linux-kernel - [PATCH RFC v6 26/26] nova-core: mm: Add BarUser to struct Gpu and create at boot

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Message-Id: <20260120204303.3229303-27-joelagnelf@nvidia.com>
Date: Tue, 20 Jan 2026 15:43:03 -0500
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
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	Joel Fernandes <joelagnelf@...dia.com>
Subject: [PATCH RFC v6 26/26] nova-core: mm: Add BarUser to struct Gpu and create at boot

Add a BarUser field to struct Gpu and eagerly create it during GPU
initialization. The BarUser provides the BAR1 user interface for CPU
access to GPU virtual memory through the GPU's MMU.

The BarUser is initialized using BAR1 PDE base address from GSP static
info, MMU version and BAR1 size obtained from platform device.

Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
---
 drivers/gpu/nova-core/gpu.rs | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index dd05ad23f763..15d8d42ecfa8 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -26,7 +26,12 @@
         commands::GetGspStaticInfoReply,
         Gsp, //
     },
-    mm::GpuMm,
+    mm::{
+        bar_user::BarUser,
+        pagetable::MmuVersion,
+        GpuMm,
+        VramAddress, //
+    },
     regs,
 };
 
@@ -35,6 +40,7 @@
 struct BootParams {
     usable_vram_start: u64,
     usable_vram_size: u64,
+    bar1_pde_base: u64,
 }
 
 macro_rules! define_chipset {
@@ -271,6 +277,8 @@ pub(crate) struct Gpu {
     gsp: Gsp,
     /// Static GPU information from GSP.
     gsp_static_info: GetGspStaticInfoReply,
+    /// BAR1 user interface for CPU access to GPU virtual memory.
+    bar_user: BarUser,
 }
 
 impl Gpu {
@@ -284,6 +292,7 @@ pub(crate) fn new<'a>(
         let boot_params: Cell<BootParams> = Cell::new(BootParams {
             usable_vram_start: 0,
             usable_vram_size: 0,
+            bar1_pde_base: 0,
         });
 
         try_pin_init!(Self {
@@ -328,6 +337,7 @@ pub(crate) fn new<'a>(
                 boot_params.set(BootParams {
                     usable_vram_start: usable_vram.start,
                     usable_vram_size: usable_vram.end - usable_vram.start,
+                    bar1_pde_base: info.bar1_pde_base(),
                 });
 
                 info
@@ -344,6 +354,16 @@ pub(crate) fn new<'a>(
                 })?
             },
 
+            // Create BAR1 user interface for CPU access to GPU virtual memory.
+            // Uses the BAR1 PDE base from GSP and full BAR1 size for VA space.
+            bar_user: {
+                let params = boot_params.get();
+                let pdb_addr = VramAddress::new(params.bar1_pde_base);
+                let mmu_version = MmuVersion::from(spec.chipset.arch());
+                let bar1_size = pdev.resource_len(1)?;
+                BarUser::new(pdb_addr, mmu_version, bar1_size)?
+            },
+
             bar: devres_bar,
         })
     }
-- 
2.34.1