[PATCH v6 9/9] xen/arm: Map ITS doorbell register to IOMMU page tables

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

From: Rahul Singh <rahul.singh@xxxxxxx>

When ITS is enabled and PCI devices that are behind an SMMU generate an
MSI interrupt, SMMU fault will be observed as there is currently no
mapping in p2m table for the ITS translation register (GITS_TRANSLATER).

A mapping is required in the p2m page tables so that the device can
generate the MSI interrupt writing to the GITS_TRANSLATER register.

The GITS_TRANSLATER register is a 32-bit register, so map a single page.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
This patch was originally picked up from [1], and commit description
loosely borrowed from [2].

Example SMMUv3 fault (qemu-system-aarch64 virt model), ITS base 0x8080000:

(XEN) SMMUv3: /smmuv3@9050000: event 0x10 received:
(XEN) SMMUv3: /smmuv3@9050000:  0x0000000800000010
(XEN) SMMUv3: /smmuv3@9050000:  0x0000008000000000
(XEN) SMMUv3: /smmuv3@9050000:  0x0000000008090040
(XEN) SMMUv3: /smmuv3@9050000:  0x0000000000000000

Example SMMUv2 fault (AMD/Xilinx Versal), ITS base 0xf9020000:

(XEN) smmu: /axi/smmu@fd800000: Unhandled context fault: fsr=0x402, 
iova=0xf9030040, fsynr=0x12, cb=0

v5->v6:
* switch to iommu_map() interface
* fix page_count argument
* style fixup
* use gprintk instead of printk
* add my Signed-off-by
* move to vgic_v3_its_init_virtual()

v4->v5:
* new patch

[1] https://lists.xenproject.org/archives/html/xen-devel/2023-07/msg00483.html
[2] 
https://gitlab.com/xen-project/people/bmarquis/xen-arm-poc/-/commit/6232a0d53377009bb7fbc3c3ab81d0153734be6b
---
 xen/arch/arm/vgic-v3-its.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
index 05429030b539..c35d5f9eb53e 100644
--- a/xen/arch/arm/vgic-v3-its.c
+++ b/xen/arch/arm/vgic-v3-its.c
@@ -1477,6 +1477,21 @@ static int vgic_v3_its_init_virtual(struct domain *d, 
paddr_t guest_addr,
 
     register_mmio_handler(d, &vgic_its_mmio_handler, guest_addr, SZ_64K, its);
 
+    if ( is_iommu_enabled(its->d) )
+    {
+        mfn_t mfn = maddr_to_mfn(its->doorbell_address);
+        unsigned int flush_flags = 0;
+        int ret = iommu_map(its->d, _dfn(mfn_x(mfn)), mfn, 1, IOMMUF_writable,
+                            &flush_flags);
+        if ( ret < 0 )
+        {
+            gprintk(XENLOG_ERR,
+                    "GICv3: Map ITS translation register %pd failed.\n",
+                    its->d);
+            return ret;
+        }
+    }
+
     /* Register the virtual ITS to be able to clean it up later. */
     list_add_tail(&its->vits_list, &d->arch.vgic.vits_list);
 
-- 
2.42.0