From: Tim Kovalenko <[email protected]> The `Cmdq::new` function was allocating a `PteArray` struct on the stack and was causing a stack overflow with 8216 bytes.
Modify the `PteArray` to calculate and write the Page Table Entries directly into the coherent DMA buffer one-by-one. This reduces the stack usage quite a lot. Signed-off-by: Tim Kovalenko <[email protected]> --- drivers/gpu/nova-core/gsp.rs | 34 +++++++++++++++++++--------------- drivers/gpu/nova-core/gsp/cmdq.rs | 15 ++++++++++++++- 2 files changed, 33 insertions(+), 16 deletions(-) diff --git a/drivers/gpu/nova-core/gsp.rs b/drivers/gpu/nova-core/gsp.rs index 25cd48514c777cb405a2af0acf57196b2e2e7837..20170e483e04c476efce8997b3916b0ad829ed38 100644 --- a/drivers/gpu/nova-core/gsp.rs +++ b/drivers/gpu/nova-core/gsp.rs @@ -47,16 +47,11 @@ 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)) + /// Returns the page table entry for `index`, for a mapping starting at `start` DmaAddress. + fn entry(start: DmaAddress, index: usize) -> Result<u64> { + start + .checked_add(num::usize_as_u64(index) << GSP_PAGE_SHIFT) + .ok_or(EOVERFLOW) } } @@ -86,16 +81,25 @@ fn new(dev: &device::Device<device::Bound>) -> Result<Self> { NUM_PAGES * GSP_PAGE_SIZE, GFP_KERNEL | __GFP_ZERO, )?); - let ptes = PteArray::<NUM_PAGES>::new(obj.0.dma_handle())?; + + let start_addr = 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. + let pte_region = unsafe { obj.0 - .as_slice_mut(size_of::<u64>(), size_of_val(&ptes))? - .copy_from_slice(ptes.as_bytes()) + .as_slice_mut(size_of::<u64>(), NUM_PAGES * size_of::<u64>())? }; + // This is a one by one GSP Page write to the memory + // to avoid stack overflow when allocating the whole array at once. + for (i, chunk) in pte_region.chunks_exact_mut(size_of::<u64>()).enumerate() { + let pte_value = start_addr + .checked_add(num::usize_as_u64(i) << GSP_PAGE_SHIFT) + .ok_or(EOVERFLOW)?; + + chunk.copy_from_slice(&pte_value.to_ne_bytes()); + } + Ok(obj) } } diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs index 0056bfbf0a44cfbc5a0ca08d069f881b877e1edc..c8327d3098f73f9b880eee99038ad10a16e1e32d 100644 --- a/drivers/gpu/nova-core/gsp/cmdq.rs +++ b/drivers/gpu/nova-core/gsp/cmdq.rs @@ -202,7 +202,20 @@ fn new(dev: &device::Device<device::Bound>) -> Result<Self> { let gsp_mem = CoherentAllocation::<GspMem>::alloc_coherent(dev, 1, GFP_KERNEL | __GFP_ZERO)?; - dma_write!(gsp_mem, [0]?.ptes, PteArray::new(gsp_mem.dma_handle())?); + + const NUM_PTES: usize = GSP_PAGE_SIZE / size_of::<u64>(); + + let start = gsp_mem.dma_handle(); + // One by one GSP Page write to the memory to avoid stack overflow when allocating + // the whole array at once. + for i in 0..NUM_PTES { + dma_write!( + gsp_mem, + [0]?.ptes.0[i], + PteArray::<NUM_PTES>::entry(start, i)? + ); + } + dma_write!( gsp_mem, [0]?.cpuq.tx, -- 2.53.0
