The vfio_iommu_spapr_tce driver advertises kernel's support for
v1 and v2 IOMMU support, however it is not always possible to use
the requested IOMMU type. For example, a pseries host platform does not
support dynamic DMA windows so v2 cannot initialize and QEMU fails to
start.

This adds a fallback to the v1 IOMMU if v2 cannot be used.

Fixes: 318f67ce1371 "vfio: spapr: Add DMA memory preregistering (SPAPR IOMMU v2)"
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v2:
* updated commit log

---
 hw/vfio/common.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 7b2924c..cd81cc9 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1040,6 +1040,11 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
             v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU;
         ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
         if (ret) {
+            container->iommu_type = VFIO_SPAPR_TCE_IOMMU;
+            v2 = false;
+            ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
+        }
+        if (ret) {
             error_setg_errno(errp, errno, "failed to set iommu for container");
             ret = -errno;
             goto free_container_exit;
-- 
2.11.0

On Tue, Dec 12, 2017 at 04:16:19PM +1100, Alexey Kardashevskiy wrote:
> The vfio_iommu_spapr_tce driver advertises kernel's support for
> v1 and v2 IOMMU support, however it is not always possible to use
> the requested IOMMU type. For example, a pseries host platform does not
> support dynamic DMA windows so v2 cannot initialize and QEMU fails to
> start.
> 
> This adds a fallback to the v1 IOMMU if v2 cannot be used.
> 
> Fixes: 318f67ce1371 "vfio: spapr: Add DMA memory preregistering (SPAPR IOMMU v2)"
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Alex, will you take this through your tree, or should I take it
through mine?

> ---
> Changes:
> v2:
> * updated commit log
> 
> ---
>  hw/vfio/common.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 7b2924c..cd81cc9 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1040,6 +1040,11 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>              v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU;
>          ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
>          if (ret) {
> +            container->iommu_type = VFIO_SPAPR_TCE_IOMMU;
> +            v2 = false;
> +            ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
> +        }
> +        if (ret) {
>              error_setg_errno(errp, errno, "failed to set iommu for container");
>              ret = -errno;
>              goto free_container_exit;

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

On 15/12/17 17:01, David Gibson wrote:
> On Tue, Dec 12, 2017 at 04:16:19PM +1100, Alexey Kardashevskiy wrote:
>> The vfio_iommu_spapr_tce driver advertises kernel's support for
>> v1 and v2 IOMMU support, however it is not always possible to use
>> the requested IOMMU type. For example, a pseries host platform does not
>> support dynamic DMA windows so v2 cannot initialize and QEMU fails to
>> start.
>>
>> This adds a fallback to the v1 IOMMU if v2 cannot be used.
>>
>> Fixes: 318f67ce1371 "vfio: spapr: Add DMA memory preregistering (SPAPR IOMMU v2)"
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> 
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> 
> Alex, will you take this through your tree, or should I take it
> through mine?


It is already in upstream.

> 
>> ---
>> Changes:
>> v2:
>> * updated commit log
>>
>> ---
>>  hw/vfio/common.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index 7b2924c..cd81cc9 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -1040,6 +1040,11 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>              v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU;
>>          ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
>>          if (ret) {
>> +            container->iommu_type = VFIO_SPAPR_TCE_IOMMU;
>> +            v2 = false;
>> +            ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
>> +        }
>> +        if (ret) {
>>              error_setg_errno(errp, errno, "failed to set iommu for container");
>>              ret = -errno;
>>              goto free_container_exit;
> 


-- 
Alexey