The current code indexes into `after_rx` using `tx` which is an index
for the whole buffer, not the split buffer `after_rx`.
Also add more rigorous no-panic proofs.
Fixes: 75f6b1de8133 ("gpu: nova-core: gsp: Add GSP command queue bindings and
handling")
Signed-off-by: Eliot Courtney <[email protected]>
---
drivers/gpu/nova-core/gsp/cmdq.rs | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs
b/drivers/gpu/nova-core/gsp/cmdq.rs
index 333bf0125d74..16895f5281b7 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -1,7 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
use core::{
- cmp,
mem,
sync::atomic::{
fence,
@@ -265,13 +264,19 @@ fn new(dev: &device::Device<device::Bound>) ->
Result<Self> {
// - We will only access the driver-owned part of the shared memory.
// - Per the safety statement of the function, no concurrent access
will be performed.
let gsp_mem = &unsafe { self.0.as_slice(0, 1) }.unwrap()[0];
- // PANIC: per the invariant of `cpu_read_ptr`, `rx` is `<
MSGQ_NUM_PAGES`.
- let (before_rx, after_rx) = gsp_mem.gspq.msgq.data.split_at(rx);
-
- match tx.cmp(&rx) {
- cmp::Ordering::Equal => (&[], &[]),
- cmp::Ordering::Greater => (&after_rx[..tx], &[]),
- cmp::Ordering::Less => (after_rx, &before_rx[..tx]),
+ let data = &gsp_mem.gspq.msgq.data;
+
+ // The area starting at `rx` and ending at `tx - 1` modulo
MSGQ_NUM_PAGES, inclusive,
+ // belongs to the driver for reading.
+ // PANIC:
+ // - per the invariant of `cpu_read_ptr`, `rx < MSGQ_NUM_PAGES`
+ // - per the invariant of `gsp_write_ptr`, `tx < MSGQ_NUM_PAGES`
+ if rx <= tx {
+ // The area is contiguous.
+ (&data[rx..tx], &[])
+ } else {
+ // The area is discontiguous.
+ (&data[rx..], &data[..tx])
}
}
--
2.52.0
