Date:   Tue, 15 Feb 2022 10:16:59 +0800
From:   "Zhu, Lingshan" <lingshan.zhu@...el.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>
Cc:     netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH V4 4/4] vDPA/ifcvf: implement shared IRQ feature



On 2/14/2022 10:25 PM, Michael S. Tsirkin wrote:
> On Mon, Feb 14, 2022 at 03:19:25PM +0800, Jason Wang wrote:
>> 在 2022/2/3 下午3:27, Zhu Lingshan 写道:
>>> On some platforms/devices, there may not be enough MSI vector
>>> slots allocated for virtqueues and config changes. In such a case,
>>> the interrupt sources(virtqueues, config changes) must share
>>> an IRQ/vector, to avoid initialization failures, keep
>>> the device functional.
>>>
>>> This commit handles three cases:
>>> (1) number of the allocated vectors == the number of virtqueues + 1
>>> (config changes), every virtqueue and the config interrupt has
>>> a separated vector/IRQ, the best and the most likely case.
>>> (2) number of the allocated vectors is less than the best case, but
>>> greater than 1. In this case, all virtqueues share a vector/IRQ,
>>> the config interrupt has a separated vector/IRQ
>>> (3) only one vector is allocated, in this case, the virtqueues and
>>> the config interrupt share a vector/IRQ. The worst and most
>>> unlikely case.
>>>
>>> Otherwise, it needs to fail.
>>>
>>> This commit introduces some helper functions:
>>> ifcvf_set_vq_vector() and ifcvf_set_config_vector() sets virtqueue
>>> vector and config vector in the device config space, so that
>>> the device can send interrupt DMA.
>>>
>>> This commit adds some fields in struct ifcvf_hw and re-placed
>>> the existed fields to be aligned with the cacheline.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>> ---
>>>    drivers/vdpa/ifcvf/ifcvf_base.c |  47 ++++--
>>>    drivers/vdpa/ifcvf/ifcvf_base.h |  23 ++-
>>>    drivers/vdpa/ifcvf/ifcvf_main.c | 243 +++++++++++++++++++++++++++-----
>>>    3 files changed, 256 insertions(+), 57 deletions(-)
>>>
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.c b/drivers/vdpa/ifcvf/ifcvf_base.c
>>> index 397692ae671c..18dcb63ab1e3 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_base.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_base.c
>>> @@ -15,6 +15,36 @@ struct ifcvf_adapter *vf_to_adapter(struct ifcvf_hw *hw)
>>>    	return container_of(hw, struct ifcvf_adapter, vf);
>>>    }
>>> +int ifcvf_set_vq_vector(struct ifcvf_hw *hw, u16 qid, int vector)
>>> +{
>>> +	struct virtio_pci_common_cfg __iomem *cfg = hw->common_cfg;
>>> +	struct ifcvf_adapter *ifcvf = vf_to_adapter(hw);
>>> +
>>> +	ifc_iowrite16(qid, &cfg->queue_select);
>>> +	ifc_iowrite16(vector, &cfg->queue_msix_vector);
>>> +	if (ifc_ioread16(&cfg->queue_msix_vector) == VIRTIO_MSI_NO_VECTOR) {
>>> +		IFCVF_ERR(ifcvf->pdev, "No msix vector for queue %u\n", qid);
>>> +			return -EINVAL;
>>> +	}
>>
>> Let's leave this check for the caller, E.g can caller try to assign
>> NO_VECTOR during uni-nit?
>
> Hmm I'm not sure I agree. Caller will have to write queue select
> again, and that's an extra IO, which is a waste.
> And having function checking itself just seems better contained.
>
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +int ifcvf_set_config_vector(struct ifcvf_hw *hw, int vector)
>>> +{
>>> +	struct virtio_pci_common_cfg __iomem *cfg = hw->common_cfg;
>>> +	struct ifcvf_adapter *ifcvf = vf_to_adapter(hw);
>>> +
>>> +	cfg = hw->common_cfg;
>>> +	ifc_iowrite16(vector,  &cfg->msix_config);
>>> +	if (ifc_ioread16(&cfg->msix_config) == VIRTIO_MSI_NO_VECTOR) {
>>> +		IFCVF_ERR(ifcvf->pdev, "No msix vector for device config\n");
>>> +		return -EINVAL;
>>> +	}
>>
>> Similar question as above.
