xen: arm: improve VMID allocation.

The VMID field is 8 bits. Rather than allowing only up to 256 VMs per host
reboot before things start "acting strange" instead maintain a simple bitmap
of used VMIDs and allocate them statically to guests upon creation.

This limits us to 256 concurrent VMs which is a reasonable improvement.
Eventually we will want a proper scheme to allocate VMIDs on context switch.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index a00069bdbd..c660820a3d 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -20,6 +20,9 @@ struct p2m_domain {
     uint8_t vmid;
 };
 
+/* Initialise vmid allocator */
+void p2m_vmid_allocator_init(void);
+
 /* Init the datastructures for later use by the p2m code */
 int p2m_init(struct domain *d);