From c90521a0e94f00a2e40889b7d7d99f1494fa9381 Mon Sep 17 00:00:00 2001 From: Cristian Marussi Date: Mon, 16 Aug 2021 15:16:09 +0100 Subject: firmware: arm_scmi: Fix virtio transport Kconfig dependency ARM_SCMI_TRANSPORT_VIRTIO is a 'bool' Kconfig used to include support for the SCMI virtio transport inside the core SCMI stack; a bare transport dependency attached here to this option, though, cannot be properly propagated to the parent ARM_SCMI_PROTOCOL option and, as a result, it is currently possible to configure a Kernel where SCMI core is builtin and includes support for virtio while VirtIO core is =m. This allowed combination breaks linking: ARM_SCMI_PROTOCOL=y ARM_SCMI_TRANSPORT_VIRTIO=y VIRTIO=m Bind the dependency in ARM_SCMI_TRANSPORT_VIRTIO to the chosen kind of compilation of ARM_SCMI_PROTOCOL. Link: https://lore.kernel.org/r/20210816141609.41751-1-cristian.marussi@arm.com Fixes: 46abe13b5e3d ("firmware: arm_scmi: Add virtio transport") Reported-by: kernel test robot Suggested-by: Arnd Bergmann Acked-by: Arnd Bergmann Signed-off-by: Cristian Marussi Signed-off-by: Sudeep Holla --- drivers/firmware/arm_scmi/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig index 7f4d2435503b..3d7081e84853 100644 --- a/drivers/firmware/arm_scmi/Kconfig +++ b/drivers/firmware/arm_scmi/Kconfig @@ -68,7 +68,7 @@ config ARM_SCMI_TRANSPORT_SMC config ARM_SCMI_TRANSPORT_VIRTIO bool "SCMI transport based on VirtIO" - depends on VIRTIO + depends on VIRTIO=y || VIRTIO=ARM_SCMI_PROTOCOL select ARM_SCMI_HAVE_TRANSPORT select ARM_SCMI_HAVE_MSG help -- cgit v1.2.3 From 1cd73200dad2d53d839b3323596dbf8a2b949d86 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Mon, 20 Sep 2021 12:02:52 +0200 Subject: firmware: arm_scmi: Remove __exit annotation virtio_scmi_exit() is only called from __exit function, so the annotation is correct, but when the driver is built-in, the section gets discarded and the reference from a callback pointer causes a link-time error: `virtio_scmi_exit' referenced in section `.rodata' of drivers/firmware/arm_scmi/virtio.o: defined in discarded section `.exit.text' of drivers/firmware/arm_scmi/virtio.o I could not figure out a better workaround, so let's just remove that annotation even if it wastes a couple of bytes in .text. Link: https://lore.kernel.org/r/20210920100301.1466486-2-arnd@kernel.org Fixes: 46abe13b5e3d ("firmware: arm_scmi: Add virtio transport") Signed-off-by: Arnd Bergmann Signed-off-by: Sudeep Holla --- drivers/firmware/arm_scmi/virtio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c index 224577f86928..8941bb40f2df 100644 --- a/drivers/firmware/arm_scmi/virtio.c +++ b/drivers/firmware/arm_scmi/virtio.c @@ -476,7 +476,7 @@ static int __init virtio_scmi_init(void) return register_virtio_driver(&virtio_scmi_driver); } -static void __exit virtio_scmi_exit(void) +static void virtio_scmi_exit(void) { unregister_virtio_driver(&virtio_scmi_driver); } -- cgit v1.2.3 From a14a14595dcade4bf31e50909a6958ed2566c058 Mon Sep 17 00:00:00 2001 From: Cristian Marussi Date: Thu, 16 Sep 2021 11:33:35 +0100 Subject: firmware: arm_scmi: Simplify spinlocks in virtio transport Remove unneeded nested irqsave/irqrestore spinlocks. Add also a few descriptive comments to explain better the system behaviour at shutdown time. Link: https://lore.kernel.org/r/20210916103336.7243-2-cristian.marussi@arm.com Cc: "Michael S. Tsirkin" Cc: Sudeep Holla Signed-off-by: Cristian Marussi Signed-off-by: Sudeep Holla --- drivers/firmware/arm_scmi/virtio.