github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-07 06:17:02 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

accel/amdxdna: document trusted mailbox ring geometry and drop the power-of-two check

Browse Source 
The mailbox ring buffer geometry comes from AMD signed firmware, through
the management or mailbox information block, or through the CREATE_CONTEXT
response, and the driver trusts it by design.

The power-of-two test on rb_size was a firmware debugging aid. Nothing in
the driver derives a mask, a shift or a modulo from rb_size, so no code
depends on the property it tested. The ring index wrap is handled by the
explicit comparisons in mailbox_send_msg() and mailbox_get_msg().

Replace the test with a comment that records the design, so that
automated review does not flag the absence of a bound here again.

Suggested-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://lore.kernel.org/all/67698952-6394-44a8-01fe-3e3558b7cb4c@amd.com/
Signed-off-by: Eva Crystal <0xiviel@gmail.com>
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20261002205814.178031-1-0xiviel@gmail.com
This commit is contained in:
Eva Crystal 2026-10-03 09:58:14 +13:00 committed by Lizhi Hou
parent 3d65a38375
commit 5d7b464a4f
1 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/accel/amdxdna/amdxdna_mailbox.c
View File

@ -569,11 +569,13 @@ xdna_mailbox_start_channel(struct mailbox_channel *mb_chann,
{
int ret;
if (!is_power_of_2(x2i->rb_size) || !is_power_of_2(i2x->rb_size)) {
pr_err("Ring buf size must be power of 2\n");
return -EINVAL;
}
/*
* The ring buffer geometry, rb_start_addr and rb_size for both the
* x2i and the i2x channel, comes from AMD signed firmware, through
* the management or mailbox information block, or through the
* CREATE_CONTEXT response. The driver trusts those values by design
* and does not bound them against the mapped region.
*/
mb_chann->msix_irq = mb_irq;
mb_chann->iohub_int_addr = iohub_int_addr;
memcpy(&mb_chann->res[CHAN_RES_X2I], x2i, sizeof(*x2i));