Re: [PATCH 2/7] KVM: s390: virtio-ccw adapter interrupt support.

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 25/02/14 18:24, Cornelia Huck wrote:
> Implement the new CCW_CMD_SET_IND_ADAPTER command and try to enable
> adapter interrupts for every device on the first startup. If the host
> does not support adapter interrupts, fall back to normal I/O interrupts.
> 
> virtio-ccw adapter interrupts use the same isc as normal I/O subchannels
> and share a summary indicator for all devices sharing the same indicator
> area.
> 
> Indicator bits for the individual virtqueues may be contained in the same
> indicator area for different devices.
> 
> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

This is s390 only code, so I will queue that for my next KVM:s390 pull request
(I will also queue patch 1. It is also in s390/features, but patch 2
needs it).

For everything else (irqfd etc) I prefer to have some review from the
other platforms, since we change common code.

Christian


> ---
>  arch/s390/include/asm/irq.h   |    1 +
>  arch/s390/kernel/irq.c        |    1 +
>  drivers/s390/kvm/virtio_ccw.c |  276 +++++++++++++++++++++++++++++++++++++++--
>  3 files changed, 268 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/s390/include/asm/irq.h b/arch/s390/include/asm/irq.h
> index 5f8bcc5..35f0faa 100644
> --- a/arch/s390/include/asm/irq.h
> +++ b/arch/s390/include/asm/irq.h
> @@ -53,6 +53,7 @@ enum interruption_class {
>  	IRQIO_PCI,
>  	IRQIO_MSI,
>  	IRQIO_VIR,
> +	IRQIO_VAI,
>  	NMI_NMI,
>  	CPU_RST,
>  	NR_ARCH_IRQS
> diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
> index bb27a26..c288ef7 100644
> --- a/arch/s390/kernel/irq.c
> +++ b/arch/s390/kernel/irq.c
> @@ -84,6 +84,7 @@ static const struct irq_class irqclass_sub_desc[NR_ARCH_IRQS] = {
>  	[IRQIO_PCI]  = {.name = "PCI", .desc = "[I/O] PCI Interrupt" },
>  	[IRQIO_MSI]  = {.name = "MSI", .desc = "[I/O] MSI Interrupt" },
>  	[IRQIO_VIR]  = {.name = "VIR", .desc = "[I/O] Virtual I/O Devices"},
> +	[IRQIO_VAI]  = {.name = "VAI", .desc = "[I/O] Virtual I/O Devices AI"},
>  	[NMI_NMI]    = {.name = "NMI", .desc = "[NMI] Machine Check"},
>  	[CPU_RST]    = {.name = "RST", .desc = "[CPU] CPU Restart"},
>  };
> diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
> index 0fc5848..09afefe 100644
> --- a/drivers/s390/kvm/virtio_ccw.c
> +++ b/drivers/s390/kvm/virtio_ccw.c
> @@ -1,7 +1,7 @@
>  /*
>   * ccw based virtio transport
>   *
> - * Copyright IBM Corp. 2012
> + * Copyright IBM Corp. 2012,2014
>   *
>   * This program is free software; you can redistribute it and/or modify
>   * it under the terms of the GNU General Public License (version 2 only)
> @@ -32,6 +32,8 @@
>  #include <asm/cio.h>
>  #include <asm/ccwdev.h>
>  #include <asm/virtio-ccw.h>
> +#include <asm/isc.h>
> +#include <asm/airq.h>
> 
>  /*
>   * virtio related functions
> @@ -58,6 +60,8 @@ struct virtio_ccw_device {
>  	unsigned long indicators;
>  	unsigned long indicators2;
>  	struct vq_config_block *config_block;
> +	bool is_thinint;
> +	void *airq_info;
>  };
> 
>  struct vq_info_block {
> @@ -72,15 +76,38 @@ struct virtio_feature_desc {
>  	__u8 index;
>  } __packed;
> 
> +struct virtio_thinint_area {
> +	unsigned long summary_indicator;
> +	unsigned long indicator;
> +	u64 bit_nr;
> +	u8 isc;
> +} __packed;
> +
>  struct virtio_ccw_vq_info {
>  	struct virtqueue *vq;
>  	int num;
>  	void *queue;
>  	struct vq_info_block *info_block;
> +	int bit_nr;
>  	struct list_head node;
>  	long cookie;
>  };
> 
> +#define VIRTIO_AIRQ_ISC IO_SCH_ISC /* inherit from subchannel */
> +
> +#define VIRTIO_IV_BITS (L1_CACHE_BYTES * 8)
> +#define MAX_AIRQ_AREAS 20
> +
> +static int virtio_ccw_use_airq = 1;
> +
> +struct airq_info {
> +	rwlock_t lock;
> +	u8 summary_indicator;
> +	struct airq_struct airq;
> +	struct airq_iv *aiv;
> +};
> +static struct airq_info *airq_areas[MAX_AIRQ_AREAS];
> +
>  #define CCW_CMD_SET_VQ 0x13
