Re: [PATCH v2] xen/pci: Refactor PCI MSI interrupts related code

[Jan Beulich <jbeulich@xxxxxxxx>]

On 21.04.2021 10:16, Roger Pau Monné wrote:
> On Wed, Apr 21, 2021 at 08:07:08AM +0000, Rahul Singh wrote:
>> Hi Jan,
>>
>>> On 20 Apr 2021, at 4:36 pm, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>
>>> On 20.04.2021 15:45, Rahul Singh wrote:
>>>>> On 19 Apr 2021, at 1:33 pm, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>>> On 19.04.2021 13:54, Julien Grall wrote:
>>>>>> For the time being, I think move this code in x86 is a lot better than 
>>>>>> #ifdef or keep the code in common code.
>>>>>
>>>>> Well, I would perhaps agree if it ended up being #ifdef CONFIG_X86.
>>>>> I would perhaps not agree if there was a new CONFIG_* which other
>>>>> (future) arch-es could select if desired.
>>>>
>>>> I agree with Julien moving the code to x86 file as currently it is 
>>>> referenced only in x86 code
>>>> and as of now we are not sure how other architecture will implement the 
>>>> Interrupt remapping
>>>> (via IOMMU or any other means).  
>>>>
>>>> Let me know if you are ok with moving the code to x86.
>>>
>>> I can't answer this with "yes" or "no" without knowing what the alternative
>>> would be. As said, if the alternative is CONFIG_X86 #ifdef-ary, then yes.
>>> If a separate CONFIG_* gets introduced (and selected by X86), then a
>>> separate file (getting built only when that new setting is y) would seem
>>> better to me.
>>
>> I just made a quick patch. Please let me know if below patch is ok. I move 
>> the definition to  "passthrough/x86/iommu.c” file.
>>
>> diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
>> index 705137f8be..199ce08612 100644
>> --- a/xen/drivers/passthrough/pci.c
>> +++ b/xen/drivers/passthrough/pci.c
>> @@ -1303,13 +1303,6 @@ static int __init setup_dump_pcidevs(void)
>>  }
>>  __initcall(setup_dump_pcidevs);
>>  
>> -int iommu_update_ire_from_msi(
>> -    struct msi_desc *msi_desc, struct msi_msg *msg)
>> -{
>> -    return iommu_intremap
>> -           ? iommu_call(&iommu_ops, update_ire_from_msi, msi_desc, msg) : 0;
>> -}
>> -
>>  static int iommu_add_device(struct pci_dev *pdev)
>>  {
>>      const struct domain_iommu *hd;
>> diff --git a/xen/drivers/passthrough/x86/iommu.c 
>> b/xen/drivers/passthrough/x86/iommu.c
>> index b90bb31bfe..cf51dec564 100644
>> --- a/xen/drivers/passthrough/x86/iommu.c
>> +++ b/xen/drivers/passthrough/x86/iommu.c
>> @@ -340,6 +340,13 @@ bool arch_iommu_use_permitted(const struct domain *d)
>>              likely(!p2m_get_hostp2m(d)->global_logdirty));
>>  }
>>  
>> +int iommu_update_ire_from_msi(
>> +    struct msi_desc *msi_desc, struct msi_msg *msg)
>> +{
>> +    return iommu_intremap
>> +           ? iommu_call(&iommu_ops, update_ire_from_msi, msi_desc, msg) : 0;
>> +}
>> +
>>  /*
>>   * Local variables:
>>   * mode: C
>> diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
>> index ea0cd0f1a2..bd42d87b72 100644
>> --- a/xen/include/xen/iommu.h
>> +++ b/xen/include/xen/iommu.h
>> @@ -243,7 +243,6 @@ struct iommu_ops {
>>                             u8 devfn, device_t *dev);
>>  #ifdef CONFIG_HAS_PCI
>>      int (*get_device_group_id)(u16 seg, u8 bus, u8 devfn);
>> -    int (*update_ire_from_msi)(struct msi_desc *msi_desc, struct msi_msg 
>> *msg);
>>  #endif /* HAS_PCI */
>>  
>>      void (*teardown)(struct domain *d);
>> @@ -272,6 +271,7 @@ struct iommu_ops {
>>      int (*adjust_irq_affinities)(void);
>>      void (*sync_cache)(const void *addr, unsigned int size);
>>      void (*clear_root_pgtable)(struct domain *d);
>> +    int (*update_ire_from_msi)(struct msi_desc *msi_desc, struct msi_msg 
>> *msg);
> 
> You also need to move the function prototype
> (iommu_update_ire_from_msi) from iommu.h into asm-x86/iommu.h,

The prototype can, in principle at least, remain where it is.

> or maybe you could just define the function itself as static inline in
> asm-x86/iommu.h?

Possibly (and in that case it would perhaps indeed be better to
move it there, compared to needing another #ifdef).

Jan