[PATCH v8 04/16] gpu: nova-core: Create initial Gsp

Alexandre Courbot
2025-11-07T23:43:05Z

From: Alistair Popple <apopple at nvidia.com>

The GSP requires several areas of memory to operate. Each of these have
their own simple embedded page tables. Set these up and map them for DMA
to/from GSP using CoherentAllocation's. Return the DMA handle describing
where each of these regions are for future use when booting GSP.

Co-developed-by: Alexandre Courbot <acourbot at nvidia.com>
Signed-off-by: Alexandre Courbot <acourbot at nvidia.com>
Signed-off-by: Alistair Popple <apopple at nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs                      |   2 +-
 drivers/gpu/nova-core/gsp.rs                      | 122 ++++++++++++++++++++--
 drivers/gpu/nova-core/gsp/fw.rs                   |  60 +++++++++++
 drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs |  19 ++++
 4 files changed, 194 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 802e71e4f97d..03dae437bc37 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -231,7 +231,7 @@ pub(crate) fn new<'a>(

             sec2_falcon: Falcon::new(pdev.as_ref(), spec.chipset)?,

-            gsp <- Gsp::new(),
+            gsp <- Gsp::new(pdev)?,

             _: { gsp.boot(pdev, bar, spec.chipset, gsp_falcon, sec2_falcon)? },

diff --git a/drivers/gpu/nova-core/gsp.rs b/drivers/gpu/nova-core/gsp.rs
index aa2a9e6654e4..ea6a1f053780 100644
--- a/drivers/gpu/nova-core/gsp.rs
+++ b/drivers/gpu/nova-core/gsp.rs
@@ -2,23 +2,129 @@

 mod boot;

+use kernel::device;
+use kernel::dma::CoherentAllocation;
+use kernel::dma::DmaAddress;
+use kernel::dma_write;
+use kernel::pci;
 use kernel::prelude::*;
+use kernel::transmute::AsBytes;

 mod fw;

+use fw::LibosMemoryRegionInitArgument;
+
 pub(crate) use fw::{GspFwWprMeta, LibosParams};

+use crate::num;
+
 pub(crate) const GSP_PAGE_SHIFT: usize = 12;
 pub(crate) const GSP_PAGE_SIZE: usize = 1 << GSP_PAGE_SHIFT;

-/// GSP runtime data.
-///
-/// This is an empty pinned placeholder for now.
-#[pin_data]
-pub(crate) struct Gsp {}
+/// Number of GSP pages to use in a RM log buffer.
+const RM_LOG_BUFFER_NUM_PAGES: usize = 0x10;