>  #define CCW_CMD_VDEV_RESET 0x33
>  #define CCW_CMD_SET_IND 0x43
> @@ -91,6 +118,7 @@ struct virtio_ccw_vq_info {
>  #define CCW_CMD_WRITE_CONF 0x21
>  #define CCW_CMD_WRITE_STATUS 0x31
>  #define CCW_CMD_READ_VQ_CONF 0x32
> +#define CCW_CMD_SET_IND_ADAPTER 0x73
> 
>  #define VIRTIO_CCW_DOING_SET_VQ 0x00010000
>  #define VIRTIO_CCW_DOING_RESET 0x00040000
> @@ -102,6 +130,7 @@ struct virtio_ccw_vq_info {
>  #define VIRTIO_CCW_DOING_SET_IND 0x01000000
>  #define VIRTIO_CCW_DOING_READ_VQ_CONF 0x02000000
>  #define VIRTIO_CCW_DOING_SET_CONF_IND 0x04000000
> +#define VIRTIO_CCW_DOING_SET_IND_ADAPTER 0x08000000
>  #define VIRTIO_CCW_INTPARM_MASK 0xffff0000
> 
>  static struct virtio_ccw_device *to_vc_device(struct virtio_device *vdev)
> @@ -109,6 +138,125 @@ static struct virtio_ccw_device *to_vc_device(struct virtio_device *vdev)
>  	return container_of(vdev, struct virtio_ccw_device, vdev);
>  }
> 
> +static void drop_airq_indicator(struct virtqueue *vq, struct airq_info *info)
> +{
> +	unsigned long i, flags;
> +
> +	write_lock_irqsave(&info->lock, flags);
> +	for (i = 0; i < airq_iv_end(info->aiv); i++) {
> +		if (vq == (void *)airq_iv_get_ptr(info->aiv, i)) {
> +			airq_iv_free_bit(info->aiv, i);
> +			airq_iv_set_ptr(info->aiv, i, 0);
> +			break;
> +		}
> +	}
> +	write_unlock_irqrestore(&info->lock, flags);
> +}
> +
> +static void virtio_airq_handler(struct airq_struct *airq)
> +{
> +	struct airq_info *info = container_of(airq, struct airq_info, airq);
> +	unsigned long ai;
> +
> +	inc_irq_stat(IRQIO_VAI);
> +	read_lock(&info->lock);
> +	/* Walk through indicators field, summary indicator active. */
> +	for (ai = 0;;) {
> +		ai = airq_iv_scan(info->aiv, ai, airq_iv_end(info->aiv));
> +		if (ai == -1UL)
> +			break;
> +		vring_interrupt(0, (void *)airq_iv_get_ptr(info->aiv, ai));
> +	}
> +	info->summary_indicator = 0;
> +	smp_wmb();
> +	/* Walk through indicators field, summary indicator not active. */
> +	for (ai = 0;;) {
> +		ai = airq_iv_scan(info->aiv, ai, airq_iv_end(info->aiv));
> +		if (ai == -1UL)
> +			break;
> +		vring_interrupt(0, (void *)airq_iv_get_ptr(info->aiv, ai));
> +	}
> +	read_unlock(&info->lock);
> +}
> +
> +static struct airq_info *new_airq_info(void)
> +{
> +	struct airq_info *info;
> +	int rc;
> +
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (!info)
> +		return NULL;
> +	rwlock_init(&info->lock);
> +	info->aiv = airq_iv_create(VIRTIO_IV_BITS, AIRQ_IV_ALLOC | AIRQ_IV_PTR);
> +	if (!info->aiv) {
> +		kfree(info);
> +		return NULL;
> +	}
> +	info->airq.handler = virtio_airq_handler;
> +	info->airq.lsi_ptr = &info->summary_indicator;
> +	info->airq.lsi_mask = 0xff;
> +	info->airq.isc = VIRTIO_AIRQ_ISC;
> +	rc = register_adapter_interrupt(&info->airq);
> +	if (rc) {
> +		airq_iv_release(info->aiv);
> +		kfree(info);
> +		return NULL;
> +	}
> +	return info;
> +}
> +
> +static void destroy_airq_info(struct airq_info *info)
> +{
> +	if (!info)
> +		return;
> +
> +	unregister_adapter_interrupt(&info->airq);
> +	airq_iv_release(info->aiv);
> +	kfree(info);
> +}
> +
> +static unsigned long get_airq_indicator(struct virtqueue *vqs[], int nvqs,
> +					u64 *first, void **airq_info)
> +{
> +	int i, j;
> +	struct airq_info *info;
> +	unsigned long indicator_addr = 0;
> +	unsigned long bit, flags;
> +
> +	for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) {
> +		if (!airq_areas[i])
> +			airq_areas[i] = new_airq_info();
> +		info = airq_areas[i];
> +		if (!info)
> +			return 0;
> +		write_lock_irqsave(&info->lock, flags);
> +		bit = airq_iv_alloc(info->aiv, nvqs);
> +		if (bit == -1UL) {
> +			/* Not enough vacancies. */
> +			write_unlock_irqrestore(&info->lock, flags);
> +			continue;
> +		}
> +		*first = bit;
> +		*airq_info = info;
> +		indicator_addr = (unsigned long)info->aiv->vector;
> +		for (j = 0; j < nvqs; j++) {
> +			airq_iv_set_ptr(info->aiv, bit + j,
> +					(unsigned long)vqs[j]);
> +		}
