Message-Id: <D7Q79WJZSFEK.R9BX1V85SV1Z@nvidia.com>
Date: Wed, 12 Feb 2025 13:59:01 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "Danilo Krummrich" <dakr@...nel.org>, <airlied@...il.com>,
 <simona@...ll.ch>, <corbet@....net>, <maarten.lankhorst@...ux.intel.com>,
 <mripard@...nel.org>, <tzimmermann@...e.de>, <ajanulgu@...hat.com>,
 <lyude@...hat.com>, <pstanner@...hat.com>, <zhiw@...dia.com>,
 <cjia@...dia.com>, <jhubbard@...dia.com>, <bskeggs@...dia.com>,
 <acurrid@...dia.com>
Cc: <ojeda@...nel.org>, <alex.gaynor@...il.com>, <boqun.feng@...il.com>,
 <gary@...yguo.net>, <bjorn3_gh@...tonmail.com>, <benno.lossin@...ton.me>,
 <a.hindborg@...nel.org>, <aliceryhl@...gle.com>, <tmgross@...ch.edu>,
 <dri-devel@...ts.freedesktop.org>, <linux-doc@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <nouveau@...ts.freedesktop.org>,
 <rust-for-linux@...r.kernel.org>, "Nouveau"
 <nouveau-bounces@...ts.freedesktop.org>
Subject: Re: [PATCH v3 1/2] gpu: nova-core: add initial driver stub

On Mon Feb 10, 2025 at 2:30 AM JST, Danilo Krummrich wrote:
> Add the initial nova-core driver stub.
>
> nova-core is intended to serve as a common base for nova-drm (the
> corresponding DRM driver) and the vGPU manager VFIO driver, serving as a
> hard- and firmware abstraction layer for GSP-based NVIDIA GPUs.
>
> The Nova project, including nova-core and nova-drm, in the long term,
> is intended to serve as the successor of Nouveau for all GSP-based GPUs.
>
> The motivation for both, starting a successor project for Nouveau and
> doing so using the Rust programming language, is documented in detail
> through a previous post on the mailing list [1], an LWN article [2] and a
> talk from LPC '24.
>
> In order to avoid the chicken and egg problem to require a user to
> upstream Rust abstractions, but at the same time require the Rust
> abstractions to implement the driver, nova-core kicks off as a driver
> stub and is subsequently developed upstream.
>
> Link: https://lore.kernel.org/dri-devel/Zfsj0_tb-0-tNrJy@cassiopeiae/T/#u [1]
> Link: https://lwn.net/Articles/990736/ [2]
> Link: https://youtu.be/3Igmx28B3BQ?si=sBdSEer4tAPKGpOs [3]
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
> ---
> Changes in v3:
>   - impl TryFrom<u32> for Chipset
>   - add Chipset::arch()
>   - initialize revision from Boot0
>   - in Firmware, eliminate repeating code pattern using a closure (thanks to
>     Alexandre)
>   - use #[expect(dead_code)] for Firmware
>
> Changes in v2:
>   - Fix module name in Kconfig description. (John)
>   - Expand Kconfig description a bit. (John)
>   - Expand name for PCI BAR0 region.
>   - Do not store / print boot0 raw register value. (John)
>   - Rename CardType to Architecture, rename enum names to represent the
>     architecture name and adjust enum values according to the register
>     definition. (John)
>   - Add an abstraction for register accesses.
>   - Print chipset, architecture and revision.