>>
>>
>>> +
>>> +	return 0;
>>> +}
>>> +
>>>    static void __iomem *get_cap_addr(struct ifcvf_hw *hw,
>>>    				  struct virtio_pci_cap *cap)
>>>    {
>>> @@ -140,6 +170,8 @@ int ifcvf_init_hw(struct ifcvf_hw *hw, struct pci_dev *pdev)
>>>    		  hw->common_cfg, hw->notify_base, hw->isr,
>>>    		  hw->dev_cfg, hw->notify_off_multiplier);
>>> +	hw->vqs_shared_irq = -EINVAL;
>>> +
>>>    	return 0;
>>>    }
>>> @@ -321,12 +353,6 @@ static int ifcvf_hw_enable(struct ifcvf_hw *hw)
>>>    	ifcvf = vf_to_adapter(hw);
>>>    	cfg = hw->common_cfg;
>>> -	ifc_iowrite16(IFCVF_MSI_CONFIG_OFF, &cfg->msix_config);
>>> -
>>> -	if (ifc_ioread16(&cfg->msix_config) == VIRTIO_MSI_NO_VECTOR) {
>>> -		IFCVF_ERR(ifcvf->pdev, "No msix vector for device config\n");
>>> -		return -EINVAL;
>>> -	}
>>>    	for (i = 0; i < hw->nr_vring; i++) {
>>>    		if (!hw->vring[i].ready)
>>> @@ -340,15 +366,6 @@ static int ifcvf_hw_enable(struct ifcvf_hw *hw)
>>>    		ifc_iowrite64_twopart(hw->vring[i].used, &cfg->queue_used_lo,
>>>    				     &cfg->queue_used_hi);
>>>    		ifc_iowrite16(hw->vring[i].size, &cfg->queue_size);
>>> -		ifc_iowrite16(i + IFCVF_MSI_QUEUE_OFF, &cfg->queue_msix_vector);
>>> -
>>> -		if (ifc_ioread16(&cfg->queue_msix_vector) ==
>>> -		    VIRTIO_MSI_NO_VECTOR) {
>>> -			IFCVF_ERR(ifcvf->pdev,
>>> -				  "No msix vector for queue %u\n", i);
>>> -			return -EINVAL;
>>> -		}
>>> -
>>>    		ifcvf_set_vq_state(hw, i, hw->vring[i].last_avail_idx);
>>>    		ifc_iowrite16(1, &cfg->queue_enable);
>>>    	}
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h b/drivers/vdpa/ifcvf/ifcvf_base.h
>>> index 949b4fb9d554..9cfe088c82e9 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_base.h
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
>>> @@ -27,8 +27,6 @@
>>>    #define IFCVF_QUEUE_ALIGNMENT	PAGE_SIZE
>>>    #define IFCVF_QUEUE_MAX		32768
>>> -#define IFCVF_MSI_CONFIG_OFF	0
>>> -#define IFCVF_MSI_QUEUE_OFF	1
>>>    #define IFCVF_PCI_MAX_RESOURCE	6
>>>    #define IFCVF_LM_CFG_SIZE		0x40
>>> @@ -42,6 +40,13 @@
>>>    #define ifcvf_private_to_vf(adapter) \
>>>    	(&((struct ifcvf_adapter *)adapter)->vf)
>>> +/* all vqs and config interrupt has its own vector */
>>> +#define MSIX_VECTOR_PER_VQ_AND_CONFIG		1
>>> +/* all vqs share a vector, and config interrupt has a separate vector */
>>> +#define MSIX_VECTOR_SHARED_VQ_AND_CONFIG	2
>>> +/* all vqs and config interrupt share a vector */
>>> +#define MSIX_VECTOR_DEV_SHARED			3
>>
>> I think there's no much value to differ 2 from 3 consider config interrupt
>> should be rare.
>
> Yes but if we do not have a dedicated vector then we need an
> extra device IO (in fact, a read) on each interrupt.
>
>>> +
>>>    static inline u8 ifc_ioread8(u8 __iomem *addr)
>>>    {
>>>    	return ioread8(addr);
>>> @@ -97,25 +102,27 @@ struct ifcvf_hw {
>>>    	u8 __iomem *isr;
>>>    	/* Live migration */
>>>    	u8 __iomem *lm_cfg;
>>> -	u16 nr_vring;
>>
>> Any reason for moving nv_vring, config_size, and other stuffs?
