[PATCH v8 04/16] MSI-X: update GSI routing after changed MSI-X configuration

[Marc Zyngier]

On 04/11/16 17:31, Andre Przywara wrote:
> When we set up GSI routing to map MSIs to KVM's GSI numbers, we
> write the current device's MSI setup into the kernel routing table.
> However the device driver in the guest can use PCI configuration space
> accesses to change the MSI configuration (address and/or payload data).
> Whenever this happens after we have setup the routing table already,
> we must amend the previously sent data.
> So when MSI-X PCI config space accesses write address or payload,
> find the associated GSI number and the matching routing table entry
> and update the kernel routing table (only if the data has changed).
> 
> This fixes vhost-net, where the queue's IRQFD was setup before the
> MSI vectors.
> 
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> ---
>  include/kvm/irq.h |  1 +
>  irq.c             | 31 +++++++++++++++++++++++++++++++
>  virtio/pci.c      | 36 +++++++++++++++++++++++++++++++++---
>  3 files changed, 65 insertions(+), 3 deletions(-)
> 
> diff --git a/include/kvm/irq.h b/include/kvm/irq.h
> index bb71521..f35eb7e 100644
> --- a/include/kvm/irq.h
> +++ b/include/kvm/irq.h
> @@ -21,5 +21,6 @@ int irq__exit(struct kvm *kvm);
>  
>  int irq__allocate_routing_entry(void);
>  int irq__add_msix_route(struct kvm *kvm, struct msi_msg *msg);
> +void irq__update_msix_route(struct kvm *kvm, u32 gsi, struct msi_msg *msg);
>  
>  #endif
> diff --git a/irq.c b/irq.c
> index a742aa2..895e5eb 100644
> --- a/irq.c
> +++ b/irq.c
> @@ -93,6 +93,37 @@ int irq__add_msix_route(struct kvm *kvm, struct msi_msg *msg)
>  	return next_gsi++;
>  }
>  
> +static bool update_data(u32 *ptr, u32 newdata)
> +{
> +	if (*ptr == newdata)
> +		return false;
> +
> +	*ptr = newdata;
> +	return true;
> +}
> +
> +void irq__update_msix_route(struct kvm *kvm, u32 gsi, struct msi_msg *msg)
> +{
> +	struct kvm_irq_routing_msi *entry;
> +	unsigned int i;
> +	bool changed;
> +
> +	for (i = 0; i < irq_routing->nr; i++)
> +		if (gsi == irq_routing->entries[i].gsi)
> +			break;
> +	if (i == irq_routing->nr)
> +		return;
> +
> +	entry = &irq_routing->entries[i].u.msi;
> +
> +	changed  = update_data(&entry->address_hi, msg->address_hi);
> +	changed |= update_data(&entry->address_lo, msg->address_lo);
> +	changed |= update_data(&entry->data, msg->data);
> +
> +	if (changed)
> +		ioctl(kvm->vm_fd, KVM_SET_GSI_ROUTING, irq_routing);

Check the return value and let the caller know if something has failed?

> +}
> +
>  int __attribute__((weak)) irq__exit(struct kvm *kvm)
>  {
>  	free(irq_routing);
> diff --git a/virtio/pci.c b/virtio/pci.c
> index 072e5b7..b3b4aac 100644
> --- a/virtio/pci.c
> +++ b/virtio/pci.c
> @@ -152,6 +152,30 @@ static bool virtio_pci__io_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 p
>  	return ret;
>  }
>  
> +static void update_msix_map(struct virtio_pci *vpci,
> +			    struct msix_table *msix_entry, u32 vecnum)
> +{
> +	u32 gsi, i;
> +
> +	/* Find the GSI number used for that vector */
> +	if (vecnum == vpci->config_vector) {
> +		gsi = vpci->config_gsi;
> +	} else {
> +		for (i = 0; i < VIRTIO_PCI_MAX_VQ; i++)
> +			if (vpci->vq_vector[i] == vecnum)
> +				break;
> +		if (i == VIRTIO_PCI_MAX_VQ)
> +			return;
> +		gsi = vpci->gsis[i];
> +	}
> +
> +	if (gsi == 0)
> +		return;
> +
> +	msix_entry = &msix_entry[vecnum];
> +	irq__update_msix_route(vpci->kvm, gsi, &msix_entry->msg);
> +}
> +
>  static bool virtio_pci__specific_io_out(struct kvm *kvm, struct virtio_device *vdev, u16 port,
>  					void *data, int size, int offset)
>  {
> @@ -270,10 +294,16 @@ static void virtio_pci__msix_mmio_callback(struct kvm_cpu *vcpu,
>  		offset	= vpci->msix_io_block;
>  	}
>  
> -	if (is_write)
> -		memcpy(table + addr - offset, data, len);
> -	else
> +	if (!is_write) {
>  		memcpy(data, table + addr - offset, len);
> +		return;
> +	}
> +
> +	memcpy(table + addr - offset, data, len);
> +
> +	/* Did we just update the address or payload? */
> +	if (addr % 0x10 < 0xc)
> +		update_msix_map(vpci, table, (addr - offset) / 16);

Where are these constants coming from? Please stick to either decimal or
hex...

>  }
>  
>  static void virtio_pci__signal_msi(struct kvm *kvm, struct virtio_pci *vpci, int vec)
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...