>   - Load bootloader firmware. (Timur)
> ---
>  MAINTAINERS                        |  10 ++
>  drivers/gpu/Makefile               |   1 +
>  drivers/gpu/nova-core/Kconfig      |  14 +++
>  drivers/gpu/nova-core/Makefile     |   3 +
>  drivers/gpu/nova-core/driver.rs    |  47 +++++++
>  drivers/gpu/nova-core/gpu.rs       | 189 +++++++++++++++++++++++++++++
>  drivers/gpu/nova-core/nova_core.rs |  15 +++
>  drivers/gpu/nova-core/regs.rs      |  56 +++++++++
>  drivers/video/Kconfig              |   1 +
>  9 files changed, 336 insertions(+)
>  create mode 100644 drivers/gpu/nova-core/Kconfig
>  create mode 100644 drivers/gpu/nova-core/Makefile
>  create mode 100644 drivers/gpu/nova-core/driver.rs
>  create mode 100644 drivers/gpu/nova-core/gpu.rs
>  create mode 100644 drivers/gpu/nova-core/nova_core.rs
>  create mode 100644 drivers/gpu/nova-core/regs.rs
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 25c86f47353d..5d5b7ed7da9e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7446,6 +7446,16 @@ T:	git https://gitlab.freedesktop.org/drm/nouveau.git
>  F:	drivers/gpu/drm/nouveau/
>  F:	include/uapi/drm/nouveau_drm.h
>  
> +CORE DRIVER FOR NVIDIA GPUS [RUST]
> +M:	Danilo Krummrich <dakr@...nel.org>
> +L:	nouveau@...ts.freedesktop.org
> +S:	Supported
> +Q:	https://patchwork.freedesktop.org/project/nouveau/
> +B:	https://gitlab.freedesktop.org/drm/nova/-/issues
> +C:	irc://irc.oftc.net/nouveau
> +T:	git https://gitlab.freedesktop.org/drm/nova.git nova-next
> +F:	drivers/gpu/nova-core/
> +
>  DRM DRIVER FOR OLIMEX LCD-OLINUXINO PANELS
>  M:	Stefan Mavrodiev <stefan@...mex.com>
>  S:	Maintained
> diff --git a/drivers/gpu/Makefile b/drivers/gpu/Makefile
> index 8997f0096545..36a54d456630 100644
> --- a/drivers/gpu/Makefile
> +++ b/drivers/gpu/Makefile
> @@ -5,3 +5,4 @@
>  obj-y			+= host1x/ drm/ vga/
>  obj-$(CONFIG_IMX_IPUV3_CORE)	+= ipu-v3/
>  obj-$(CONFIG_TRACE_GPU_MEM)		+= trace/
> +obj-$(CONFIG_NOVA_CORE)		+= nova-core/
> diff --git a/drivers/gpu/nova-core/Kconfig b/drivers/gpu/nova-core/Kconfig
> new file mode 100644
> index 000000000000..ad0c06756516
> --- /dev/null
> +++ b/drivers/gpu/nova-core/Kconfig
> @@ -0,0 +1,14 @@
> +config NOVA_CORE
> +	tristate "Nova Core GPU driver"
> +	depends on PCI
> +	depends on RUST
> +	depends on RUST_FW_LOADER_ABSTRACTIONS
> +	default n
> +	help
> +	  Choose this if you want to build the Nova Core driver for Nvidia
> +	  GPUs based on the GPU System Processor (GSP). This is true for Turing
> +	  and later GPUs.
> +
> +	  This driver is work in progress and may not be functional.
> +
> +	  If M is selected, the module will be called nova_core.
> diff --git a/drivers/gpu/nova-core/Makefile b/drivers/gpu/nova-core/Makefile
> new file mode 100644
> index 000000000000..2d78c50126e1
> --- /dev/null
> +++ b/drivers/gpu/nova-core/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_NOVA_CORE) += nova_core.o
> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
> new file mode 100644
> index 000000000000..63c19f140fbd
> --- /dev/null
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +use kernel::{bindings, c_str, pci, prelude::*};
> +
> +use crate::gpu::Gpu;
> +
> +#[pin_data]
> +pub(crate) struct NovaCore {
> +    #[pin]
> +    pub(crate) gpu: Gpu,
> +}
> +
> +const BAR0_SIZE: usize = 8;
> +pub(crate) type Bar0 = pci::Bar<BAR0_SIZE>;
> +
> +kernel::pci_device_table!(
> +    PCI_TABLE,
> +    MODULE_PCI_TABLE,
> +    <NovaCore as pci::Driver>::IdInfo,
> +    [(
> +        pci::DeviceId::from_id(bindings::PCI_VENDOR_ID_NVIDIA, bindings::PCI_ANY_ID as _),
> +        ()
> +    )]
> +);
> +
> +impl pci::Driver for NovaCore {
> +    type IdInfo = ();
> +    const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
> +
> +    fn probe(pdev: &mut pci::Device, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
> +        dev_dbg!(pdev.as_ref(), "Probe Nova Core GPU driver.\n");
> +
> +        pdev.enable_device_mem()?;
> +        pdev.set_master();
> +
> +        let bar = pdev.iomap_region_sized::<BAR0_SIZE>(0, c_str!("nova-core/bar0"))?;
> +
> +        let this = KBox::pin_init(
> +            try_pin_init!(Self {
> +                gpu <- Gpu::new(pdev, bar)?,
> +            }),
> +            GFP_KERNEL,
> +        )?;
> +
> +        Ok(this)
> +    }
> +}
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> new file mode 100644
> index 000000000000..e7da6a2fa29d
> --- /dev/null
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -0,0 +1,189 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +use kernel::{
> +    device, devres::Devres, error::code::*, firmware, fmt, pci, prelude::*, str::CString,
> +};
> +
> +use crate::driver::Bar0;
> +use crate::regs;
> +use core::fmt;
> +
> +/// Enum representation of the GPU chipset.
