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| author | David Francis <David.Francis@amd.com> | 2026-08-05 09:51:35 -0400 |
|---|---|---|
| committer | Alex Deucher <alexander.deucher@amd.com> | 2026-09-17 11:56:02 -0400 |
| commit | c883d0a132d430ef7ebb23fd94323be94d0fbdb8 (patch) | |
| tree | b434f8ad8e3951dbc5cf9bd088367a74983657b4 | |
| parent | 04de4007d32385b8b6a5dd72bff3146dfdc592c3 (diff) | |
| download | linux-next-c883d0a132d430ef7ebb23fd94323be94d0fbdb8.tar.gz linux-next-c883d0a132d430ef7ebb23fd94323be94d0fbdb8.zip | |
drm/amdkfd: Avoid integer underflow with ffs in EOP ring size calc
The low 6 bits of cp_hqd_eop_control store the base-2 logarithm
of the EOP ring size. This was calculated as
ffs(q->eop_ring_buffer_size / sizeof(unsigned int)) - 1 - 1
But ffs can in theory return 1 or 0, so this could underflow
(although in practice the ring buffer size cannot be less than 4096).
Change this to
ffs(q->eop_ring_buffer_size / sizeof(unsigned int) / 4)
using properties of logarithms.
Reviewed-by: Kent Russell <kent.russell@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 4f18c56630383c14bfc6b2d65f88f2f895d2121a)
Cc: stable@vger.kernel.org
4 files changed, 4 insertions, 4 deletions
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v10.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v10.c index e034da638c07..4f8a8a1a6186 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v10.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v10.c @@ -204,7 +204,7 @@ static void update_mqd(struct mqd_manager *mm, void *mqd, * is safe, giving a maximum field value of 0xA. */ m->cp_hqd_eop_control = q->eop_ring_buffer_size ? min(0xA, - ffs(q->eop_ring_buffer_size / sizeof(unsigned int)) - 1 - 1) : 0; + ffs(q->eop_ring_buffer_size / sizeof(unsigned int) / 4)) : 0; m->cp_hqd_eop_base_addr_lo = lower_32_bits(q->eop_ring_buffer_address >> 8); m->cp_hqd_eop_base_addr_hi = diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v11.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v11.c index 350fcbbba4b2..bf015dc5b868 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v11.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v11.c @@ -242,7 +242,7 @@ static void update_mqd(struct mqd_manager *mm, void *mqd, * is safe, giving a maximum field value of 0xA. */ m->cp_hqd_eop_control = q->eop_ring_buffer_size ? min(0xA, - ffs(q->eop_ring_buffer_size / sizeof(unsigned int)) - 1 - 1) : 0; + ffs(q->eop_ring_buffer_size / sizeof(unsigned int) / 4)) : 0; m->cp_hqd_eop_base_addr_lo = lower_32_bits(q->eop_ring_buffer_address >> 8); m->cp_hqd_eop_base_addr_hi = diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12.c index 63f25a60baa5..6ea09b031caf 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12.c @@ -217,7 +217,7 @@ static void update_mqd(struct mqd_manager *mm, void *mqd, * is safe, giving a maximum field value of 0xA. */ m->cp_hqd_eop_control = q->eop_ring_buffer_size ? min(0xA, - ffs(q->eop_ring_buffer_size / sizeof(unsigned int)) - 1 - 1) : 0; + ffs(q->eop_ring_buffer_size / sizeof(unsigned int) / 4)) : 0; m->cp_hqd_eop_base_addr_lo = lower_32_bits(q->eop_ring_buffer_address >> 8); m->cp_hqd_eop_base_addr_hi = diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12_1.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12_1.c index 708bbb08c089..c709db0210ce 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12_1.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v12_1.c @@ -295,7 +295,7 @@ static void update_mqd(struct mqd_manager *mm, void *mqd, * is safe, giving a maximum field value of 0xA. */ m->cp_hqd_eop_control = q->eop_ring_buffer_size ? min(0xA, - ffs(q->eop_ring_buffer_size / sizeof(unsigned int)) - 1 - 1) : 0; + ffs(q->eop_ring_buffer_size / sizeof(unsigned int) / 4)) : 0; m->cp_hqd_eop_base_addr_lo = lower_32_bits(q->eop_ring_buffer_address >> 8); m->cp_hqd_eop_base_addr_hi = |