-impl Gsp {
-    pub(crate) fn new() -> impl PinInit<Self> {
-        pin_init!(Self {})
+/// Array of page table entries, as understood by the GSP bootloader.
+#[repr(C)]
+struct PteArray<const NUM_ENTRIES: usize>([u64; NUM_ENTRIES]);
+
+/// SAFETY: arrays of `u64` implement `AsBytes` and we are but a wrapper around
one.
+unsafe impl<const NUM_ENTRIES: usize> AsBytes for
PteArray<NUM_ENTRIES> {}
+
+impl<const NUM_PAGES: usize> PteArray<NUM_PAGES> {
+    /// Creates a new page table array mapping `NUM_PAGES` GSP pages starting
at address `start`.
+    fn new(start: DmaAddress) -> Result<Self> {
+        let mut ptes = [0u64; NUM_PAGES];
+        for (i, pte) in ptes.iter_mut().enumerate() {
+            *pte = start
+                .checked_add(num::usize_as_u64(i) << GSP_PAGE_SHIFT)
+                .ok_or(EOVERFLOW)?;
+        }
+
+        Ok(Self(ptes))
+    }
+}
+
+/// The logging buffers are byte queues that contain encoded printf-like
+/// messages from GSP-RM.  They need to be decoded by a special application
+/// that can parse the buffers.
+///
+/// The 'loginit' buffer contains logs from early GSP-RM init and
+/// exception dumps.  The 'logrm' buffer contains the subsequent logs.
Both are
+/// written to directly by GSP-RM and can be any multiple of GSP_PAGE_SIZE.
+///
+/// The physical address map for the log buffer is stored in the buffer
+/// itself, starting with offset 1. Offset 0 contains the "put"
pointer (pp).
+/// Initially, pp is equal to 0. If the buffer has valid logging data in it,
+/// then pp points to index into the buffer where the next logging entry will
+/// be written. Therefore, the logging data is valid if:
+///   1 <= pp < sizeof(buffer)/sizeof(u64)
+struct LogBuffer(CoherentAllocation<u8>);
+
+impl LogBuffer {
+    /// Creates a new `LogBuffer` mapped on `dev`.
+    fn new(dev: &device::Device<device::Bound>) ->
Result<Self> {
+        const NUM_PAGES: usize = RM_LOG_BUFFER_NUM_PAGES;
+
+        let mut obj = Self(CoherentAllocation::<u8>::alloc_coherent(
+            dev,
+            NUM_PAGES * GSP_PAGE_SIZE,
+            GFP_KERNEL | __GFP_ZERO,
+        )?);
+        let ptes = PteArray::<NUM_PAGES>::new(obj.0.dma_handle())?;
+
+        // SAFETY: `obj` has just been created and we are its sole user.
+        unsafe {
+            // Copy the self-mapping PTE at the expected location.
+            obj.0
+                .as_slice_mut(size_of::<u64>(), size_of_val(&ptes))?
+                .copy_from_slice(ptes.as_bytes())
+        };
+
+        Ok(obj)
+    }
+}
+
+/// GSP runtime data.
+#[pin_data]
+pub(crate) struct Gsp {
+    /// Libos arguments.
+    pub(crate) libos: CoherentAllocation<LibosMemoryRegionInitArgument>,
+    /// Init log buffer.
+    loginit: LogBuffer,
+    /// Interrupts log buffer.
+    logintr: LogBuffer,
+    /// RM log buffer.
+    logrm: LogBuffer,
+}
+
+impl Gsp {
+    // Creates an in-place initializer for a `Gsp` manager for `pdev`.
+    pub(crate) fn new(pdev: &pci::Device<device::Bound>) ->
Result<impl PinInit<Self, Error>> {
+        let dev = pdev.as_ref();
+        let libos =
CoherentAllocation::<LibosMemoryRegionInitArgument>::alloc_coherent(
+            dev,
+            GSP_PAGE_SIZE / size_of::<LibosMemoryRegionInitArgument>(),
+            GFP_KERNEL | __GFP_ZERO,
+        )?;
+
+        // Initialise the logging structures. The OpenRM equivalents are in:
+        // _kgspInitLibosLoggingStructures (allocates memory for buffers)
+        // kgspSetupLibosInitArgs_IMPL (creates pLibosInitArgs[] array)
+        let loginit = LogBuffer::new(dev)?;
+        dma_write!(libos[0] =
LibosMemoryRegionInitArgument::new("LOGINIT", &loginit.0))?;
+
+        let logintr = LogBuffer::new(dev)?;
+        dma_write!(libos[1] =
LibosMemoryRegionInitArgument::new("LOGINTR", &logintr.0))?;
+
+        let logrm = LogBuffer::new(dev)?;
+        dma_write!(libos[2] =
LibosMemoryRegionInitArgument::new("LOGRM", &logrm.0))?;
+
+        Ok(try_pin_init!(Self {
+            libos,
+            loginit,
+            logintr,
+            logrm,
+        }))
     }
 }
diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 436c00d07b16..458b5610061f 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -8,11 +8,16 @@
 use core::ops::Range;

 use kernel::{
+    dma::CoherentAllocation,
     ptr::{
         Alignable,
         Alignment, //
     },
     sizes::SZ_1M,
+    transmute::{
+        AsBytes,
+        FromBytes, //
+    },
 };

