linux-kernel - Re: [PATCH v13 11/15] vfio/type1: Handle unmap/unpin and replay for VFIO_IOVA

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Date:   Thu, 6 Oct 2016 14:19:18 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, christoffer.dall@...aro.org,
        marc.zyngier@....com, robin.murphy@....com, will.deacon@....com,
        joro@...tes.org, tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        drjones@...hat.com, linux-kernel@...r.kernel.org,
        Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
        p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
        Jean-Philippe.Brucker@....com, yehuday@...vell.com,
        Manish.Jaggi@...iumnetworks.com
Subject: Re: [PATCH v13 11/15] vfio/type1: Handle unmap/unpin and replay for
 VFIO_IOVA_RESERVED slots

On Thu,  6 Oct 2016 08:45:27 +0000
Eric Auger <eric.auger@...hat.com> wrote:

> Before allowing the end-user to create VFIO_IOVA_RESERVED dma slots,
> let's implement the expected behavior for removal and replay.
> 
> As opposed to user dma slots, reserved IOVAs are not systematically bound
> to PAs and PAs are not pinned. VFIO just initializes the IOVA "aperture".
> IOVAs are allocated outside of the VFIO framework, by the MSI layer which
> is responsible to free and unmap them. The MSI mapping resources are freeed

nit, extra 'e', "freed"

> by the IOMMU driver on domain destruction.
> 
> On the creation of a new domain, the "replay" of a reserved slot simply
> needs to set the MSI aperture on the new domain.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> 
> ---
> v12 -> v13:
> - use dma-iommu iommu_get_dma_msi_region_cookie
> 
> v9 -> v10:
> - replay of a reserved slot sets the MSI aperture on the new domain
> - use VFIO_IOVA_RESERVED_MSI enum value instead of VFIO_IOVA_RESERVED
> 
> v7 -> v8:
> - do no destroy anything anymore, just bypass unmap/unpin and iommu_map
>   on replay
> ---
>  drivers/vfio/Kconfig            |  1 +
>  drivers/vfio/vfio_iommu_type1.c | 10 +++++++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
> index da6e2ce..673ec79 100644
> --- a/drivers/vfio/Kconfig
> +++ b/drivers/vfio/Kconfig
> @@ -1,6 +1,7 @@
>  config VFIO_IOMMU_TYPE1
>  	tristate
>  	depends on VFIO
> +	select IOMMU_DMA
>  	default n
>  
>  config VFIO_IOMMU_SPAPR_TCE
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 65a4038..5bc5fc9 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -36,6 +36,7 @@
>  #include <linux/uaccess.h>
>  #include <linux/vfio.h>
>  #include <linux/workqueue.h>
> +#include <linux/dma-iommu.h>
>  
>  #define DRIVER_VERSION  "0.2"
>  #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@...hat.com>"
> @@ -387,7 +388,7 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
>  	struct vfio_domain *domain, *d;
>  	long unlocked = 0;
>  
> -	if (!dma->size)
> +	if (!dma->size || dma->type != VFIO_IOVA_USER)
>  		return;
>  	/*
>  	 * We use the IOMMU to track the physical addresses, otherwise we'd
> @@ -724,6 +725,13 @@ static int vfio_iommu_replay(struct vfio_iommu *iommu,
>  		dma = rb_entry(n, struct vfio_dma, node);
>  		iova = dma->iova;
>  
> +		if (dma->type == VFIO_IOVA_RESERVED_MSI) {
> +			ret = iommu_get_dma_msi_region_cookie(domain->domain,
> +						     dma->iova, dma->size);
> +			WARN_ON(ret);
> +			continue;
> +		}

Why is this a passable error?  We consider an iommu_map() error on any
entry a failure.

> +
>  		while (iova < dma->iova + dma->size) {
>  			phys_addr_t phys = iommu_iova_to_phys(d->domain, iova);
>  			size_t size;