On Fri, Dec 13, 2019 at 3:09 PM <mikita.lipski@xxxxxxx> wrote:
>
> From: Mikita Lipski <mikita.lipski@xxxxxxx>
>
Hi Mikita,
Unfortunately this patch causes a crash on my i915 device when I
unplug my MST hub. The panic is below.
[ 38.514014] BUG: kernel NULL pointer dereference, address: 0000000000000030
[ 38.521801] #PF: supervisor read access in kernel mode
[ 38.527556] #PF: error_code(0x0000) - not-present page
[ 38.533299] PGD 0 P4D 0
[ 38.536127] Oops: 0000 [#1] PREEMPT SMP PTI
[ 38.540798] CPU: 1 PID: 1324 Comm: DrmThread Not tainted
5.5.0-rc6-02273-g9bb4096398e7 #36
[ 38.550040] Hardware name: Google Fizz/Fizz, BIOS
Google_Fizz.10139.39.0 01/04/2018
[ 38.558606] RIP: 0010:drm_dp_mst_atomic_check_bw_limit+0x11/0x102
[ 38.565418] Code: 05 ff cb bf 19 48 f7 f6 c3 0f 1f 44 00 00 55 b8
0b 80 ff 0f 48 89 e5 5d c3 55 48 89 e5 41 57 41 56 41 55 41 54 4c 8d
77 30 53 <48> 8b 47 30 49 89 fd 49 89 f7 45 31 e4 48 8d 58 e8 48 8d 53
18 4c
[ 38.586422] RSP: 0018:ffffc9000139f9d8 EFLAGS: 00010282
[ 38.592264] RAX: 0000000000000000 RBX: ffff888272aeac88 RCX: ffff888236f529e0
[ 38.600242] RDX: ffff888272aeac88 RSI: ffff888236f529e0 RDI: 0000000000000000
[ 38.608220] RBP: ffffc9000139fa00 R08: 0000000000000031 R09: 000000000000000e
[ 38.616198] R10: ffff888236f529e8 R11: ffff8882621f3440 R12: 0000000000000000
[ 38.624176] R13: ffff888236f529d0 R14: 0000000000000030 R15: ffff888236f529e0
[ 38.632153] FS: 00007cd9229ce700(0000) GS:ffff888276c80000(0000)
knlGS:0000000000000000
[ 38.641193] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 38.647616] CR2: 0000000000000030 CR3: 00000002618e8004 CR4: 00000000003606e0
[ 38.655593] Call Trace:
[ 38.658329] drm_dp_mst_atomic_check+0x152/0x16d
[ 38.663484] intel_atomic_check+0xcfe/0x1e6f
[ 38.668259] ? trace_hardirqs_on+0x28/0x3d
[ 38.672835] ? intel_pipe_config_compare+0x1b38/0x1b38
[ 38.678580] drm_atomic_check_only+0x5ab/0x70f
[ 38.683547] ? drm_atomic_set_crtc_for_connector+0xf5/0x102
[ 38.689778] ? drm_atomic_helper_shutdown+0xb6/0xb6
[ 38.695221] drm_atomic_commit+0x18/0x53
[ 38.699604] drm_atomic_helper_set_config+0x5a/0x70
[ 38.705057] drm_mode_setcrtc+0x2ab/0x833
[ 38.709537] ? rcu_read_unlock+0x57/0x57
[ 38.713920] ? drm_mode_getcrtc+0x173/0x173
[ 38.718594] drm_ioctl+0x2e5/0x424
[ 38.722392] ? drm_mode_getcrtc+0x173/0x173
[ 38.727069] vfs_ioctl+0x21/0x2f
[ 38.730675] do_vfs_ioctl+0x5fb/0x61e
[ 38.734766] ksys_ioctl+0x55/0x75
[ 38.738469] __x64_sys_ioctl+0x1a/0x1e
[ 38.742659] do_syscall_64+0x5c/0x6d
[ 38.746653] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 38.752298] RIP: 0033:0x7cd92552d497
[ 38.756291] Code: 8a 66 90 48 8b 05 d1 d9 2b 00 64 c7 00 26 00 00
00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00
