linux-kernel - Re: [PATCH 2/2] vfio: type1: conditionally check MSI remapping at irq domain level

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Message-ID: <4304c447-0523-08a0-3327-e974bedc3c73@suse.com>
Date:   Thu, 2 Mar 2017 13:38:19 +0100
From:   Mian Yousaf Kaukab <yousaf.kaukab@...e.com>
To:     Auger Eric <eric.auger@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, marc.zyngier@....com,
        alex.williamson@...hat.com
Cc:     will.deacon@....com
Subject: Re: [PATCH 2/2] vfio: type1: conditionally check MSI remapping at irq
 domain level

On 03/02/2017 11:24 AM, Auger Eric wrote:
> Hi,
> 
> On 02/03/2017 11:01, Mian Yousaf Kaukab wrote:
>> Check only if irq domains are available.
>>
>> Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@...e.com>
>> ---
>>   drivers/vfio/vfio_iommu_type1.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index bd6f293c4ebd..e3ed50e40ead 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -1287,8 +1287,9 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>>   	INIT_LIST_HEAD(&domain->group_list);
>>   	list_add(&group->next, &domain->group_list);
>>   
>> -	msi_remap = resv_msi ? irq_domain_check_msi_remap() :
>> -				iommu_capable(bus, IOMMU_CAP_INTR_REMAP);
>> +	msi_remap = resv_msi && IS_ENABLED(CONFIG_IRQ_DOMAIN) ?
>> +			irq_domain_check_msi_remap() :
>> +			iommu_capable(bus, IOMMU_CAP_INTR_REMAP);
> Is that patch actually needed after [PATCH 1/2] irqdomain: add empty
> irq_domain_check_msi_remap. irq_domain_check_msi_remap() should be
> defined and if you follow my suggestion, would return false. Anyway in
> your case resv_msi should be false.
I agree its an overkill if resv_msi is guaranteed to be false. What I am 
unsure about is that, if iommu have IOMMU_RESV_MSI regions that would 
mean that irq domains are selected in the build. If this is not 
guaranteed, then we need to add this check.

> 
> Thanks
> 
> Eric

BR,
Yousaf