> +		write_unlock_irqrestore(&info->lock, flags);
> +	}
> +	return indicator_addr;
> +}
> +
> +static void virtio_ccw_drop_indicators(struct virtio_ccw_device *vcdev)
> +{
> +	struct virtio_ccw_vq_info *info;
> +
> +	list_for_each_entry(info, &vcdev->virtqueues, node)
> +		drop_airq_indicator(info->vq, vcdev->airq_info);
> +}
> +
>  static int doing_io(struct virtio_ccw_device *vcdev, __u32 flag)
>  {
>  	unsigned long flags;
> @@ -145,6 +293,51 @@ static int ccw_io_helper(struct virtio_ccw_device *vcdev,
>  	return ret ? ret : vcdev->err;
>  }
> 
> +static void virtio_ccw_drop_indicator(struct virtio_ccw_device *vcdev,
> +				      struct ccw1 *ccw)
> +{
> +	int ret;
> +	unsigned long *indicatorp = NULL;
> +	struct virtio_thinint_area *thinint_area = NULL;
> +	struct airq_info *airq_info = vcdev->airq_info;
> +
> +	if (vcdev->is_thinint) {
> +		thinint_area = kzalloc(sizeof(*thinint_area),
> +				       GFP_DMA | GFP_KERNEL);
> +		if (!thinint_area)
> +			return;
> +		thinint_area->summary_indicator =
> +			(unsigned long) &airq_info->summary_indicator;
> +		thinint_area->isc = VIRTIO_AIRQ_ISC;
> +		ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
> +		ccw->count = sizeof(*thinint_area);
> +		ccw->cda = (__u32)(unsigned long) thinint_area;
> +	} else {
> +		indicatorp = kmalloc(sizeof(&vcdev->indicators),
> +				     GFP_DMA | GFP_KERNEL);
> +		if (!indicatorp)
> +			return;
> +		*indicatorp = 0;
> +		ccw->cmd_code = CCW_CMD_SET_IND;
> +		ccw->count = sizeof(vcdev->indicators);
> +		ccw->cda = (__u32)(unsigned long) indicatorp;
> +	}
> +	/* Deregister indicators from host. */
> +	vcdev->indicators = 0;
> +	ccw->flags = 0;
> +	ret = ccw_io_helper(vcdev, ccw,
> +			    vcdev->is_thinint ?
> +			    VIRTIO_CCW_DOING_SET_IND_ADAPTER :
> +			    VIRTIO_CCW_DOING_SET_IND);
> +	if (ret && (ret != -ENODEV))
> +		dev_info(&vcdev->cdev->dev,
> +			 "Failed to deregister indicators (%d)\n", ret);
> +	else if (vcdev->is_thinint)
> +		virtio_ccw_drop_indicators(vcdev);
> +	kfree(indicatorp);
> +	kfree(thinint_area);
> +}
> +
>  static inline long do_kvm_notify(struct subchannel_id schid,
>  				 unsigned long queue_index,
>  				 long cookie)
> @@ -232,11 +425,13 @@ static void virtio_ccw_del_vqs(struct virtio_device *vdev)
>  {
>  	struct virtqueue *vq, *n;
>  	struct ccw1 *ccw;
> +	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
> 
>  	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
>  	if (!ccw)
>  		return;
> 
> +	virtio_ccw_drop_indicator(vcdev, ccw);
> 
>  	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
>  		virtio_ccw_del_vq(vq, ccw);
> @@ -326,6 +521,52 @@ out_err:
>  	return ERR_PTR(err);
>  }
> 
> +static int virtio_ccw_register_adapter_ind(struct virtio_ccw_device *vcdev,
> +					   struct virtqueue *vqs[], int nvqs,
> +					   struct ccw1 *ccw)
> +{
> +	int ret;
> +	struct virtio_thinint_area *thinint_area = NULL;
> +	struct airq_info *info;
> +
> +	thinint_area = kzalloc(sizeof(*thinint_area), GFP_DMA | GFP_KERNEL);
> +	if (!thinint_area) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +	/* Try to get an indicator. */
> +	thinint_area->indicator = get_airq_indicator(vqs, nvqs,
> +						     &thinint_area->bit_nr,
> +						     &vcdev->airq_info);
> +	if (!thinint_area->indicator) {
> +		ret = -ENOSPC;
> +		goto out;
> +	}
> +	info = vcdev->airq_info;
> +	thinint_area->summary_indicator =
> +		(unsigned long) &info->summary_indicator;
> +	thinint_area->isc = VIRTIO_AIRQ_ISC;
> +	ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
> +	ccw->flags = CCW_FLAG_SLI;
> +	ccw->count = sizeof(*thinint_area);
> +	ccw->cda = (__u32)(unsigned long)thinint_area;
> +	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_SET_IND_ADAPTER);
> +	if (ret) {
> +		dev_warn(&vcdev->cdev->dev,
> +			 "enabling adapter interrupts = %d\n", ret);
> +		if (ret == -EOPNOTSUPP)
> +			/*
> +			 * The host does not support adapter interrupts
> +			 * for virtio-ccw, stop trying.