> +#[derive(fmt::Debug)]
> +pub(crate) enum Chipset {
> +    // Turing
> +    TU102 = 0x162,
> +    TU104 = 0x164,
> +    TU106 = 0x166,
> +    TU117 = 0x167,
> +    TU116 = 0x168,
> +    // Ampere
> +    GA102 = 0x172,
> +    GA103 = 0x173,
> +    GA104 = 0x174,
> +    GA106 = 0x176,
> +    GA107 = 0x177,
> +    // Ada
> +    AD102 = 0x192,
> +    AD103 = 0x193,
> +    AD104 = 0x194,
> +    AD106 = 0x196,
> +    AD107 = 0x197,
> +}
> +
> +impl Chipset {
> +    pub(crate) fn arch(&self) -> Architecture {
> +        match self {
> +            Self::TU102 | Self::TU104 | Self::TU106 | Self::TU117 | Self::TU116 => {
> +                Architecture::Turing
> +            }
> +            Self::GA102 | Self::GA103 | Self::GA104 | Self::GA106 | Self::GA107 => {
> +                Architecture::Ampere
> +            }
> +            Self::AD102 | Self::AD103 | Self::AD104 | Self::AD106 | Self::AD107 => {
> +                Architecture::Ada
> +            }
> +        }
> +    }
> +}
> +
> +// TODO
> +//
> +// The resulting strings are used to generate firmware paths, hence the
> +// generated strings have to be stable.
> +//
> +// Hence, replace with something like strum_macros derive(Display).
> +//
> +// For now, redirect to fmt::Debug for convenience.
> +impl fmt::Display for Chipset {
> +    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> +        write!(f, "{:?}", self)
> +    }
> +}
> +
> +// TODO replace with something like derive(FromPrimitive)
> +impl TryFrom<u32> for Chipset {
> +    type Error = kernel::error::Error;
> +
> +    fn try_from(value: u32) -> Result<Self, Self::Error> {
> +        match value {
> +            0x162 => Ok(Chipset::TU102),
> +            0x164 => Ok(Chipset::TU104),
> +            0x166 => Ok(Chipset::TU106),
> +            0x167 => Ok(Chipset::TU117),
> +            0x168 => Ok(Chipset::TU116),
> +            0x172 => Ok(Chipset::GA102),
> +            0x173 => Ok(Chipset::GA103),
> +            0x174 => Ok(Chipset::GA104),
> +            0x176 => Ok(Chipset::GA106),
> +            0x177 => Ok(Chipset::GA107),
> +            0x192 => Ok(Chipset::AD102),
> +            0x193 => Ok(Chipset::AD103),
> +            0x194 => Ok(Chipset::AD104),
> +            0x196 => Ok(Chipset::AD106),
> +            0x197 => Ok(Chipset::AD107),
> +            _ => Err(ENODEV),
> +        }
> +    }
> +}
> +
> +/// Enum representation of the GPU generation.
> +#[derive(fmt::Debug)]
> +pub(crate) enum Architecture {
> +    Turing,
> +    Ampere,
> +    Ada,
> +}
> +
> +pub(crate) struct Revision {
> +    major: u8,
> +    minor: u8,
> +}
> +
> +impl Revision {
> +    fn from_boot0(boot0: regs::Boot0) -> Self {
> +        Self {
> +            major: boot0.major_rev(),
> +            minor: boot0.minor_rev(),
> +        }
> +    }
> +}
> +
> +impl fmt::Display for Revision {
> +    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> +        write!(f, "{:x}.{:x}", self.major, self.minor)
> +    }
> +}
> +
> +/// Structure holding the metadata of the GPU.
> +pub(crate) struct Spec {
> +    chipset: Chipset,
> +    /// The revision of the chipset.
> +    revision: Revision,
> +}
> +
> +impl Spec {
> +    fn new(bar: &Devres<Bar0>) -> Result<Spec> {
> +        let bar = bar.try_access().ok_or(ENXIO)?;
> +        let boot0 = regs::Boot0::read(&bar);
> +
> +        Ok(Self {
> +            chipset: boot0.chipset().try_into()?,
> +            revision: Revision::from_boot0(boot0),
> +        })
> +    }
> +}
> +
> +/// Structure encapsulating the firmware blobs required for the GPU to operate.
