On 30/11/2017 15:08, Alex Williamson wrote:
> On Thu, 30 Nov 2017 12:34:38 +0100
> Pierre Morel <[email protected]> wrote:
>
>> When userland VFIO defines a new IOMMU for a guest it may
>> want to specify to the guest the physical limits of
>> the underlying host IOMMU to avoid access to forbidden
>> memory ranges.
>>
>> Currently, the vfio_iommu_type1 driver does not report this
>> information to userland.
>>
>> Let's extend the vfio_iommu_type1_info structure reported
>> by the ioctl VFIO_IOMMU_GET_INFO command to report the
>> IOMMU limits as new uint64_t entries aperture_start and
>> aperture_end.
>>
>> Let's also extend the flags bit map to add a flag specifying
>> if this extension of the info structure is reported or not.
>>
>> Signed-off-by: Pierre Morel <[email protected]>
>> ---
>> drivers/vfio/vfio_iommu_type1.c | 42 +++++++++++++++++++++++++++++++++++++++++
>> include/uapi/linux/vfio.h | 3 +++
>> 2 files changed, 45 insertions(+)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index 8549cb1..7da5fe0 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -1526,6 +1526,40 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
>> return ret;
>> }
>>
>> +/**
>> + * vfio_get_aperture - report minimal aperture of a vfio_iommu
>> + * @iommu: the current vfio_iommu
>> + * @start: a pointer to the aperture start
>> + * @end : a pointer to the aperture end
>> + *
>> + * This function iterate on the domains using the given vfio_iommu
>> + * and restrict the aperture to the minimal aperture common
>> + * to all domains sharing this vfio_iommu.
>> + */
>> +static void vfio_get_aperture(struct vfio_iommu *iommu, uint64_t *start,
>> + uint64_t *end)
>> +{
>> + struct iommu_domain_geometry geometry;
>> + struct vfio_domain *domain;
>> +
>> + *start = 0;
>> + *end = U64_MAX;
>> +
>> + mutex_lock(&iommu->lock);
>> + /* loop on all domains using this vfio_iommu */
>> + list_for_each_entry(domain, &iommu->domain_list, next) {
>> + iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY,
>> + &geometry);
>> + if (geometry.force_aperture) {
>> + if (geometry.aperture_start > *start)
>> + *start = geometry.aperture_start;
>> + if (geometry.aperture_end < *end)
>> + *end = geometry.aperture_end;
>> + }
>> + }
>> + mutex_unlock(&iommu->lock);
>> +}
>> +
>> static long vfio_iommu_type1_ioctl(void *iommu_data,
>> unsigned int cmd, unsigned long arg)
>> {
>> @@ -1560,6 +1594,14 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>>
>> info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
>>
>> + minsz = min_t(size_t, info.argsz, sizeof(info));
>> + if (minsz >= offsetofend(struct vfio_iommu_type1_info,
>> + aperture_end)) {
>> + info.flags |= VFIO_IOMMU_INFO_APERTURE;
>> + vfio_get_aperture(iommu, &info.aperture_start,
>> + &info.aperture_end);
>> + }
>> +
>> return copy_to_user((void __user *)arg, &info, minsz) ?
>> -EFAULT : 0;
>>
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> index 0fb25fb..780d909 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -519,6 +519,9 @@ struct vfio_iommu_type1_info {
>> __u32 flags;
>> #define VFIO_IOMMU_INFO_PGSIZES (1 << 0) /* supported page sizes info */
>> __u64 iova_pgsizes; /* Bitmap of supported page sizes */
>> +#define VFIO_IOMMU_INFO_APERTURE (1 << 1) /* supported aperture info */
>> + __u64 aperture_start; /* start of DMA aperture */
>> + __u64 aperture_end; /* end of DMA aperture */
>> };
>>
>> #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
>
> This only supports the most simple topology, even x86 cannot claim to
> have a single contiguous aperture, it's typically bisected by an MSI
> window. I think we need an API that supports one or more apertures
> out of the box. Also as Eric indicates, a capability is probably the
> better option for creating a flexible structure. Thanks,
>
> Alex
>
Yes, I understand that a capability here is a must, I will follow this way.
For having multiple aperture and MSI protection, I understood it was
done using windows and reserved regions.
Can you point me to my error?
Thanks,
Pierre
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
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