[xen master] init-dom0less: allocate xenstore page if not already allocated

[patchbot@xxxxxxx]

commit 56b8e80812f5ba98f6085d2c08c620d9a2a3479e
Author:     Stefano Stabellini <stefano.stabellini@xxxxxxx>
AuthorDate: Fri Jan 31 16:29:46 2025 -0800
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxx>
CommitDate: Mon Mar 3 16:05:13 2025 -0800

    init-dom0less: allocate xenstore page if not already allocated
    
    We check if the xenstore page is already allocated. If yes, there is
    nothing to do. If no, we proceed allocating it to support old unpatched
    Linux kernels.
    
    Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
    Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
---
 tools/helpers/init-dom0less.c | 54 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 2 deletions(-)

diff --git a/tools/helpers/init-dom0less.c b/tools/helpers/init-dom0less.c
index 2b51965fa7..17579fe2e8 100644
--- a/tools/helpers/init-dom0less.c
+++ b/tools/helpers/init-dom0less.c
@@ -16,8 +16,34 @@
 
 #include "init-dom-json.h"
 
+#define XENSTORE_PFN_OFFSET 1
 #define STR_MAX_LENGTH 128
 
+static int alloc_xs_page(struct xc_interface_core *xch,
+                         libxl_dominfo *info,
+                         uint64_t *xenstore_pfn)
+{
+    int rc;
+    const xen_pfn_t base = GUEST_MAGIC_BASE >> XC_PAGE_SHIFT;
+    xen_pfn_t p2m = base + XENSTORE_PFN_OFFSET;
+
+    rc = xc_domain_setmaxmem(xch, info->domid,
+                             info->max_memkb + (XC_PAGE_SIZE/1024));
+    if (rc < 0)
+        return rc;
+
+    rc = xc_domain_populate_physmap_exact(xch, info->domid, 1, 0, 0, &p2m);
+    if (rc < 0)
+        return rc;
+
+    *xenstore_pfn = base + XENSTORE_PFN_OFFSET;
+    rc = xc_clear_domain_page(xch, info->domid, *xenstore_pfn);
+    if (rc < 0)
+        return rc;
+
+    return 0;
+}
+
 static int get_xs_page(struct xc_interface_core *xch, libxl_dominfo *info,
                        uint64_t *xenstore_pfn)
 {
@@ -233,9 +259,33 @@ static int init_domain(struct xs_handle *xsh,
         return 0;
 
     /* Get xenstore page */
-    if (get_xs_page(xch, info, &xenstore_pfn) != 0) {
-        printf("Error on getting xenstore page\n");
+    if (get_xs_page(xch, info, &xenstore_pfn) != 0)
         return 1;
+
+    if (xenstore_pfn == ~0ULL) {
+        struct xenstore_domain_interface *intf;
+
+        rc = alloc_xs_page(xch, info, &xenstore_pfn);
+        if (rc != 0) {
+            printf("Error on getting xenstore page\n");
+            return 1;
+        }
+
+        intf = xenforeignmemory_map(xfh, info->domid, PROT_READ | PROT_WRITE, 
1,
+                                    &xenstore_pfn, NULL);
+        if (!intf) {
+            printf("Error mapping xenstore page\n");
+            return 1;
+        }
+
+        intf->connection = XENSTORE_RECONNECT;
+        xenforeignmemory_unmap(xfh, intf, 1);
+
+        /* Now everything is ready: set HVM_PARAM_STORE_PFN */
+        rc = xc_hvm_param_set(xch, info->domid, HVM_PARAM_STORE_PFN,
+                xenstore_pfn);
+        if (rc < 0)
+            return rc;
     }
 
     rc = xc_dom_gnttab_seed(xch, info->domid, true,
--
generated by git-patchbot for /home/xen/git/xen.git#master