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[Xen-devel,v2,3/8] tools: arm: move magic pfns out of guest RAM region

Message ID 1398424967-9306-3-git-send-email-ian.campbell@citrix.com
State New
Headers show

Commit Message

Ian Campbell April 25, 2014, 11:22 a.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>
--
v2: remove spurious w/s change
---
 tools/libxc/xc_dom_arm.c      |   12 ++++++------
 xen/include/public/arch-arm.h |    2 ++
 2 files changed, 8 insertions(+), 6 deletions(-)

Comments

Julien Grall April 25, 2014, 12:09 p.m. UTC | #1 
On 25/04/14 12:22, Ian Campbell wrote:
> diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
> index dd53c94..a94d16b 100644
> --- a/xen/include/public/arch-arm.h
> +++ b/xen/include/public/arch-arm.h
> @@ -375,6 +375,8 @@ typedef uint64_t xen_callback_t;
>   #define GUEST_GNTTAB_BASE 0xb0000000ULL
>   #define GUEST_GNTTAB_SIZE 0x00020000ULL
>
> +#define GUEST_MAGIC_BASE  0xc0000000ULL
> +

I'm wondering if we need to move NR_MAGIC_PAGES or add a comment in 
arch-arm.h if someone wants to bump the number page magic page.

Or perhaps a BUG_ON in libxc to check at compilation time the hole is 
large enought to hold all special pages.
Ian Campbell April 25, 2014, 12:22 p.m. UTC | #2 
On Fri, 2014-04-25 at 13:09 +0100, Julien Grall wrote:
> 
> On 25/04/14 12:22, Ian Campbell wrote:
> > diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
> > index dd53c94..a94d16b 100644
> > --- a/xen/include/public/arch-arm.h
> > +++ b/xen/include/public/arch-arm.h
> > @@ -375,6 +375,8 @@ typedef uint64_t xen_callback_t;
> >   #define GUEST_GNTTAB_BASE 0xb0000000ULL
> >   #define GUEST_GNTTAB_SIZE 0x00020000ULL
> >
> > +#define GUEST_MAGIC_BASE  0xc0000000ULL
> > +
> 
> I'm wondering if we need to move NR_MAGIC_PAGES or add a comment in 
> arch-arm.h if someone wants to bump the number page magic page.
> 
> Or perhaps a BUG_ON in libxc to check at compilation time the hole is 
> large enought to hold all special pages.

I'll add GUEST_MAGIC_SIZE and a (BUILD_)BUG_ON to check against it.

Ian.
diff mbox

Patch

diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
index 46dfc36..5760bb1 100644
--- a/tools/libxc/xc_dom_arm.c
+++ b/tools/libxc/xc_dom_arm.c
@@ -58,12 +58,13 @@  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 >> PAGE_SHIFT;
     xen_pfn_t p2m[NR_MAGIC_PAGES];
 
     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 +72,8 @@  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 +273,11 @@  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..a94d16b 100644
--- a/xen/include/public/arch-arm.h
+++ b/xen/include/public/arch-arm.h
@@ -375,6 +375,8 @@  typedef uint64_t xen_callback_t;
 #define GUEST_GNTTAB_BASE 0xb0000000ULL
 #define GUEST_GNTTAB_SIZE 0x00020000ULL
 
+#define GUEST_MAGIC_BASE  0xc0000000ULL
+
 /* Interrupts */
 #define GUEST_TIMER_VIRT_PPI    27
 #define GUEST_TIMER_PHYS_S_PPI  29