linux-kernel - Re: [RFC v4 15/16] vfio/type1: Check MSI remapping at irq domain level

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Message-ID: <HE1PR04MB13219CC90CE2BBE62356D94CFF920@HE1PR04MB1321.eurprd04.prod.outlook.com>
Date:   Thu, 22 Dec 2016 12:41:53 +0000
From:   Diana Madalina Craciun <diana.craciun@....com>
To:     Eric Auger <eric.auger@...hat.com>,
        "eric.auger.pro@...il.com" <eric.auger.pro@...il.com>,
        "christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "will.deacon@....com" <will.deacon@....com>,
        "joro@...tes.org" <joro@...tes.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "jason@...edaemon.net" <jason@...edaemon.net>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "drjones@...hat.com" <drjones@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "pranav.sawargaonkar@...il.com" <pranav.sawargaonkar@...il.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "punit.agrawal@....com" <punit.agrawal@....com>,
        "gpkulkarni@...il.com" <gpkulkarni@...il.com>,
        "shankerd@...eaurora.org" <shankerd@...eaurora.org>,
        Bharat Bhushan <bharat.bhushan@....com>
Subject: Re: [RFC v4 15/16] vfio/type1: Check MSI remapping at irq domain
 level

Hi Eric,

On 12/13/2016 10:32 PM, Eric Auger wrote:
> In case the IOMMU does not bypass MSI transactions (typical
> case on ARM), we check all MSI controllers are IRQ remapping
> capable. If not the IRQ assignment may be unsafe.
>
> At this stage the arm-smmu-(v3) still advertise the
> IOMMU_CAP_INTR_REMAP capability at IOMMU level. This will be
> removed in subsequent patches.
>
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index d07fe73..a05648b 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -37,6 +37,7 @@
>  #include <linux/vfio.h>
>  #include <linux/workqueue.h>
>  #include <linux/dma-iommu.h>
> +#include <linux/irqdomain.h>
>  
>  #define DRIVER_VERSION  "0.2"
>  #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@...hat.com>"
> @@ -765,7 +766,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  	struct vfio_domain *domain, *d;
>  	struct bus_type *bus = NULL;
>  	int ret;
> -	bool resv_msi;
> +	bool resv_msi, msi_remap;
>  	phys_addr_t resv_msi_base;
>  
>  	mutex_lock(&iommu->lock);
> @@ -818,8 +819,10 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  	INIT_LIST_HEAD(&domain->group_list);
>  	list_add(&group->next, &domain->group_list);
>  
> -	if (!allow_unsafe_interrupts &&
> -	    !iommu_capable(bus, IOMMU_CAP_INTR_REMAP)) {
> +	msi_remap = resv_msi ? irq_domain_check_msi_remap() :
> +			       iommu_capable(bus, IOMMU_CAP_INTR_REMAP);
> +
> +	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",
>  		       __func__);
>  		ret = -EPERM;

I tested your v4.9-reserved-v4 branch on a ITS capable hardware (NXP
LS2080), so I did not set allow_unsafe_interrupts. It fails here
complaining that the there is no interrupt remapping support. The
irq_domain_check_msi_remap function returns false as none of the checked
domains has the IRQ_DOMAIN_FLAG_MSI_REMAP flag set. I think the reason
is that the flags are not propagated through the domain hierarchy when
the domain is created.

Thanks,

Diana