>>
>>
>>>    	/* Notification bar number */
>>>    	u8 notify_bar;
>>> +	u8 msix_vector_status;
>>> +	/* virtio-net or virtio-blk device config size */
>>> +	u32 config_size;
>>>    	/* Notificaiton bar address */
>>>    	void __iomem *notify_base;
>>>    	phys_addr_t notify_base_pa;
>>>    	u32 notify_off_multiplier;
>>> +	u32 dev_type;
>>>    	u64 req_features;
>>>    	u64 hw_features;
>>> -	u32 dev_type;
>>>    	struct virtio_pci_common_cfg __iomem *common_cfg;
>>>    	void __iomem *dev_cfg;
>>>    	struct vring_info vring[IFCVF_MAX_QUEUES];
>>>    	void __iomem * const *base;
>>>    	char config_msix_name[256];
>>>    	struct vdpa_callback config_cb;
>>> -	unsigned int config_irq;
>>> -	/* virtio-net or virtio-blk device config size */
>>> -	u32 config_size;
>>> +	int config_irq;
>>> +	int vqs_shared_irq;
>>> +	u16 nr_vring;
>>>    };
>>>    struct ifcvf_adapter {
>>> @@ -160,4 +167,6 @@ int ifcvf_set_vq_state(struct ifcvf_hw *hw, u16 qid, u16 num);
>>>    struct ifcvf_adapter *vf_to_adapter(struct ifcvf_hw *hw);
>>>    int ifcvf_probed_virtio_net(struct ifcvf_hw *hw);
>>>    u32 ifcvf_get_config_size(struct ifcvf_hw *hw);
>>> +int ifcvf_set_vq_vector(struct ifcvf_hw *hw, u16 qid, int vector);
>>> +int ifcvf_set_config_vector(struct ifcvf_hw *hw, int vector);
>>>    #endif /* _IFCVF_H_ */
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> index 44c89ab0b6da..ca414399f040 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> @@ -17,6 +17,7 @@
>>>    #define DRIVER_AUTHOR   "Intel Corporation"
>>>    #define IFCVF_DRIVER_NAME       "ifcvf"
>>> +/* handles config interrupt */
>>
>> This seems unrelated to the shared IRQ logic and it looks useless since it's
>> easily to deduce it from the function name below.
>>
>>
>>>    static irqreturn_t ifcvf_config_changed(int irq, void *arg)
>>>    {
>>>    	struct ifcvf_hw *vf = arg;
>>> @@ -27,6 +28,7 @@ static irqreturn_t ifcvf_config_changed(int irq, void *arg)
>>>    	return IRQ_HANDLED;
>>>    }
>>> +/* handles vqs interrupt */
>>
>> So did this.
>>
>>
>>>    static irqreturn_t ifcvf_intr_handler(int irq, void *arg)
>>>    {
>>>    	struct vring_info *vring = arg;
>>> @@ -37,24 +39,78 @@ static irqreturn_t ifcvf_intr_handler(int irq, void *arg)
>>>    	return IRQ_HANDLED;
>>>    }
>>> +/* handls vqs shared interrupt */
>>> +static irqreturn_t ifcvf_vq_shared_intr_handler(int irq, void *arg)
>>> +{
>>> +	struct ifcvf_hw *vf = arg;
>>> +	struct vring_info *vring;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < vf->nr_vring; i++) {
>>> +		vring = &vf->vring[i];
>>> +		if (vring->cb.callback)
>>> +			vf->vring->cb.callback(vring->cb.private);
>>> +	}
>>> +
>>> +	return IRQ_HANDLED;
>>> +}
>>> +
>>> +/* handles a shared interrupt for vqs and config */
>>> +static irqreturn_t ifcvf_dev_shared_intr_handler(int irq, void *arg)
> shared is not a good name given IRQ_SHARED is not set.
> maybe "common"? "reused"?
Sure, I can do better naming

Thanks
>
>>> +{
>>> +	struct ifcvf_hw *vf = arg;
>>> +	u8 isr;
>>> +
>>> +	isr = ifc_ioread8(vf->isr);
>>
>> We need to exactly what vp_interrupt do here. Checking against vf->isr first
>> and return IRQ_NONE if it is not set.
> no, vf->isr is not set for VQ interrupts. If need to actually poke
> at the VQ to know.
