Re: [PATCH v7 6/8] irqchip/gicv2m: implement msi_doorbell_info callback

[Eric Auger]

Marc,
On 04/20/2016 11:27 AM, Marc Zyngier wrote:
> On 19/04/16 18:13, Eric Auger wrote:
>> This patch implements the msi_doorbell_info callback in the
>> gicv2m driver.
>>
>> The driver now is able to return its doorbell characteristics
>> (base, size, prot). A single doorbell is exposed.
>>
>> This will allow the msi layer to iommu_map this doorbell when
>> requested.
>>
>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>>
>> ---
>>
>> v7: creation
>> ---
>>  drivers/irqchip/irq-gic-v2m.c | 32 +++++++++++++++++++++++++++++++-
>>  1 file changed, 31 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c
>> index 28f047c..54690b9 100644
>> --- a/drivers/irqchip/irq-gic-v2m.c
>> +++ b/drivers/irqchip/irq-gic-v2m.c
>> @@ -24,6 +24,8 @@
>>  #include <linux/of_pci.h>
>>  #include <linux/slab.h>
>>  #include <linux/spinlock.h>
>> +#include <linux/percpu.h>
>> +#include <linux/iommu.h>
>>  
>>  /*
>>  * MSI_TYPER:
>> @@ -64,6 +66,7 @@ struct v2m_data {
>>  	u32 nr_spis;		/* The number of SPIs for MSIs */
>>  	unsigned long *bm;	/* MSI vector bitmap */
>>  	u32 flags;		/* v2m flags for specific implementation */
>> +	struct irq_chip_msi_doorbell_info doorbell_info;
>>  };
>>  
>>  static void gicv2m_mask_msi_irq(struct irq_data *d)
>> @@ -105,6 +108,16 @@ static void gicv2m_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
>>  		msg->data -= v2m->spi_start;
>>  }
>>  
>> +static const struct irq_chip_msi_doorbell_info *
>> +gicv2m_msi_doorbell_info(struct irq_data *data)
>> +{
>> +	struct v2m_data *v2m = irq_data_get_irq_chip_data(data);
>> +
>> +	if (!v2m)
>> +		return NULL;
> 
> How can this ever be NULL? I think you can drop that test.
OK
> 
>> +	return (const struct irq_chip_msi_doorbell_info *)(&v2m->doorbell_info);
> 
> Please don't do that. Use "const" in the functions that are using
> irq_chip_msi_doorbell_info, but do not make this "const" here.
It definitively compiles without casting so obviously this is not needed
but is there any other wrong thing I don't see?
we still want this function to return a pointer to a const?
> 
>> +}
>> +
>>  static struct irq_chip gicv2m_irq_chip = {
>>  	.name			= "GICv2m",
>>  	.irq_mask		= irq_chip_mask_parent,
>> @@ -112,6 +125,7 @@ static struct irq_chip gicv2m_irq_chip = {
>>  	.irq_eoi		= irq_chip_eoi_parent,
>>  	.irq_set_affinity	= irq_chip_set_affinity_parent,
>>  	.irq_compose_msi_msg	= gicv2m_compose_msi_msg,
>> +	.msi_doorbell_info	= gicv2m_msi_doorbell_info,
>>  };
>>  
>>  static int gicv2m_irq_gic_domain_alloc(struct irq_domain *domain,
>> @@ -247,6 +261,7 @@ static void gicv2m_teardown(void)
>>  
>>  	list_for_each_entry_safe(v2m, tmp, &v2m_nodes, entry) {
>>  		list_del(&v2m->entry);
>> +		free_percpu(v2m->doorbell_info.percpu_doorbells);
>>  		kfree(v2m->bm);
>>  		iounmap(v2m->base);
>>  		of_node_put(to_of_node(v2m->fwnode));
>> @@ -299,6 +314,7 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
>>  {
>>  	int ret;
>>  	struct v2m_data *v2m;
>> +	struct irq_chip_msi_doorbell __percpu *doorbell;
>>  
>>  	v2m = kzalloc(sizeof(struct v2m_data), GFP_KERNEL);
>>  	if (!v2m) {
>> @@ -311,11 +327,23 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
>>  
>>  	memcpy(&v2m->res, res, sizeof(struct resource));
>>  
>> +	v2m->doorbell_info.percpu_doorbells =
>> +		alloc_percpu(struct irq_chip_msi_doorbell);
>> +	if (WARN_ON(!v2m->doorbell_info.percpu_doorbells)) {
>> +		ret = -ENOMEM;
>> +		goto err_free_v2m;
>> +	}
>> +	doorbell = per_cpu_ptr(v2m->doorbell_info.percpu_doorbells, 0);
>> +	doorbell->base = v2m->res.start;
>> +	doorbell->size = 4;
>> +	doorbell->prot = IOMMU_WRITE;
> 
> You probably need to also have something that says IOMMU_DEVICE or
> something similar, because I'm afraid you're getting a memory mapping
> here. I've had a quick look at the two other series, but couldn't find
> anything that would force the memory attributes.
Yes you're right I currently just enforce the direction (which is
checked against what VFIO user registered). Do you refer to IOMMU_MMIO,
latterly proposed on the ML. In the positive, yes I intend to add it
once it gets upstreamed.

Thanks

Eric
> 
>> +	v2m->doorbell_info.nb_doorbells = 1;
>> +
>>  	v2m->base = ioremap(v2m->res.start, resource_size(&v2m->res));
>>  	if (!v2m->base) {
>>  		pr_err("Failed to map GICv2m resource\n");
>>  		ret = -ENOMEM;
>> -		goto err_free_v2m;
>> +		goto err_free_v2m_doorbells;
>>  	}
>>  
>>  	if (spi_start && nr_spis) {
>> @@ -359,6 +387,8 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
>>  
>>  err_iounmap:
>>  	iounmap(v2m->base);
>> +err_free_v2m_doorbells:
>> +	free_percpu(v2m->doorbell_info.percpu_doorbells);
>>  err_free_v2m:
>>  	kfree(v2m);
>>  	return ret;
>>
> 
> Thanks,
> 
> 	M.
>