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Subject[PATCH] habanalabs: prevent CPU soft lockup on Palladium
Date
Unmapping ptes in the device MMU on Palladium can take a long time, which
can cause a kernel BUG of CPU soft lockup.

This patch minimize the chances for this bug by sleeping a little between
unmapping ptes.

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
---
drivers/misc/habanalabs/memory.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/habanalabs/memory.c b/drivers/misc/habanalabs/memory.c
index 39788b1cf8d0..e9e163545584 100644
--- a/drivers/misc/habanalabs/memory.c
+++ b/drivers/misc/habanalabs/memory.c
@@ -1046,10 +1046,17 @@ static int unmap_device_va(struct hl_ctx *ctx, u64 vaddr)

mutex_lock(&ctx->mmu_lock);

- for (i = 0 ; i < phys_pg_pack->npages ; i++, next_vaddr += page_size)
+ for (i = 0 ; i < phys_pg_pack->npages ; i++, next_vaddr += page_size) {
if (hl_mmu_unmap(ctx, next_vaddr, page_size))
dev_warn_ratelimited(hdev->dev,
- "unmap failed for vaddr: 0x%llx\n", next_vaddr);
+ "unmap failed for vaddr: 0x%llx\n", next_vaddr);
+
+ /* unmapping on Palladium can be really long, so avoid a CPU
+ * soft lockup bug by sleeping a little between unmapping pages
+ */
+ if (hdev->pldm)
+ usleep_range(500, 1000);
+ }

hdev->asic_funcs->mmu_invalidate_cache(hdev, true);

--
2.17.1
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