>
>> Always return IRQ_HANDLED will break the device who shares an irq with
>> IFCVF.
>
> It's a MSI, not INT#. So interrupt is not shared as such - it's only
> sharing vector between config and vq.
>
>
>>> +	if (isr & VIRTIO_PCI_ISR_CONFIG)
>>> +		ifcvf_config_changed(irq, arg);
>>> +
>>> +	return ifcvf_vq_shared_intr_handler(irq, arg);
>>> +}
>>> +
>>>    static void ifcvf_free_irq_vectors(void *data)
>>>    {
>>>    	pci_free_irq_vectors(data);
>>>    }
>>> -static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
>>> +static void ifcvf_free_vq_irq(struct ifcvf_adapter *adapter, int queues)
>>>    {
>>>    	struct pci_dev *pdev = adapter->pdev;
>>>    	struct ifcvf_hw *vf = &adapter->vf;
>>>    	int i;
>>> +	if (vf->msix_vector_status == MSIX_VECTOR_PER_VQ_AND_CONFIG) {
>>> +		for (i = 0; i < queues; i++) {
>>> +			devm_free_irq(&pdev->dev, vf->vring[i].irq, &vf->vring[i]);
>>> +			vf->vring[i].irq = -EINVAL;
>>> +		}
>>> +	} else {
>>> +		devm_free_irq(&pdev->dev, vf->vqs_shared_irq, vf);
>>> +		vf->vqs_shared_irq = -EINVAL;
>>> +	}
>>> +}
>>> -	for (i = 0; i < queues; i++) {
>>> -		devm_free_irq(&pdev->dev, vf->vring[i].irq, &vf->vring[i]);
>>> -		vf->vring[i].irq = -EINVAL;
>>> +static void ifcvf_free_config_irq(struct ifcvf_adapter *adapter)
>>> +{
>>> +	struct pci_dev *pdev = adapter->pdev;
>>> +	struct ifcvf_hw *vf = &adapter->vf;
>>> +
>>> +	/* If the irq is shared by all vqs and the config interrupt,
>>> +	 * it is already freed in ifcvf_free_vq_irq, so here only
>>> +	 * need to free config irq when msix_vector_status != MSIX_VECTOR_DEV_SHARED
>>> +	 */
>>> +	if (vf->msix_vector_status != MSIX_VECTOR_DEV_SHARED) {
>>> +		devm_free_irq(&pdev->dev, vf->config_irq, vf);
>>> +		vf->config_irq = -EINVAL;
>>>    	}
>>> +}
>>> +
>>> +static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
>>> +{
>>> +	struct pci_dev *pdev = adapter->pdev;
>>> -	devm_free_irq(&pdev->dev, vf->config_irq, vf);
>>> +	ifcvf_free_vq_irq(adapter, queues);
>>> +	ifcvf_free_config_irq(adapter);
>>>    	ifcvf_free_irq_vectors(pdev);
>>>    }
>>> @@ -86,58 +142,172 @@ static int ifcvf_alloc_vectors(struct ifcvf_adapter *adapter)
>>>    	return ret;
>>>    }
>>> -static int ifcvf_request_irq(struct ifcvf_adapter *adapter)
>>> +static int ifcvf_request_per_vq_irq(struct ifcvf_adapter *adapter)
>>>    {
>>>    	struct pci_dev *pdev = adapter->pdev;
>>>    	struct ifcvf_hw *vf = &adapter->vf;
>>> -	int vector, nvectors, i, ret, irq;
>>> -	u16 max_intr;
>>> +	int i, vector, ret, irq;
>>> -	nvectors = ifcvf_alloc_vectors(adapter);
>>> -	if (!(nvectors > 0))
>>> -		return nvectors;
>>> +	for (i = 0; i < vf->nr_vring; i++) {
>>> +		snprintf(vf->vring[i].msix_name, 256, "ifcvf[%s]-%d\n", pci_name(pdev), i);
>>> +		vector = i;
>>> +		irq = pci_irq_vector(pdev, vector);
>>> +		ret = devm_request_irq(&pdev->dev, irq,
>>> +				       ifcvf_intr_handler, 0,
>>> +				       vf->vring[i].msix_name,
>>> +				       &vf->vring[i]);
>>> +		if (ret) {
>>> +			IFCVF_ERR(pdev, "Failed to request irq for vq %d\n", i);
>>> +			ifcvf_free_vq_irq(adapter, i);
>>> +		} else {
>>> +			vf->vring[i].irq = irq;
>>> +			ifcvf_set_vq_vector(vf, i, vector);
>>> +		}
>>> +	}
>>> -	max_intr = vf->nr_vring + 1;
>>> +	vf->vqs_shared_irq = -EINVAL;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int ifcvf_request_shared_vq_irq(struct ifcvf_adapter *adapter)
>>> +{
>>> +	struct pci_dev *pdev = adapter->pdev;
>>> +	struct ifcvf_hw *vf = &adapter->vf;
>>> +	int i, vector, ret, irq;
>>> +
>>> +	vector = 0;
>>> +	/* reuse msix_name[256] space of vring0 to store shared vqs interrupt name */
>>
>> I think we can remove this comment since the code is straightforward.
