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Subject[PATCH kernel v6 26/29] vfio: powerpc/spapr: Define v2 IOMMU
Date
The existing IOMMU requires VFIO_IOMMU_ENABLE call to enable actual use
of the container (i.e. call DMA map/unmap) and this is where we check
the rlimit for locked pages. It assumes that only as much memory
as a default DMA window can be mapped. Every DMA map/unmap request will
do pinning/unpinning of physical pages.

New IOMMU will split physical pages pinning and TCE table update.
It will require guest pages to be registered first and consequent
map/unmap requests to work only with pre-registered memory.
For the default single window case this means that the entire guest
(instead of 2GB) needs to be pinned before using VFIO.
However when a huge DMA window is added, no additional pinning will be
required, otherwise it would be guest RAM + 2GB.

This advertises v2 SPAPR TCE IOMMU and restricts what the userspace
can do with v1 or v2 IOMMUs.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v6:
* enforced limitations imposed by the SPAPR TCE IOMMU version
---
drivers/vfio/vfio_iommu_spapr_tce.c | 18 +++++++++++++++++-
include/uapi/linux/vfio.h | 2 ++
2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 9d240b4..e191438 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -95,6 +95,7 @@ struct tce_container {
bool enabled;
unsigned long locked_pages;
struct list_head mem_list;
+ bool v2;
};

struct tce_memory {
@@ -398,7 +399,7 @@ static void *tce_iommu_open(unsigned long arg)
{
struct tce_container *container;

- if (arg != VFIO_SPAPR_TCE_IOMMU) {
+ if ((arg != VFIO_SPAPR_TCE_IOMMU) && (arg != VFIO_SPAPR_TCE_v2_IOMMU)) {
pr_err("tce_vfio: Wrong IOMMU type\n");
return ERR_PTR(-EINVAL);
}
@@ -410,6 +411,8 @@ static void *tce_iommu_open(unsigned long arg)
mutex_init(&container->lock);
INIT_LIST_HEAD_RCU(&container->mem_list);

+ container->v2 = arg == VFIO_SPAPR_TCE_v2_IOMMU;
+
return container;
}

@@ -580,6 +583,7 @@ static long tce_iommu_ioctl(void *iommu_data,
case VFIO_CHECK_EXTENSION:
switch (arg) {
case VFIO_SPAPR_TCE_IOMMU:
+ case VFIO_SPAPR_TCE_v2_IOMMU:
ret = 1;
break;
default:
@@ -719,6 +723,9 @@ static long tce_iommu_ioctl(void *iommu_data,
case VFIO_IOMMU_SPAPR_REGISTER_MEMORY: {
struct vfio_iommu_spapr_register_memory param;

+ if (!container->v2)
+ return -EPERM;
+
minsz = offsetofend(struct vfio_iommu_spapr_register_memory,
size);

@@ -741,6 +748,9 @@ static long tce_iommu_ioctl(void *iommu_data,
case VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY: {
struct vfio_iommu_spapr_register_memory param;

+ if (!container->v2)
+ return -EPERM;
+
minsz = offsetofend(struct vfio_iommu_spapr_register_memory,
size);

@@ -761,6 +771,9 @@ static long tce_iommu_ioctl(void *iommu_data,
return 0;
}
case VFIO_IOMMU_ENABLE:
+ if (container->v2)
+ return -EPERM;
+
mutex_lock(&container->lock);
ret = tce_iommu_enable(container);
mutex_unlock(&container->lock);
@@ -768,6 +781,9 @@ static long tce_iommu_ioctl(void *iommu_data,


case VFIO_IOMMU_DISABLE:
+ if (container->v2)
+ return -EPERM;
+
mutex_lock(&container->lock);
tce_iommu_disable(container);
mutex_unlock(&container->lock);
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index b17e120..fbc5286 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -36,6 +36,8 @@
/* Two-stage IOMMU */
#define VFIO_TYPE1_NESTING_IOMMU 6 /* Implies v2 */

+#define VFIO_SPAPR_TCE_v2_IOMMU 7
+
/*
* The IOCTL interface is designed for extensibility by embedding the
* structure length (argsz) and flags into structures passed between
--
2.0.0


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