[PATCH 5/9] drm/tyr: add user and MCU VM specifications

[Ke Sun via B4 Relay]

From: Alvin Sun <alvin.sun@xxxxxxxxx>

Distinguish MCU VMs from user VMs, and compute the user/kernel
GPU VA split for user VMs.

Signed-off-by: Alvin Sun <alvin.sun@xxxxxxxxx>
---
 drivers/gpu/drm/tyr/fw.rs |   8 +--
 drivers/gpu/drm/tyr/vm.rs | 134 +++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 131 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/tyr/fw.rs b/drivers/gpu/drm/tyr/fw.rs
index 47d25c901bd01..9b4b488521b85 100644
--- a/drivers/gpu/drm/tyr/fw.rs
+++ b/drivers/gpu/drm/tyr/fw.rs
@@ -51,7 +51,6 @@
         KernelBoVaAlloc, //
     },
     gpu::GpuInfo,
-
     mmu::Mmu,
     regs::{
         gpu_control::{
@@ -66,7 +65,10 @@
             JOB_IRQ_RAWSTAT, //
         }, //
     },
-    vm::Vm, //
+    vm::{
+        Vm,
+        VmSpec, //
+    }, //
 };
 
 mod parser;
@@ -220,7 +222,7 @@ pub(crate) fn new(
         mmu: ArcBorrow<'_, Mmu<'drm>>,
         gpu_info: &GpuInfo,
     ) -> Result<Firmware<'drm>> {
-        let vm = Vm::new(dev, ddev, mmu, gpu_info)?;
+        let vm = Vm::new(dev, ddev, mmu, gpu_info, VmSpec::Mcu)?;
         vm.activate()?;
 
         let result = (|| {
diff --git a/drivers/gpu/drm/tyr/vm.rs b/drivers/gpu/drm/tyr/vm.rs
index c5e307b1e2416..76c3d60bb2fe2 100644
--- a/drivers/gpu/drm/tyr/vm.rs
+++ b/drivers/gpu/drm/tyr/vm.rs
@@ -8,6 +8,7 @@
 //! mapped into hardware address space (AS) slots for GPU execution.
 
 use core::marker::PhantomData;
+use core::num::NonZeroU64;
 use core::ops::Range;
 
 use kernel::{
@@ -43,6 +44,8 @@
     new_mutex,
     prelude::*,
     sizes::{
+        LargeSizeConstants,
+        SizeConstants,
         SZ_1G,
         SZ_2M,
         SZ_4K, //
@@ -154,6 +157,109 @@ fn try_from(value: u32) -> Result<Self, Self::Error> {
     }
 }
 
+/// User VA size request for a user VM.
+pub(crate) enum UserVaRequest {
+    /// Split based on `task_size()` and the GPU VA range.
+    Auto,
+    /// Caller-specified size; construction guarantees `> 0`.
+    Fixed(NonZeroU64),
+}
+
+impl UserVaRequest {
+    /// UAPI boundary normalization: `0` -> [`Auto`](Self::Auto).
+    pub(crate) fn from_uapi(v: u64) -> Self {
+        match NonZeroU64::new(v) {
+            Some(size) => Self::Fixed(size),
+            None => Self::Auto,
+        }
+    }
+}
+
+pub(crate) enum VmSpec {
+    /// MCU/firmware VM, entirely kernel-managed.
+    Mcu,
+    /// User VM: full GPU VA range, split into user/kernel per `user_va`.
+    User { user_va: UserVaRequest },
+}
+
+/// Final user/kernel VA layout for a VM.
+pub(crate) struct VmLayout {
+    /// Full GPU VA range covered by this VM.
+    pub(crate) full: Range<u64>,
+    /// User-accessible VA range. Empty for MCU VMs.
+    pub(crate) user: Range<u64>,
+}
+
+impl VmLayout {
+    /// Kernel VA range, reserved for future kernel object allocation.
+    #[expect(dead_code)]
+    pub(crate) fn kernel(&self) -> Range<u64> {
+        self.user.end..self.full.end
+    }
+
+    /// Compute a user/kernel split for a user VM from the full GPU VA range and
+    /// a user request.
+    pub(crate) fn compute(full: Range<u64>, req: UserVaRequest) -> Result<Self> {
+        /// Minimum VA space reserved for kernel objects (heaps, ring buffers, ...).
+        const MIN_KERNEL_VA: u64 = u64::SZ_256M;
+
+        if full.end <= MIN_KERNEL_VA {
+            pr_err!(
+                "Invalid VA range {:#x}..{:#x}, kernel VA min required: >{:#x}\n",
+                full.start,
+                full.end,
+                MIN_KERNEL_VA
+            );
+            return Err(EINVAL);
+        }
+
+        let user_max = full.end - MIN_KERNEL_VA;
+
+        let user_end = match req {
+            UserVaRequest::Fixed(v) => {
+                let user_size = v.get();
+                if user_size > user_max {
+                    pr_err!(
+                        "Requested user VA range {:#x} exceeds maximum {:#x}\n",
+                        user_size,
+                        user_max
+                    );
+                    return Err(EINVAL);
+                }
+                user_size
+            }
+            UserVaRequest::Auto => {
+                let task_size = current!().mm().map(|mm| mm.task_size());
+                let candidate = match task_size {
+                    // `task_size()` returns usize; widen to u64 for the comparison.
+                    Some(t) if (t as u64) < full.end => t as u64,
+                    None | Some(_) => {
+                        // If the range exceeds 4G, split it in two so CPU and
+                        // GPU share the same addresses (SVM).
+                        if full.end > u64::SZ_4G {
+                            full.end / 2
+                        } else {
+                            user_max
+                        }
+                    }
+                };
+                candidate.min(user_max)
+            }
+        };
+
+        let delta = full.end - user_end;
+        // Pick a kernel VA range that's a power of two, to have a clear split.
+        let kernel_va_range = 1u64 << delta.ilog2();
+        let kernel_va_start = full.end - kernel_va_range;
+        let full_start = full.start;
+
+        Ok(Self {
+            full,
+            user: full_start..kernel_va_start,
+        })
+    }
+}
+
 /// Arguments for a virtual memory map operation.
 struct VmMapArgs<'drm> {
     /// Access permissions and caching behavior for the mapping.
@@ -329,8 +435,8 @@ pub(crate) struct Vm<'drm> {
     /// Non-core part of the GPUVM. Can be used for stuff that doesn't modify the
     /// internal mapping tree, like GpuVm::obtain()
     gpuvm: ARef<GpuVm<GpuVmData<'drm>>>,
-    /// VA range for this VM.
-    va_range: Range<u64>,
+    /// VA layout for this VM.
+    pub(crate) layout: VmLayout,
 }
 