00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d9 2b 00 f7 d8 64 89
01 48
[ 38.777296] RSP: 002b:00007cd9229cd698 EFLAGS: 00000246 ORIG_RAX:
0000000000000010
[ 38.785762] RAX: ffffffffffffffda RBX: 000020323373da80 RCX: 00007cd92552d497
[ 38.793740] RDX: 00007cd9229cd6d0 RSI: 00000000c06864a2 RDI: 000000000000001c
[ 38.801717] RBP: 00007cd9229cd6c0 R08: 0000000000000000 R09: 0000000000000000
[ 38.809693] R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000001c
[ 38.817670] R13: 0000000000000000 R14: 00007cd9229cd6d0 R15: 00000000c06864a2
[ 38.825642] Modules linked in: xt_nat cdc_ether r8152 bridge stp
llc usbhid btusb btrtl btbcm btintel bluetooth asix usbnet
ecdh_generic ecc mii snd_soc_hdac_hdmi snd_soc_dmic xhci_pci xhci_hcd
snd_soc_skl snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_core
snd_intel_dspcfg snd_hda_core usbcore usb_common acpi_als kfifo_buf
industrialio xt_MASQUERADE iptable_nat nf_nat xt_mark fuse
ip6table_filter iwlmvm mac80211 r8169 realtek iwlwifi lzo_rle
lzo_compress zram cfg80211
[ 38.871839] CR2: 0000000000000030
[ 38.875542] ---[ end trace 6bb39ec52e30c7cb ]---
[ 38.886142] RIP: 0010:drm_dp_mst_atomic_check_bw_limit+0x11/0x102
[ 38.892957] Code: 05 ff cb bf 19 48 f7 f6 c3 0f 1f 44 00 00 55 b8
0b 80 ff 0f 48 89 e5 5d c3 55 48 89 e5 41 57 41 56 41 55 41 54 4c 8d
77 30 53 <48> 8b 47 30 49 89 fd 49 89 f7 45 31 e4 48 8d 58 e8 48 8d 53
18 4c
[ 38.913964] RSP: 0018:ffffc9000139f9d8 EFLAGS: 00010282
[ 38.919804] RAX: 0000000000000000 RBX: ffff888272aeac88 RCX: ffff888236f529e0
[ 38.927784] RDX: ffff888272aeac88 RSI: ffff888236f529e0 RDI: 0000000000000000
[ 38.935765] RBP: ffffc9000139fa00 R08: 0000000000000031 R09: 000000000000000e
[ 38.943733] R10: ffff888236f529e8 R11: ffff8882621f3440 R12: 0000000000000000
[ 38.951712] R13: ffff888236f529d0 R14: 0000000000000030 R15: ffff888236f529e0
[ 38.959692] FS: 00007cd9229ce700(0000) GS:ffff888276c80000(0000)
knlGS:0000000000000000
[ 38.968730] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 38.975144] CR2: 0000000000000030 CR3: 00000002618e8004 CR4: 00000000003606e0
[ 38.983121] Kernel panic - not syncing: Fatal exception
[ 38.988967] Kernel Offset: disabled
[ 38.998280] ---[ end Kernel panic - not syncing: Fatal exception ]---
> [why]
> Adding PBN attribute to drm_dp_vcpi_allocation structure to
> keep track of how much bandwidth each Port requires.
> Adding drm_dp_mst_atomic_check_bw_limit to verify that
> state's bandwidth needs doesn't exceed available bandwidth.
> The funtion is called in drm_dp_mst_atomic_check after
> drm_dp_mst_atomic_check_topology_state to fully verify that
> the proposed topology is supported.
