tools: arm: move magic pfns out of guest RAM region

Because toolstacks (at least libxl) only allow RAM to be specified in 1M
increments these two pages were effectively costing 1M of guest RAM space.

Since these pages don't actually need to live in RAM just move them out.

With this a guest can now use the full 768M of the address space reserved
for RAM. (ok, not that impressive, but it simplifies things later)

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
--
v3: make the size of the region explicit.
v2: remove spurious w/s change

tools: arm: make the size of the magic page region explicit

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
index d5831a219caebdbd61ab2d424c663adc45beb799..81d5fc72be9d02470f3a85c061e6c9d7a0710e17 100644 (file)
--- a/tools/libxc/xc_dom_arm.c
+++ b/tools/libxc/xc_dom_arm.c
@@ -58,12 +58,15 @@ static int setup_pgtables_arm(struct xc_dom_image *dom)
 static int alloc_magic_pages(struct xc_dom_image *dom)
 {
     int rc, i;
+    const xen_pfn_t base = GUEST_MAGIC_BASE >> XC_PAGE_SHIFT;
     xen_pfn_t p2m[NR_MAGIC_PAGES];
 
+    XC_BUILD_BUG_ON(NR_MAGIC_PAGES > GUEST_MAGIC_SIZE >> XC_PAGE_SHIFT);
+
     DOMPRINTF_CALLED(dom->xch);
 
     for (i = 0; i < NR_MAGIC_PAGES; i++)
-        p2m[i] = dom->rambase_pfn + dom->total_pages + i;
+        p2m[i] = base + i;
 
     rc = xc_domain_populate_physmap_exact(
             dom->xch, dom->guest_domid, NR_MAGIC_PAGES,
@@ -71,8 +74,8 @@ static int alloc_magic_pages(struct xc_dom_image *dom)
     if ( rc < 0 )
         return rc;
 
-    dom->console_pfn = dom->rambase_pfn + dom->total_pages + CONSOLE_PFN_OFFSET;
-    dom->xenstore_pfn = dom->rambase_pfn + dom->total_pages + XENSTORE_PFN_OFFSET;
+    dom->console_pfn = base + CONSOLE_PFN_OFFSET;
+    dom->xenstore_pfn = base + XENSTORE_PFN_OFFSET;
 
     xc_clear_domain_page(dom->xch, dom->guest_domid, dom->console_pfn);
     xc_clear_domain_page(dom->xch, dom->guest_domid, dom->xenstore_pfn);
@@ -272,12 +275,11 @@ int arch_setup_meminit(struct xc_dom_image *dom)
         return -1;
     }
 
-    if ( ramsize > GUEST_RAM_SIZE - NR_MAGIC_PAGES*XC_PAGE_SIZE )
+    if ( ramsize > GUEST_RAM_SIZE )
     {
         DOMPRINTF("%s: ram size is too large for guest address space: "
                   "%"PRIx64" > %llx",
-                  __FUNCTION__, ramsize,
-                  GUEST_RAM_SIZE - NR_MAGIC_PAGES*XC_PAGE_SIZE);
+                  __FUNCTION__, ramsize, GUEST_RAM_SIZE);
         return -1;
     }
 

diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
index dd53c9402860873ea637b846e6138014cc417a4a..6630f36bc9d6561b955b4638ba70e372f4f64ff6 100644 (file)
--- a/xen/include/public/arch-arm.h
+++ b/xen/include/public/arch-arm.h
@@ -375,6 +375,9 @@ typedef uint64_t xen_callback_t;
 #define GUEST_GNTTAB_BASE 0xb0000000ULL
 #define GUEST_GNTTAB_SIZE 0x00020000ULL
 
+#define GUEST_MAGIC_BASE  0xc0000000ULL
+#define GUEST_MAGIC_SIZE  0x01000000ULL
+
 /* Interrupts */
 #define GUEST_TIMER_VIRT_PPI    27
 #define GUEST_TIMER_PHYS_S_PPI  29