[PATCH 2/3] xen/arm, tools: Add a new HVM_PARAM_MAGIC_BASE_PFN key in HVMOP

[Henry Wang <xin.wang2@xxxxxxx>]

For use cases such as Dom0less PV drivers, a mechanism to communicate
Dom0less DomU's static data with the runtime control plane (Dom0) is
needed. Since on Arm HVMOP is already the existing approach to address
such use cases (for example the allocation of HVM_PARAM_CALLBACK_IRQ),
add a new HVMOP key HVM_PARAM_MAGIC_BASE_PFN for storing the magic
page region base PFN. The value will be set at Dom0less DomU
construction time after Dom0less DomU's magic page region has been
allocated.

To keep consistent, also set the value for HVM_PARAM_MAGIC_BASE_PFN
for libxl guests in alloc_magic_pages().

Reported-by: Alec Kwapis <alec.kwapis@xxxxxxxxxxxxx>
Signed-off-by: Henry Wang <xin.wang2@xxxxxxx>
---
 tools/libs/guest/xg_dom_arm.c   | 2 ++
 xen/arch/arm/dom0less-build.c   | 2 ++
 xen/arch/arm/hvm.c              | 1 +
 xen/include/public/hvm/params.h | 1 +
 4 files changed, 6 insertions(+)

diff --git a/tools/libs/guest/xg_dom_arm.c b/tools/libs/guest/xg_dom_arm.c
index 8cc7f27dbb..3c08782d1d 100644
--- a/tools/libs/guest/xg_dom_arm.c
+++ b/tools/libs/guest/xg_dom_arm.c
@@ -74,6 +74,8 @@ static int alloc_magic_pages(struct xc_dom_image *dom)
     xc_clear_domain_page(dom->xch, dom->guest_domid, base + 
MEMACCESS_PFN_OFFSET);
     xc_clear_domain_page(dom->xch, dom->guest_domid, dom->vuart_gfn);
 
+    xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_MAGIC_BASE_PFN,
+            base);
     xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_CONSOLE_PFN,
             dom->console_pfn);
     xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_STORE_PFN,
diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
index 40dc85c759..72187c167d 100644
--- a/xen/arch/arm/dom0less-build.c
+++ b/xen/arch/arm/dom0less-build.c
@@ -861,6 +861,8 @@ static int __init construct_domU(struct domain *d,
             free_domheap_pages(magic_pg, get_order_from_pages(NR_MAGIC_PAGES));
             return rc;
         }
+
+        d->arch.hvm.params[HVM_PARAM_MAGIC_BASE_PFN] = gfn_x(gfn);
     }
 
     return rc;
diff --git a/xen/arch/arm/hvm.c b/xen/arch/arm/hvm.c
index 0989309fea..fa6141e30c 100644
--- a/xen/arch/arm/hvm.c
+++ b/xen/arch/arm/hvm.c
@@ -55,6 +55,7 @@ static int hvm_allow_get_param(const struct domain *d, 
unsigned int param)
     case HVM_PARAM_STORE_EVTCHN:
     case HVM_PARAM_CONSOLE_PFN:
     case HVM_PARAM_CONSOLE_EVTCHN:
+    case HVM_PARAM_MAGIC_BASE_PFN:
         return 0;
 
         /*
diff --git a/xen/include/public/hvm/params.h b/xen/include/public/hvm/params.h
index a22b4ed45d..c1720b33b9 100644
--- a/xen/include/public/hvm/params.h
+++ b/xen/include/public/hvm/params.h
@@ -76,6 +76,7 @@
  */
 #define HVM_PARAM_STORE_PFN    1
 #define HVM_PARAM_STORE_EVTCHN 2
+#define HVM_PARAM_MAGIC_BASE_PFN    3
 
 #define HVM_PARAM_IOREQ_PFN    5
 
-- 
2.34.1