On Fri, Jun 02, 2023 at 11:52:13AM -0700, Alan Previn wrote:
> In the ABI header, GUC_CTB_MSG_MIN_LEN is '1' because
> GUC_CTB_HDR_LEN is 1. This aligns with H2G/G2H CTB specification
> where all command formats are defined in units of dwords so that '1'
> is a dword. Accordingly, GUC_CTB_MSG_MAX_LEN is 256-1 (i.e. 255
> dwords). However, h2g_write was incorrectly assuming that
> GUC_CTB_MSG_MAX_LEN was in bytes. Fix this.
>
The patch itself make sense but concerned about the value of
GUC_CTB_MSG_MAX_LEN. Is the max size of CTB really 256 DWs? That seems
way to large. Also I think some tools are going to complain with the
stack being this large too.
Matt
> Signed-off-by: Alan Previn <alan.previn.teres.alexis@xxxxxxxxx>
> ---
> drivers/gpu/drm/xe/xe_guc_ct.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> index 137c184df487..8e9df6052b02 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -401,7 +401,7 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> {
> struct xe_device *xe = ct_to_xe(ct);
> struct guc_ctb *h2g = &ct->ctbs.h2g;
> - u32 cmd[GUC_CTB_MSG_MAX_LEN / sizeof(u32)];
> + u32 cmd[GUC_CTB_MSG_MAX_LEN];
> u32 cmd_len = len + GUC_CTB_HDR_LEN;
> u32 cmd_idx = 0, i;
> u32 tail = h2g->info.tail;
> @@ -409,7 +409,7 @@ static int h2g_write(struct xe_guc_ct *ct, const u32 *action, u32 len,
> tail * sizeof(u32));
>
> lockdep_assert_held(&ct->lock);
> - XE_BUG_ON(len * sizeof(u32) > GUC_CTB_MSG_MAX_LEN);
> + XE_BUG_ON(len > GUC_CTB_MSG_MAX_LEN - 1);
> XE_BUG_ON(tail > h2g->info.size);
>
> /* Command will wrap, zero fill (NOPs), return and check credits again */
>
> base-commit: 9f49c413b187c00f223eaf1e8dbe2c1a97c9954b
> --
> 2.39.0
>