>>
>>
>>> +	snprintf(vf->vring[0].msix_name, 256, "ifcvf[%s]-vqs-shared-irq\n", pci_name(pdev));
>>> +	irq = pci_irq_vector(pdev, vector);
>>> +	ret = devm_request_irq(&pdev->dev, irq,
>>> +			       ifcvf_vq_shared_intr_handler, 0,
>>> +			       vf->vring[0].msix_name, vf);
>>> +	if (ret) {
>>> +		IFCVF_ERR(pdev, "Failed to request shared irq for vf\n");
>>> +
>>> +		return ret;
>>> +	}
>>> +
>>> +	vf->vqs_shared_irq = irq;
>>> +	for (i = 0; i < vf->nr_vring; i++) {
>>> +		vf->vring[i].irq = -EINVAL;
>>> +		ifcvf_set_vq_vector(vf, i, vector);
>>> +	}
>>> +
>>> +	return 0;
>>> +
>>> +}
>>> +
>>> +static int ifcvf_request_dev_shared_irq(struct ifcvf_adapter *adapter)
>>> +{
>>> +	struct pci_dev *pdev = adapter->pdev;
>>> +	struct ifcvf_hw *vf = &adapter->vf;
>>> +	int i, vector, ret, irq;
>>> +
>>> +	vector = 0;
>>> +	/* reuse msix_name[256] space of vring0 to store shared device interrupt name */
>>> +	snprintf(vf->vring[0].msix_name, 256, "ifcvf[%s]-dev-shared-irq\n", pci_name(pdev));
>>> +	irq = pci_irq_vector(pdev, vector);
>>> +	ret = devm_request_irq(&pdev->dev, irq,
>>> +			       ifcvf_dev_shared_intr_handler, 0,
>>> +			       vf->vring[0].msix_name, vf);
>>> +	if (ret) {
>>> +		IFCVF_ERR(pdev, "Failed to request shared irq for vf\n");
>>> -	ret = pci_alloc_irq_vectors(pdev, max_intr,
>>> -				    max_intr, PCI_IRQ_MSIX);
>>> -	if (ret < 0) {
>>> -		IFCVF_ERR(pdev, "Failed to alloc IRQ vectors\n");
>>>    		return ret;
>>>    	}
>>> +	vf->vqs_shared_irq = irq;
>>> +	for (i = 0; i < vf->nr_vring; i++) {
>>> +		vf->vring[i].irq = -EINVAL;
>>> +		ifcvf_set_vq_vector(vf, i, vector);
>>> +	}
>>> +
>>> +	vf->config_irq = irq;
>>> +	ifcvf_set_config_vector(vf, vector);
>>> +
>>> +	return 0;
>>> +
>>> +}
>>> +
>>> +static int ifcvf_request_vq_irq(struct ifcvf_adapter *adapter)
>>> +{
>>> +	struct ifcvf_hw *vf = &adapter->vf;
>>> +	int ret;
>>> +
>>> +	if (vf->msix_vector_status == MSIX_VECTOR_PER_VQ_AND_CONFIG)
>>> +		ret = ifcvf_request_per_vq_irq(adapter);
>>> +	else
>>> +		ret = ifcvf_request_shared_vq_irq(adapter);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static int ifcvf_request_config_irq(struct ifcvf_adapter *adapter)
>>> +{
>>> +	struct pci_dev *pdev = adapter->pdev;
>>> +	struct ifcvf_hw *vf = &adapter->vf;
>>> +	int config_vector, ret;
>>> +
>>> +	if (vf->msix_vector_status == MSIX_VECTOR_DEV_SHARED)
>>> +		return 0;
>>> +
>>> +	if (vf->msix_vector_status == MSIX_VECTOR_PER_VQ_AND_CONFIG)
>>> +		/* vector 0 ~ vf->nr_vring for vqs, num vf->nr_vring vector for config interrupt */
>>> +		config_vector = vf->nr_vring;
>>> +
>>> +	if (vf->msix_vector_status ==  MSIX_VECTOR_SHARED_VQ_AND_CONFIG)
>>> +		/* vector 0 for vqs and 1 for config interrupt */
>>> +		config_vector = 1;