> +#[expect(dead_code)]
> +pub(crate) struct Firmware {
> +    booter_load: firmware::Firmware,
> +    booter_unload: firmware::Firmware,
> +    bootloader: firmware::Firmware,
> +    gsp: firmware::Firmware,
> +}
> +
> +impl Firmware {
> +    fn new(dev: &device::Device, spec: &Spec, ver: &str) -> Result<Firmware> {
> +        let mut chip_name = CString::try_from_fmt(fmt!("{}", spec.chipset))?;
> +        chip_name.make_ascii_lowercase();
> +
> +        let request = |name_| {
> +            CString::try_from_fmt(fmt!("nvidia/{}/gsp/{}-{}.bin", &*chip_name, name_, ver))
> +                .and_then(|path| firmware::Firmware::request(&path, dev))
> +        };
> +
> +        Ok(Firmware {
> +            booter_load: request("booter_load")?,
> +            booter_unload: request("booter_unload")?,
> +            bootloader: request("bootloader")?,
> +            gsp: request("gsp")?,
> +        })
> +    }
> +}
> +
> +/// Structure holding the resources required to operate the GPU.
> +#[pin_data]
> +pub(crate) struct Gpu {
> +    spec: Spec,
> +    /// MMIO mapping of PCI BAR 0
> +    bar: Devres<Bar0>,
> +    fw: Firmware,
> +}
> +
> +impl Gpu {
> +    pub(crate) fn new(pdev: &pci::Device, bar: Devres<Bar0>) -> Result<impl PinInit<Self>> {
> +        let spec = Spec::new(&bar)?;
> +        let fw = Firmware::new(pdev.as_ref(), &spec, "535.113.01")?;
> +
> +        dev_info!(
> +            pdev.as_ref(),
> +            "NVIDIA (Chipset: {}, Architecture: {:?}, Revision: {})\n",
> +            spec.chipset,
> +            spec.chipset.arch(),
> +            spec.revision
> +        );
> +
> +        Ok(pin_init!(Self { spec, bar, fw }))
> +    }
> +}
> diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
> new file mode 100644
> index 000000000000..5d0230042793
> --- /dev/null
> +++ b/drivers/gpu/nova-core/nova_core.rs
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Nova Core GPU Driver
> +
> +mod driver;
> +mod gpu;
> +mod regs;
> +
> +kernel::module_pci_driver! {
> +    type: driver::NovaCore,
> +    name: "NovaCore",
> +    author: "Danilo Krummrich",
> +    description: "Nova Core GPU driver",
> +    license: "GPL v2",
> +}
> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
> new file mode 100644
> index 000000000000..f2766f95e9d1
> --- /dev/null
> +++ b/drivers/gpu/nova-core/regs.rs
> @@ -0,0 +1,56 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +use crate::driver::Bar0;
> +use kernel::revocable::RevocableGuard;
> +
> +// TODO
> +//
> +// Create register definitions via generic macros. See task "Generic register
> +// abstraction" in Documentation/gpu/nova/core/todo.rst.
> +
> +const BOOT0_OFFSET: usize = 0x00000000;
> +
> +// 3:0 - chipset minor revision
> +const BOOT0_MINOR_REV_SHIFT: u8 = 0;
> +const BOOT0_MINOR_REV_MASK: u32 = 0x0000000f;
> +
> +// 7:4 - chipset major revision
> +const BOOT0_MAJOR_REV_SHIFT: u8 = 4;
> +const BOOT0_MAJOR_REV_MASK: u32 = 0x000000f0;
> +
> +// 23:20 - chipset implementation Identifier (depends on architecture)
> +const BOOT0_IMPL_SHIFT: u8 = 20;
> +const BOOT0_IMPL_MASK: u32 = 0x00f00000;
> +
> +// 28:24 - chipset architecture identifier
> +const BOOT0_ARCH_MASK: u32 = 0x1f000000;
> +
> +// 28:20 - chipset identifier (virtual register field combining BOOT0_IMPL and
> +//         BOOT0_ARCH)
> +const BOOT0_CHIPSET_SHIFT: u8 = BOOT0_IMPL_SHIFT;
> +const BOOT0_CHIPSET_MASK: u32 = BOOT0_IMPL_MASK | BOOT0_ARCH_MASK;
> +
> +#[derive(Copy, Clone)]
> +pub(crate) struct Boot0(u32);
> +
> +impl Boot0 {
> +    #[inline]
> +    pub(crate) fn read(bar: &RevocableGuard<'_, Bar0>) -> Self {

Since RevocableGuard has a Deref implementation you can actually take a
`&Bar0` here, and let deref coercion do its thing.

Also just for confirmation: is the intent that all register offsets,
and masks are kept private within this module, with each register having
its own type and dedicated methods to read/write it and extract useful
information from it? I haven't really written Rust kernel code before,
so I was wondering how we would deal with this problem. This looks like
a pretty safe solution.

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