Up until f9f6b22ab "xen/arm: Map ITS doorbell register to IOMMU page
tables" the only caller of iommu_map on ARM was grant_table.c which has
a specific usage model and restrictions as described by the in-code
comment in arm_iommu_map_page.
f9f6b22ab introduced a second caller to iommu_map on ARM:
vgic_v3_its_init_virtual. This specific statement in the
f9f6b22ab commit message is wrong:
"Note that the 1:1 check in arm_iommu_map_page remains for now, as
virtual ITSes are currently only created for hwdom where the doorbell
mapping is always 1:1."
Leading to crashes any time the hardware domain is not direct-mapped
(e.g. cache coloring and non-Dom0 hardware domain):
(XEN) Xen BUG at drivers/passthrough/arm/iommu_helpers.c:49
[...]
(XEN) Xen call trace:
(XEN) [<00000a000024c758>] arm_iommu_map_page+0x80/0x90 (PC)
(XEN) [<00000a000024c750>] arm_iommu_map_page+0x78/0x90 (LR)
(XEN) [<00000a0000250884>] iommu_map+0xcc/0x29c
(XEN) [<00000a0000288024>] vgic_v3_its_init_domain+0x18c/0x1e8
(XEN) [<00000a0000285228>] vgic-v3.c#vgic_v3_domain_init+0x168/0x21c
(XEN) [<00000a0000281dcc>] domain_vgic_init+0x14c/0x210
(XEN) [<00000a00002705a4>] arch_domain_create+0x150/0x1f0
(XEN) [<00000a00002055e8>] domain_create+0x47c/0x6c0
(XEN) [<00000a00002cf090>] create_domUs+0x7f8/0x8cc
(XEN) [<00000a00002eb588>] start_xen+0x8f4/0x998
(XEN) [<00000a000020018c>] head.o#primary_switched+0x4/0x10
Specifically, non-1:1 hardware domain exists with cache coloring
enabled. For that, is_domain_direct_mapped(d) is false but
domain_use_host_layout(d) is true.
At a minimum, we need to change the is_domain_direct_mapped(d) check in
arm_iommu_map_page into a domain_use_host_layout(d) check. But in
preparation of exposing vITS to domUs, let's take this opportunity to
generalize the arm_iommu_map_page function further to be more generic
and unopinionated. Move the in-code comment specific to the grant table
can live in grant-table.c instead.
Signed-off-by: Stefano Stabellini <stefano.stabell...@amd.com>
---
xen/common/grant_table.c | 10 ++++++++--
xen/drivers/passthrough/arm/iommu_helpers.c | 13 +------------
2 files changed, 9 insertions(+), 14 deletions(-)
diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index cf131c43a1..2e08dac656 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -1274,8 +1274,14 @@ map_grant_ref(
}
/*
- * We're not translated, so we know that dfns and mfns are
- * the same things, so the IOMMU entry is always 1-to-1.
+ * Grant mappings can be used for DMA requests. The dev_bus_addr
+ * returned by the hypercall is the MFN (not the IPA). For
+ * device protected by an IOMMU, Xen needs to add a 1:1 mapping
+ * in the domain p2m to allow DMA request to work. This is only
+ * valid when the domain is directed mapped.
+ *
+ * We're not translated, so we know that dfns and mfns are the
+ * same things, so the IOMMU entry is always 1-to-1.
*/
if ( !(op->flags & GNTMAP_readonly) && node.cnt.wr == 1 )
kind = IOMMUF_readable | IOMMUF_writable;
diff --git a/xen/drivers/passthrough/arm/iommu_helpers.c
b/xen/drivers/passthrough/arm/iommu_helpers.c
index 5cb1987481..dae5fc0caa 100644
--- a/xen/drivers/passthrough/arm/iommu_helpers.c
+++ b/xen/drivers/passthrough/arm/iommu_helpers.c
@@ -36,17 +36,6 @@ int __must_check arm_iommu_map_page(struct domain *d, dfn_t
dfn, mfn_t mfn,
{
p2m_type_t t;
- /*
- * Grant mappings can be used for DMA requests. The dev_bus_addr
- * returned by the hypercall is the MFN (not the IPA). For device
- * protected by an IOMMU, Xen needs to add a 1:1 mapping in the domain
- * p2m to allow DMA request to work.
- * This is only valid when the domain is directed mapped. Hence this
- * function should only be used by gnttab code with gfn == mfn == dfn.
- */
- BUG_ON(!is_domain_direct_mapped(d));
- BUG_ON(mfn_x(mfn) != dfn_x(dfn));
-
/* We only support readable and writable flags */
if ( !(flags & (IOMMUF_readable | IOMMUF_writable)) )
return -EINVAL;
@@ -57,7 +46,7 @@ int __must_check arm_iommu_map_page(struct domain *d, dfn_t
dfn, mfn_t mfn,
* The function guest_physmap_add_entry replaces the current mapping
* if there is already one...
*/
- return guest_physmap_add_entry(d, _gfn(dfn_x(dfn)), _mfn(dfn_x(dfn)),
+ return guest_physmap_add_entry(d, _gfn(dfn_x(dfn)), mfn,
IOMMUF_order(flags), t);
}
--
2.25.1
