Re: [PATCH] vfio/iommu_type1: report the IOMMU aperture info
From: Pierre Morel
Date: Thu Nov 30 2017 - 10:11:51 EST
On 30/11/2017 15:08, Alex Williamson wrote:
On Thu, 30 Nov 2017 12:34:38 +0100
Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx> 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 <pmorel@xxxxxxxxxxxxxxxxxx>
---
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 BÃblingen - Germany