Re: [RFC v3 02/15] vfio: expose MSI mapping requirement through VFIO_IOMMU_GET_INFO

[Eric Auger]

Hi Marc,
On 02/18/2016 10:34 AM, Marc Zyngier wrote:
> On Fri, 12 Feb 2016 08:13:04 +0000
> Eric Auger <eric.auger@xxxxxxxxxx> wrote:
> 
>> This patch allows the user-space to retrieve whether msi write
>> transaction addresses must be mapped. This is returned through the
>> VFIO_IOMMU_GET_INFO API and its new flag: VFIO_IOMMU_INFO_REQUIRE_MSI_MAP.
>>
>> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@xxxxxxxxxxxxx>
>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>>
>> ---
>>
>> RFC v1 -> v1:
>> - derived from
>>   [RFC PATCH 3/6] vfio: Extend iommu-info to return MSIs automap state
>> - renamed allow_msi_reconfig into require_msi_mapping
>> - fixed VFIO_IOMMU_GET_INFO
>> ---
>>  drivers/vfio/vfio_iommu_type1.c | 26 ++++++++++++++++++++++++++
>>  include/uapi/linux/vfio.h       |  1 +
>>  2 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index 6f1ea3d..c5b57e1 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -255,6 +255,29 @@ static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)
>>  }
>>  
>>  /*
>> + * vfio_domains_require_msi_mapping: indicates whether MSI write transaction
>> + * addresses must be mapped
>> + *
>> + * returns true if it does
>> + */
>> +static bool vfio_domains_require_msi_mapping(struct vfio_iommu *iommu)
>> +{
>> +	struct vfio_domain *d;
>> +	bool ret;
>> +
>> +	mutex_lock(&iommu->lock);
>> +	/* All domains have same require_msi_map property, pick first */
>> +	d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
>> +	if (iommu_domain_get_attr(d->domain, DOMAIN_ATTR_MSI_MAPPING, NULL) < 0)
>> +		ret = false;
>> +	else
>> +		ret = true;
> 
> nit: this could be simplified as:
> 
> ret = (iommu_domain_get_attr(d->domain, DOMAIN_ATTR_MSI_MAPPING, NULL) == 0);
sure ;-)
> 
>> +	mutex_unlock(&iommu->lock);
>> +
>> +	return ret;
>> +}
>> +
>> +/*
>>   * Attempt to pin pages.  We really don't want to track all the pfns and
>>   * the iommu can only map chunks of consecutive pfns anyway, so get the
>>   * first page and all consecutive pages with the same locking.
>> @@ -997,6 +1020,9 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>>  
>>  		info.flags = VFIO_IOMMU_INFO_PGSIZES;
>>  
>> +		if (vfio_domains_require_msi_mapping(iommu))
>> +			info.flags |= VFIO_IOMMU_INFO_REQUIRE_MSI_MAP;
>> +
>>  		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
>>  
>>  		return copy_to_user((void __user *)arg, &info, minsz);
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> index 7d7a4c6..43e183b 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -400,6 +400,7 @@ struct vfio_iommu_type1_info {
>>  	__u32	argsz;
>>  	__u32	flags;
>>  #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)	/* supported page sizes info */
>> +#define VFIO_IOMMU_INFO_REQUIRE_MSI_MAP (1 << 1)/* MSI must be mapped */
>>  	__u64	iova_pgsizes;		/* Bitmap of supported page sizes */
>>  };
>>  
> 
> 
> FWIW:
> 
> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
thanks

Eric
> 
> 	M.
>