.c
> @@ -0,0 +1,131 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * A helper to disable NVLinks between GPUs on IBM Withersponn platform.
> + *
> + * Copyright (C) 2019 IBM Corp. All rights reserved.
> + * Author: Alexey Kardashevskiy <aik at ozlabs.ru>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/of.h>
> +#include <linux/iommu.h>
> +#include <linux/pci.h>
> +
> +static int nvlinkgpu_is_ph_in_group(struct device *dev, void *data)
> +{
> + return dev->of_node->phandle == *(phandle *) data;
> +}
> +
> +static u32 nvlinkgpu_get_disable_mask(struct device *dev)
> +{
> + int npu, peer;
> + u32 mask;
> + struct device_node *dn;
> + struct iommu_group *group;
> +
> + dn = dev->of_node;
> + if (!of_find_property(dn, "ibm,nvlink-peers", NULL))
> + return 0;
> +
> + group = iommu_group_get(dev);
> + if (!group)
> + return 0;
> +
> + /*
> + * Collect links to keep which includes links to NPU and links to
> + * other GPUs in the same IOMMU group.
> + */
> + for (npu = 0, mask = 0; ; ++npu) {
> + u32 npuph = 0;
> +
> + if (of_property_read_u32_index(dn, "ibm,npu", npu, &npuph))
> + break;
> +
> + for (peer = 0; ; ++peer) {
> + u32 peerph = 0;
> +
> + if (of_property_read_u32_index(dn, "ibm,nvlink-peers",
> + peer, &peerph))
> + break;
> +
> + if (peerph != npuph &&
> + !iommu_group_for_each_dev(group, &peerph,
> + nvlinkgpu_is_ph_in_group))
> + continue;
> +
> + mask |= 1 << (peer + 16);
> + }
> + }
> + iommu_group_put(group);
> +
> + /* Disabling mechanism takes links to disable so invert it here */
> + mask = ~mask & 0x3F0000;
> +
> + return mask;
> +}
> +
> +void pnv_try_isolate_nvidia_v100(struct pci_dev *bridge)
> +{
> + u32 mask;
> + void __iomem *bar0_0, *bar0_120000, *bar0_a00000;
> + struct pci_dev *pdev;
> +
> + if (!bridge->subordinate)
> + return;
> +
> + pdev = list_first_entry_or_null(&bridge->subordinate->devices,
> + struct pci_dev, bus_list);
> + if (!pdev)
> + return;
> +
> + if (pdev->vendor != PCI_VENDOR_ID_NVIDIA)
> + return;
> +
> + mask = nvlinkgpu_get_disable_mask(&pdev->dev);
> + if (!mask)
> + return;
> +
> + bar0_0 = pci_iomap_range(pdev, 0, 0, 0x10000);
> + bar0_120000 = pci_iomap_range(pdev, 0, 0x120000, 0x10000);
> + bar0_a00000 = pci_iomap_range(pdev, 0, 0xA00000, 0x10000);
> +
> + if (bar0_120000 && bar0_0 && bar0_a00000) {
> + u32 val;
> + u16 cmd = 0, cmdmask = PCI_COMMAND_MEMORY;
> +
> + pci_restore_state(pdev);
> + pci_read_config_word(pdev, PCI_COMMAND, &cmd);
> + if ((cmd & cmdmask) != cmdmask)
> + pci_write_config_word(pdev, PCI_COMMAND, cmd | cmdmask);
> +
> + /*
> + * The sequence is from "Tesla P100 and V100 SXM2 NVLink
> + * Isolation on Multi-Tenant Systems".
> + * The register names are not provided there either,
> + * hence raw values.
> + */
> + iowrite32(0x4, bar0_120000 + 0x4C);
> + iowrite32(0x2, bar0_120000 + 0x2204);
> + val = ioread32(bar0_0 + 0x200);
> + val |= 0x02000000;
> + iowrite32(val, bar0_0 + 0x200);
> + val = ioread32(bar0_a00000 + 0x148);
> + val |= mask;
> + iowrite32(val, bar0_a00000 + 0x148);
> +
> + if ((cmd | cmdmask) != cmd)
> + pci_write_config_word(pdev, PCI_COMMAND, cmd);
> + }
> +
It's a little troubling that if something goes wrong with an iomap
we'll silently fail to re-enable the expected isolation. Seems worthy
of at least a pci_warn/err. Thanks,
Alex
> + if (bar0_0)
> + pci_iounmap(pdev, bar0_0);
> + if (bar0_120000)
> + pci_iounmap(pdev, bar0_120000);
> + if (bar0_a00000)
> + pci_iounmap(pdev, bar0_a00000);
> +}
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