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SubjectRe: [PATCH RFC v2 03/18] irq/dev-msi: Create IR-DEV-MSI irq domain
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Hi Dan,

On 7/21/2020 9:21 AM, Jason Gunthorpe wrote:
> On Tue, Jul 21, 2020 at 09:02:35AM -0700, Dave Jiang wrote:
>> From: Megha Dey <megha.dey@intel.com>
>>
>> When DEV_MSI is enabled, the dev_msi_default_domain is updated to the
>> base DEV-MSI irq domain. If interrupt remapping is enabled, we create
>> a new IR-DEV-MSI irq domain and update the dev_msi_default domain to
>> the same.
>>
>> For X86, introduce a new irq_alloc_type which will be used by the
>> interrupt remapping driver.
>
> Why? Shouldn't this by symmetrical with normal MSI? Does MSI do this?

Since I am introducing the new dev msi domain for the case when IR_REMAP
is turned on, I have introduced the new type in this patch.

MSI/MSIX have their own irq alloc types which are also only used by the
intel remapping driver..

>
> I would have thought you'd want to switch to this remapping mode as
> part of vfio or something like current cases.

Can you let me know what current case you are referring to?
>
>> +struct irq_domain *create_remap_dev_msi_irq_domain(struct irq_domain *parent,
>> + const char *name)
>> +{
>> + struct fwnode_handle *fn;
>> + struct irq_domain *domain;
>> +
>> + fn = irq_domain_alloc_named_fwnode(name);
>> + if (!fn)
>> + return NULL;
>> +
>> + domain = msi_create_irq_domain(fn, &dev_msi_ir_domain_info, parent);
>> + if (!domain) {
>> + pr_warn("failed to initialize irqdomain for IR-DEV-MSI.\n");
>> + return ERR_PTR(-ENXIO);
>> + }
>> +
>> + irq_domain_update_bus_token(domain, DOMAIN_BUS_PLATFORM_MSI);
>> +
>> + if (!dev_msi_default_domain)
>> + dev_msi_default_domain = domain;
>> +
>> + return domain;
>> +}
>
> What about this code creates a "remap" ? ie why is the function called
> "create_remap" ?

Well, this function creates a new domain for the case when IR_REMAP is
enabled, hence I called it create_remap...

>
>> diff --git a/include/linux/msi.h b/include/linux/msi.h
>> index 1da97f905720..7098ba566bcd 100644
>> +++ b/include/linux/msi.h
>> @@ -378,6 +378,9 @@ void *platform_msi_get_host_data(struct irq_domain *domain);
>> void platform_msi_write_msg(struct irq_data *data, struct msi_msg *msg);
>> void platform_msi_unmask_irq(struct irq_data *data);
>> void platform_msi_mask_irq(struct irq_data *data);
>> +
>> +int dev_msi_prepare(struct irq_domain *domain, struct device *dev,
>> + int nvec, msi_alloc_info_t *arg);
>
> I wonder if this should use the popular #ifdef dev_msi_prepare scheme
> instead of a weak symbol?

Ok, I will look into the #ifdef option.
>
> Jason
>

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