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c index 8941bb40f2df..f3a1ef9bb2a6 100644 --- a/drivers/firmware/arm_scmi/virtio.c +++ b/drivers/firmware/arm_scmi/virtio.c @@ -110,18 +110,16 @@ static void scmi_finalize_message(struct scmi_vio_channel *vioch, if (vioch->is_rx) { scmi_vio_feed_vq_rx(vioch, msg); } else { - unsigned long flags; - - spin_lock_irqsave(&vioch->lock, flags); + /* Here IRQs are assumed to be already disabled by the caller */ + spin_lock(&vioch->lock); list_add(&msg->list, &vioch->free_list); - spin_unlock_irqrestore(&vioch->lock, flags); + spin_unlock(&vioch->lock); } } static void scmi_vio_complete_cb(struct virtqueue *vqueue) { unsigned long ready_flags; - unsigned long flags; unsigned int length; struct scmi_vio_channel *vioch; struct scmi_vio_msg *msg; @@ -140,7 +138,8 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) goto unlock_ready_out; } - spin_lock_irqsave(&vioch->lock, flags); + /* IRQs already disabled here no need to irqsave */ + spin_lock(&vioch->lock); if (cb_enabled) { virtqueue_disable_cb(vqueue); cb_enabled = false; @@ -151,7 +150,7 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) goto unlock_out; cb_enabled = true; } - spin_unlock_irqrestore(&vioch->lock, flags); + spin_unlock(&vioch->lock); if (msg) { msg->rx_len = length; @@ -161,11 +160,18 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) scmi_finalize_message(vioch, msg); } + /* + * Release ready_lock and re-enable IRQs between loop iterations + * to allow virtio_chan_free() to possibly kick in and set the + * flag vioch->ready to false even in between processing of + * messages, so as to force outstanding messages to be ignored + * when system is shutting down. + */ spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); } unlock_out: - spin_unlock_irqrestore(&vioch->lock, flags); + spin_unlock(&vioch->lock); unlock_ready_out: spin_unlock_irqrestore(&vioch->ready_lock, ready_flags); } @@ -435,6 +441,13 @@ static int scmi_vio_probe(struct virtio_device *vdev) static void scmi_vio_remove(struct virtio_device *vdev) { + /* + * Once we get here, virtio_chan_free() will have already been called by + * the SCMI core for any existing channel and, as a consequence, all the + * virtio channels will have been already marked NOT ready, causing any + * outstanding message on any vqueue to be ignored by complete_cb: now + * we can just stop processing buffers and destroy the vqueues. + */ vdev->config->reset(vdev); vdev->config->del_vqs(vdev); scmi_vdev = NULL; -- cgit v1.2.3 From bf1acf809d5694a942e113dfca6ef076d3904bb4 Mon Sep 17 00:00:00 2001 From: Cristian Marussi Date: Thu, 16 Sep 2021 11:33:36 +0100 Subject: firmware: arm_scmi: Add proper barriers to scmi virtio device Only one single SCMI Virtio device is currently supported by this driver and it is referenced using a static global variable which is initialized once for all during probing and nullified at virtio device removal. Add proper SMP barriers to protect accesses to such device reference to ensure that the initialzation state of such device is correctly observed by all PEs at any time. Return -EBUSY, instead of -EINVAL, and a descriptive error message if more than one SCMI Virtio device is ever found and probed. Link: https://lore.kernel.org/r/20210916103336.7243-3-cristian.marussi@arm.com Cc: "Michael S. Tsirkin" Cc: Sudeep Holla Signed-off-by: Cristian Marussi Signed-off-by: Sudeep Holla --- drivers/firmware/arm_scmi/virtio.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c index f3a1ef9bb2a6..11e8efb71375 100644 --- a/drivers/firmware/arm_scmi/virtio.c +++ b/drivers/firmware/arm_scmi/virtio.c @@ -390,8 +390,11 @@ static int scmi_vio_probe(struct virtio_device *vdev) struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT]; /* Only one SCMI VirtiO device allowed */ - if (scmi_vdev) - return -EINVAL; + if (scmi_vdev) { + dev_err(dev, + "One SCMI Virtio device was already initialized: only one allowed.\n"); + return -EBUSY; + } have_vq_rx = scmi_vio_have_vq_rx(vdev); vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1; @@ -434,7 +437,8 @@ static int scmi_vio_probe(struct virtio_device *vdev) } vdev->priv = channels; - scmi_vdev = vdev; + /* Ensure initialized scmi_vdev is visible */ + smp_store_mb(scmi_vdev, vdev); return 0; } @@ -450,7 +454,8 @@ static void scmi_vio_remove(struct virtio_device *vdev) */ vdev->config->reset(vdev); vdev->config->del_vqs(vdev); - scmi_vdev = NULL; + /* Ensure scmi_vdev is visible as NULL */ + smp_store_mb(scmi_vdev, NULL); } static int scmi_vio_validate(struct virtio_device *vdev) -- cgit v1.2.3