ACK/Cmnt: [SRU][N][PATCH v2 0/3] Backport pci=config_acs parameter with fix commit

[Edoardo Canepa]

On 19/05/25 16:07, Jacob Martin wrote:
> BugLink: https://bugs.launchpad.net/bugs/2100340
>
> SRU Justification:
>
> [Impact]
>
> The PCI ACS capability parameter is used to enable and configure access
> control between PCIe devices. In particular, this parameter can enable
> and/or restrict peer-to-peer traffic between so-configured PCIe devices.
>
> For example, this parameter is necessary for GPUDirect RDMA
> applications, where peer-to-peer communication between a GPU and an
> RDMA-capable device is required. This parameter allows an administrator
> to configure the system for the specific level of isolation between PCIe
> devices required to enable this feature for their use case.
>
> [Fix]
>
> This consists of clean cherry picks of commits 47c8846a49ba ("PCI:
> Extend ACS configurability"), f3c3ccc4fe49 ("PCI: Fix pci_enable_acs()
> support for the ACS quirks"), and 9cf8a952d57b ("PCI/ACS: Fix
> 'pci=config_acs=' parameter").
>
> [Test Plan]
>
> The patchset was tested on a DGX GH200 system by booting with the kernel
> parameter test cases described in the commit message of 9cf8a952d57b
> ("PCI/ACS: Fix 'pci=config_acs=' parameter").
>
> Multiple PCIe devices could be configured with the pci=config_acs
> parameter as is expected with the fix commit, and pci=disable_acs_redir
> works as expected.
>
> $ cat /proc/cmdline
> BOOT_IMAGE=/boot/vmlinuz-6.8.0-1060-generic root=UUID=fe5d0b12-5ce2-4b59-b669-c1e1741fd483 ro ignore_loglevel "dyndbg=file drivers/pci/pci.c +p" pci=config_acs=1111011 at 0000:01:00.0;101xxxx at 0000:01:00.1
> $ sudo dmesg | grep ACS
> [    6.433520] pci 0000:01:00.0: ACS mask  = 0x007f
> [    6.438305] pci 0000:01:00.0: ACS flags = 0x007b
> [    6.443081] pci 0000:01:00.0: ACS control = 0x0000
> [    6.448037] pci 0000:01:00.0: ACS fw_ctrl = 0x0000
> [    6.452987] pci 0000:01:00.0: Configured ACS to 0x007b
> [    6.516083] pci 0000:01:00.1: ACS mask  = 0x0070
> [    6.520862] pci 0000:01:00.1: ACS flags = 0x0050
> [    6.525636] pci 0000:01:00.1: ACS control = 0x0000
> [    6.530590] pci 0000:01:00.1: ACS fw_ctrl = 0x0000
> [    6.535540] pci 0000:01:00.1: Configured ACS to 0x0050
>
> [Where problems could occur]
>
> This affects the pci=config_acs and pci=config_acs_redir kernel boot
> parameters. Issues could arise as malfunctioning of these two boot
> parameters, or as improper configuration of PCIe devices.
>
> [Other Info]
> v2:
> - drop Oracular patchset, patches were included in Oracular via stable updates
> - include fix commit f3c3ccc4fe49 ("PCI: Fix pci_enable_acs() support
>    for the ACS quirks")
>
> Jason Gunthorpe (1):
>    PCI: Fix pci_enable_acs() support for the ACS quirks
>
> Tushar Dave (1):
>    PCI/ACS: Fix 'pci=config_acs=' parameter
>
> Vidya Sagar (1):
>    PCI: Extend ACS configurability
>
>   .../admin-guide/kernel-parameters.txt         |  32 ++++
>   drivers/pci/pci.c                             | 160 +++++++++++-------
>   2 files changed, 134 insertions(+), 58 deletions(-)
>
Acked-by: Edoardo Canepa <edoardo.canepa at canonical.com>
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