>>> +
>>>    	snprintf(vf->config_msix_name, 256, "ifcvf[%s]-config\n",
>>>    		 pci_name(pdev));
>>> -	vector = 0;
>>> -	vf->config_irq = pci_irq_vector(pdev, vector);
>>> +	vf->config_irq = pci_irq_vector(pdev, config_vector);
>>>    	ret = devm_request_irq(&pdev->dev, vf->config_irq,
>>>    			       ifcvf_config_changed, 0,
>>>    			       vf->config_msix_name, vf);
>>>    	if (ret) {
>>>    		IFCVF_ERR(pdev, "Failed to request config irq\n");
>>> +		ifcvf_free_vq_irq(adapter, vf->nr_vring);
>>>    		return ret;
>>>    	}
>>> -	for (i = 0; i < vf->nr_vring; i++) {
>>> -		snprintf(vf->vring[i].msix_name, 256, "ifcvf[%s]-%d\n",
>>> -			 pci_name(pdev), i);
>>> -		vector = i + IFCVF_MSI_QUEUE_OFF;
>>> -		irq = pci_irq_vector(pdev, vector);
>>> -		ret = devm_request_irq(&pdev->dev, irq,
>>> -				       ifcvf_intr_handler, 0,
>>> -				       vf->vring[i].msix_name,
>>> -				       &vf->vring[i]);
>>> -		if (ret) {
>>> -			IFCVF_ERR(pdev,
>>> -				  "Failed to request irq for vq %d\n", i);
>>> -			ifcvf_free_irq(adapter, i);
>>> +	ifcvf_set_config_vector(vf, config_vector);
>>> -			return ret;
>>> -		}
>>> +	return 0;
>>> +}
>>> +
>>> +static int ifcvf_request_irq(struct ifcvf_adapter *adapter)
>>> +{
>>
>> As replied above, I think having two modes should be sufficient and the code
>> could be greatly simplified.
>>
>> Thanks
>>
> Well it is claimed there are platforms where we are short
> on vectors. 3 versus 2 seems a 50% saving. You disagree?
>
>>> +	struct ifcvf_hw *vf = &adapter->vf;
>>> +	int nvectors, ret, max_intr;
>>> -		vf->vring[i].irq = irq;
>>> +	nvectors = ifcvf_alloc_vectors(adapter);
>>> +	if (!(nvectors > 0))
>>> +		return nvectors;
>>> +
>>> +	vf->msix_vector_status = MSIX_VECTOR_PER_VQ_AND_CONFIG;
>>> +	max_intr = vf->nr_vring + 1;
>>> +	if (nvectors < max_intr)
>>> +		vf->msix_vector_status = MSIX_VECTOR_SHARED_VQ_AND_CONFIG;
>>> +
>>> +	if (nvectors == 1) {
>>> +		vf->msix_vector_status = MSIX_VECTOR_DEV_SHARED;
>>> +		ret = ifcvf_request_dev_shared_irq(adapter);
>>> +
>>> +		return ret;
>>>    	}
>>> +	ret = ifcvf_request_vq_irq(adapter);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	ret = ifcvf_request_config_irq(adapter);
>>> +
>>> +	if (ret)
>>> +		return ret;
>>> +
>>>    	return 0;
>>>    }
>>> @@ -441,7 +611,10 @@ static int ifcvf_vdpa_get_vq_irq(struct vdpa_device *vdpa_dev,
>>>    {
>>>    	struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>>> -	return vf->vring[qid].irq;
>>> +	if (vf->vqs_shared_irq < 0)
>>> +		return vf->vring[qid].irq;
>>> +	else
>>> +		return -EINVAL;
>>>    }
>>>    static struct vdpa_notification_area ifcvf_get_vq_notification(struct vdpa_device *vdpa_dev,

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