 impl<'drm> Vm<'drm> {
@@ -343,6 +449,7 @@ pub(crate) fn new(
         ddev: &TyrDrmDevice,
         mmu: ArcBorrow<'_, Mmu<'drm>>,
         gpu_info: &GpuInfo,
+        spec: VmSpec,
     ) -> Result<Arc<Vm<'drm>>> {
         let mmu_features = MMU_FEATURES::from_raw(gpu_info.mmu_features);
         let va_bits = mmu_features.va_bits().get();
@@ -351,6 +458,14 @@ pub(crate) fn new(
         let range = 0..(1u64 << va_bits);
         let reserve_range = 0..0u64;
 
+        let layout = match spec {
+            VmSpec::Mcu => VmLayout {
+                full: range.clone(),
+                user: 0..0u64,
+            },
+            VmSpec::User { user_va } => VmLayout::compute(range.clone(), user_va)?,
+        };
+
         // dummy_obj is used to initialize the GPUVM tree.
         let dummy_obj = gem::new_dummy_object(ddev).inspect_err(|e| {
             dev_err!(dev, "Failed to create dummy GEM object: {:?}", e);
@@ -380,7 +495,7 @@ pub(crate) fn new(
                 mmu: mmu.into(),
                 gpuvm,
                 gpuvm_unique <- new_mutex!(gpuvm_unique),
-                va_range: range,
+                layout,
             }),
             GFP_KERNEL,
         )?;
@@ -414,7 +529,10 @@ pub(crate) fn kill(&self) {
         // TODO: Turn the VM into a state where it can't be used.
         let _ = self.deactivate();
         let _ = self
-            .unmap_range(self.va_range.start, self.va_range.end - self.va_range.start)
+            .unmap_range(
+                self.layout.full.start,
+                self.layout.full.end - self.layout.full.start,
+            )
             .inspect_err(|e| {
                 dev_err!(self.dev, "Failed to unmap range during deactivate: {:?}", e);
             });
@@ -551,14 +669,14 @@ pub(crate) fn unmap_range(&self, va: u64, size: u64) -> Result {
 
         let end = va.checked_add(size).ok_or(EINVAL)?;
 
-        if va < self.va_range.start || end > self.va_range.end {
+        if va < self.layout.full.start || end > self.layout.full.end {
             dev_err!(
                 self.dev,
                 "Unmap range {:#x}..{:#x} exceeds VM range {:#x}..{:#x}",
                 va,
                 end,
-                self.va_range.start,
-                self.va_range.end
+                self.layout.full.start,
+                self.layout.full.end
             );
             return Err(EINVAL);
         }
@@ -568,7 +686,7 @@ pub(crate) fn unmap_range(&self, va: u64, size: u64) -> Result {
             region: va..end,
         };
 
-        let full_vm = va == self.va_range.start && end == self.va_range.end;
+        let full_vm = va == self.layout.full.start && end == self.layout.full.end;
 
         let mut resources = VmOpResources {
             preallocated_gpuvas: if full_vm {

-- 
2.43.0