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

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Date:   Thu, 2 Mar 2017 11:24:39 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Mian Yousaf Kaukab <yousaf.kaukab@...e.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

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.

Thanks

Eric
>  
>  	if (!allow_unsafe_interrupts && !msi_remap) {
>  		pr_warn("%s: No interrupt remapping support.  Use the module param \"allow_unsafe_interrupts\" to enable VFIO IOMMU support on this platform\n",
>