>
> v2: Fixing some typos and indentations
>
> Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
> Signed-off-by: Mikita Lipski <mikita.lipski@xxxxxxx>
> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 66 ++++++++++++++++++++++++++-
> include/drm/drm_dp_mst_helper.h | 1 +
> 2 files changed, 65 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 7cd505e771ff..f8b72ac79c66 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4052,7 +4052,7 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
> {
> struct drm_dp_mst_topology_state *topology_state;
> struct drm_dp_vcpi_allocation *pos, *vcpi = NULL;
> - int prev_slots, req_slots;
> + int prev_slots, prev_bw, req_slots;
>
> topology_state = drm_atomic_get_mst_topology_state(state, mgr);
> if (IS_ERR(topology_state))
> @@ -4063,6 +4063,7 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
> if (pos->port == port) {
> vcpi = pos;
> prev_slots = vcpi->vcpi;
> + prev_bw = vcpi->pbn;
>
> /*
> * This should never happen, unless the driver tries
> @@ -4078,8 +4079,10 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
> break;
> }
> }
> - if (!vcpi)
> + if (!vcpi) {
> prev_slots = 0;
> + prev_bw = 0;
> + }
>
> if (pbn_div <= 0)
> pbn_div = mgr->pbn_div;
> @@ -4089,6 +4092,9 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
> DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] [MST PORT:%p] VCPI %d -> %d\n",
> port->connector->base.id, port->connector->name,
> port, prev_slots, req_slots);
> + DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] [MST PORT:%p] PBN %d -> %d\n",
> + port->connector->base.id, port->connector->name,
> + port, prev_bw, pbn);
>
> /* Add the new allocation to the state */
> if (!vcpi) {
> @@ -4101,6 +4107,7 @@ int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
> list_add(&vcpi->next, &topology_state->vcpis);
> }
> vcpi->vcpi = req_slots;
> + vcpi->pbn = pbn;
>
> return req_slots;
> }
> @@ -4677,6 +4684,58 @@ static void drm_dp_mst_destroy_state(struct drm_private_obj *obj,
> kfree(mst_state);
> }
>
> +static bool drm_dp_mst_port_downstream_of_branch(struct drm_dp_mst_port *port,
> + struct drm_dp_mst_branch *branch)
> +{
> + while (port->parent) {
> + if (port->parent == branch)
> + return true;
> +
> + if (port->parent->port_parent)
> + port = port->parent->port_parent;
> + else
> + break;
> + }
> + return false;
> +}
> +
> +static inline
> +int drm_dp_mst_atomic_check_bw_limit(struct drm_dp_mst_branch *branch,
> + struct drm_dp_mst_topology_state *mst_state)
> +{
> + struct drm_dp_mst_port *port;
> + struct drm_dp_vcpi_allocation *vcpi;
> + int pbn_limit = 0, pbn_used = 0;
> +
> + list_for_each_entry(port, &branch->ports, next) {
> + if (port->mstb)
> + if (drm_dp_mst_atomic_check_bw_limit(port->mstb, mst_state))
> + return -EINVAL;
> +
> + if (port->available_pbn > 0)
> + pbn_limit = port->available_pbn;
> + }
> + DRM_DEBUG_ATOMIC("[MST BRANCH:%p] branch has %d PBN available\n",
> + branch, pbn_limit);
> +
> + list_for_each_entry(vcpi, &mst_state->vcpis, next) {
> + if (!vcpi->pbn)
> + continue;
> +
> + if (drm_dp_mst_port_downstream_of_branch(vcpi->port, branch))
> + pbn_used += vcpi->pbn;
> + }
> + DRM_DEBUG_ATOMIC("[MST BRANCH:%p] branch used %d PBN\n",
> + branch, pbn_used);
> +
> + if (pbn_used > pbn_limit) {
> + DRM_DEBUG_ATOMIC("[MST BRANCH:%p] No available bandwidth\n",
> + branch);
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> static inline int
> drm_dp_mst_atomic_check_topology_state(struct drm_dp_mst_topology_mgr *mgr,
> struct drm_dp_mst_topology_state *mst_state)
> @@ -4808,6 +4867,9 @@ int drm_dp_mst_atomic_check(struct drm_atomic_state *state)
> ret = drm_dp_mst_atomic_check_topology_state(mgr, mst_state);
> if (ret)
> break;
> + ret = drm_dp_mst_atomic_check_bw_limit(mgr->mst_primary, mst_state);
> + if (ret)
> + break;
> }
>
> return ret;
> diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
> index 830c94b7f45d..2919d9776af3 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -502,6 +502,7 @@ struct drm_dp_payload {
> struct drm_dp_vcpi_allocation {
> struct drm_dp_mst_port *port;
> int vcpi;
> + int pbn;
> bool dsc_enabled;
> struct list_head next;
> };
> --
> 2.17.1
>
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