diff mbox

[Xen-devel,v3,3/8] tools: arm: move magic pfns out of guest RAM region

Message ID 1398690132-5651-3-git-send-email-ian.campbell@citrix.com
State New
Headers show

Commit Message

Ian Campbell April 28, 2014, 1:02 p.m. UTC 
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>
--
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>
---
 tools/libxc/xc_dom_arm.c      |   14 ++++++++------
 xen/include/public/arch-arm.h |    3 +++
 2 files changed, 11 insertions(+), 6 deletions(-)

Comments

Ian Jackson May 2, 2014, 2:36 p.m. UTC | #1 
Ian Campbell writes ("[PATCH v3 3/8] 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.
...
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Acked-by: Julien Grall <julien.grall@linaro.org>

I haven't checked the semantics of this from an arm architecture pov.
I hope Julien has :-).  But with a tools hat on:

Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

Ian.
diff mbox

Patch

diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
index 46dfc36..74917c3 100644
--- 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" > %"PRIx64,
-                  __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 dd53c94..6630f36 100644
--- 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