> +			 */
> +			virtio_ccw_use_airq = 0;
> +		virtio_ccw_drop_indicators(vcdev);
> +	}
> +out:
> +	kfree(thinint_area);
> +	return ret;
> +}
> +
>  static int virtio_ccw_find_vqs(struct virtio_device *vdev, unsigned nvqs,
>  			       struct virtqueue *vqs[],
>  			       vq_callback_t *callbacks[],
> @@ -355,15 +596,23 @@ static int virtio_ccw_find_vqs(struct virtio_device *vdev, unsigned nvqs,
>  	if (!indicatorp)
>  		goto out;
>  	*indicatorp = (unsigned long) &vcdev->indicators;
> -	/* Register queue indicators with host. */
> -	vcdev->indicators = 0;
> -	ccw->cmd_code = CCW_CMD_SET_IND;
> -	ccw->flags = 0;
> -	ccw->count = sizeof(vcdev->indicators);
> -	ccw->cda = (__u32)(unsigned long) indicatorp;
> -	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_SET_IND);
> -	if (ret)
> -		goto out;
> +	if (vcdev->is_thinint) {
> +		ret = virtio_ccw_register_adapter_ind(vcdev, vqs, nvqs, ccw);
> +		if (ret)
> +			/* no error, just fall back to legacy interrupts */
> +			vcdev->is_thinint = 0;
> +	}
> +	if (!vcdev->is_thinint) {
> +		/* Register queue indicators with host. */
> +		vcdev->indicators = 0;
> +		ccw->cmd_code = CCW_CMD_SET_IND;
> +		ccw->flags = 0;
> +		ccw->count = sizeof(vcdev->indicators);
> +		ccw->cda = (__u32)(unsigned long) indicatorp;
> +		ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_SET_IND);
> +		if (ret)
> +			goto out;
> +	}
>  	/* Register indicators2 with host for config changes */
>  	*indicatorp = (unsigned long) &vcdev->indicators2;
>  	vcdev->indicators2 = 0;
> @@ -663,6 +912,7 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
>  		case VIRTIO_CCW_DOING_SET_CONF_IND:
>  		case VIRTIO_CCW_DOING_RESET:
>  		case VIRTIO_CCW_DOING_READ_VQ_CONF:
> +		case VIRTIO_CCW_DOING_SET_IND_ADAPTER:
>  			vcdev->curr_io &= ~activity;
>  			wake_up(&vcdev->wait_q);
>  			break;
> @@ -778,6 +1028,8 @@ static int virtio_ccw_online(struct ccw_device *cdev)
>  		goto out_free;
>  	}
> 
> +	vcdev->is_thinint = virtio_ccw_use_airq; /* at least try */
> +
>  	vcdev->vdev.dev.parent = &cdev->dev;
>  	vcdev->vdev.dev.release = virtio_ccw_release_dev;
>  	vcdev->vdev.config = &virtio_ccw_config_ops;
> @@ -935,6 +1187,10 @@ module_init(virtio_ccw_init);
> 
>  static void __exit virtio_ccw_exit(void)
>  {
> +	int i;
> +
>  	ccw_driver_unregister(&virtio_ccw_driver);
> +	for (i = 0; i < MAX_AIRQ_AREAS; i++)
> +		destroy_airq_info(airq_areas[i]);
>  }
>  module_exit(virtio_ccw_exit);
>