 use crate::{
@@ -116,3 +121,58 @@ pub(crate) fn wpr_heap_size(&self, chipset: Chipset,
fb_size: u64) -> u64 {
 /// addresses of the GSP bootloader and firmware.
 #[repr(transparent)]
 pub(crate) struct GspFwWprMeta(bindings::GspFwWprMeta);
+
+/// Struct containing the arguments required to pass a memory buffer to the GSP
+/// for use during initialisation.
+///
+/// The GSP only understands 4K pages (GSP_PAGE_SIZE), so even if the kernel is
+/// configured for a larger page size (e.g. 64K pages), we need to give
+/// the GSP an array of 4K pages. Since we only create physically contiguous
+/// buffers the math to calculate the addresses is simple.
+///
+/// The buffers must be a multiple of GSP_PAGE_SIZE.  GSP-RM also currently
+/// ignores the @kind field for LOGINIT, LOGINTR, and LOGRM, but expects the
+/// buffers to be physically contiguous anyway.
+///
+/// The memory allocated for the arguments must remain until the GSP sends the
+/// init_done RPC.
+#[repr(transparent)]
+pub(crate) struct
LibosMemoryRegionInitArgument(bindings::LibosMemoryRegionInitArgument);
+
+// SAFETY: Padding is explicit and does not contain uninitialized data.
+unsafe impl AsBytes for LibosMemoryRegionInitArgument {}
+
+// SAFETY: This struct only contains integer types for which all bit patterns
+// are valid.
+unsafe impl FromBytes for LibosMemoryRegionInitArgument {}
+
+impl LibosMemoryRegionInitArgument {
+    pub(crate) fn new<A: AsBytes + FromBytes>(
+        name: &'static str,
+ obj: &CoherentAllocation,
+    ) -> Self {
+        /// Generates the `ID8` identifier required for some GSP objects.
+        fn id8(name: &str) -> u64 {
+            let mut bytes = [0u8; core::mem::size_of::<u64>()];
+
+            for (c, b) in name.bytes().rev().zip(&mut bytes) {
+                *b = c;
+            }
+
+            u64::from_ne_bytes(bytes)
+        }
+
+        Self(bindings::LibosMemoryRegionInitArgument {
+            id8: id8(name),
+            pa: obj.dma_handle(),
+            size: num::usize_as_u64(obj.size()),
+            kind: num::u32_into_u8::<
+                {
bindings::LibosMemoryRegionKind_LIBOS_MEMORY_REGION_CONTIGUOUS },
+            >(),
+            loc: num::u32_into_u8::<
+                { bindings::LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_SYSMEM
},
+            >(),
+            ..Default::default()
+        })
+    }
+}
diff --git a/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
b/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
index 0407000cca22..6a14cc324391 100644
--- a/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
+++ b/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
@@ -124,3 +124,22 @@ fn default() -> Self {
         }
     }
 }
+pub type LibosAddress = u64_;
+pub const LibosMemoryRegionKind_LIBOS_MEMORY_REGION_NONE: LibosMemoryRegionKind
= 0;
+pub const LibosMemoryRegionKind_LIBOS_MEMORY_REGION_CONTIGUOUS:
LibosMemoryRegionKind = 1;
+pub const LibosMemoryRegionKind_LIBOS_MEMORY_REGION_RADIX3:
LibosMemoryRegionKind = 2;
+pub type LibosMemoryRegionKind = ffi::c_uint;
+pub const LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_NONE:
LibosMemoryRegionLoc = 0;
+pub const LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_SYSMEM:
LibosMemoryRegionLoc = 1;
+pub const LibosMemoryRegionLoc_LIBOS_MEMORY_REGION_LOC_FB: LibosMemoryRegionLoc
= 2;
+pub type LibosMemoryRegionLoc = ffi::c_uint;
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct LibosMemoryRegionInitArgument {
+    pub id8: LibosAddress,
+    pub pa: LibosAddress,
+    pub size: LibosAddress,
+    pub kind: u8_,
+    pub loc: u8_,
+    pub __bindgen_padding_0: [u8; 6usize],
+}

--
2.51.2