[Xen-devel] [RFC PATCH v2 08/26] ARM: GICv3 ITS: map device and LPIs to the ITS on physdev_op hypercall

[Andre Przywara <andre.przywara@xxxxxxx>]

To get MSIs from devices forwarded to a CPU, we need to name the device
and its MSIs by mapping them to an ITS.
Since this involves queueing commands to the ITS command queue, we can't
really afford to do this during the guest's runtime, as this would open
up a denial-of-service attack vector.
So we require every device with MSI interrupts to be mapped explicitly by
Dom0. For Dom0 itself we can just use the existing PCI physdev_op
hypercalls, which the existing Linux kernel issues already.
So upon receipt of this hypercall we map the device to the hardware ITS
and prepare it to be later mapped by the virtual ITS by using the very
same device ID (for Dom0 only).
Also we ask for mapping 32 LPIs to cover 32 MSIs that the device may
use.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
 xen/arch/arm/physdev.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/xen/arch/arm/physdev.c b/xen/arch/arm/physdev.c
index 27bbbda..d9e6be3 100644
--- a/xen/arch/arm/physdev.c
+++ b/xen/arch/arm/physdev.c
@@ -9,11 +9,35 @@
 #include <xen/lib.h>
 #include <xen/errno.h>
 #include <xen/sched.h>
+#include <xen/guest_access.h>
+#include <asm/gic-its.h>
 #include <asm/hypercall.h>
 
 
 int do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 {
+    struct physdev_manage_pci manage;
+    struct domain *dom0;
+    u32 devid;
+    int ret;
+
+    switch (cmd)
+    {
+        case PHYSDEVOP_manage_pci_add:
+        case PHYSDEVOP_manage_pci_remove:
+            if ( copy_from_guest(&manage, arg, 1) != 0 )
+                return -EFAULT;
+
+            dom0 = hardware_domain;
+            devid = manage.bus << 8 | manage.devfn;
+            /* Allocate an ITS device table with space for 32 MSIs */
+            ret = gicv3_its_map_device(dom0, devid, devid, 5,
+                                       cmd == PHYSDEVOP_manage_pci_add);
+
+            put_domain(dom0);
+            return ret;
+    }
+
     gdprintk(XENLOG_DEBUG, "PHYSDEVOP cmd=%d: not implemented\n", cmd);
     return -ENOSYS;
 }
-- 
2.9.0


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