[PATCH v3 27/32] libxc: change the position of the special pages

[Roger Pau Monne <roger.pau@citrix.com>]

Change the physical memory address of the special pages when there are no
emulated devices. On HVM guests the special pages have always been reserved
so that they end at the 0xff000 pfn, but there are some problems with this
approach when used without emulated devices:

 - If we want to allow HVMlite to be used for Dom0 those special pages
   cannot be placed inside of the MMIO hole or else they may clash with MMIO
   regions of physical devices passed-through to Dom0.
 - If there's no emulated devices the guests needs to access the console
   page and the command line very early during boot. This is a problem for
   FreeBSD at least, since the early page tables only map memory up to 1GiB.

So instead append the special pages after the kernel and ramdisk. The guest
must make sure it figures out the position of those pages very early during
boot, since the region is not marked as reserved in the memory map.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
---
 tools/libxc/xc_dom_x86.c | 50 ++++++++++++++++++++++++++++++------------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index 45b1f03..1195400 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -58,15 +58,27 @@
 #define SPECIALPAGE_IDENT_PT 6
 #define SPECIALPAGE_CONSOLE  7
 #define NR_SPECIAL_PAGES     8
-#define special_pfn(x) (0xff000u - NR_SPECIAL_PAGES + (x))
+#define LAST_SPECIAL_PFN     0xff000u
 
 #define NR_IOREQ_SERVER_PAGES 8
-#define ioreq_server_pfn(x) (special_pfn(0) - NR_IOREQ_SERVER_PAGES + (x))
+#define ioreq_server_pfn(x, dom) (special_pfn(0, dom) - NR_IOREQ_SERVER_PAGES + (x))
 
 #define bits_to_mask(bits)       (((xen_vaddr_t)1 << (bits))-1)
 #define round_down(addr, mask)   ((addr) & ~(mask))
 #define round_up(addr, mask)     ((addr) | (mask))
 
+static unsigned long special_pfn(int index, struct xc_dom_image *dom)
+{
+    unsigned long start_pfn;
+
+    if ( dom->emulation )
+        return (LAST_SPECIAL_PFN - NR_SPECIAL_PAGES + index);
+
+    start_pfn = (dom->virt_alloc_end - dom->parms.virt_base) >>
+                XC_DOM_PAGE_SHIFT(dom);
+    return (start_pfn + index);
+}
+
 /* get guest IO ABI protocol */
 const char *xc_domain_get_native_protocol(xc_interface *xch,
                                           uint32_t domid)
@@ -502,7 +514,7 @@ static void build_hvm_info(void *hvm_info_page, struct xc_dom_image *dom)
     /* Memory parameters. */
     hvm_info->low_mem_pgend = dom->lowmem_end >> PAGE_SHIFT;
     hvm_info->high_mem_pgend = dom->highmem_end >> PAGE_SHIFT;
-    hvm_info->reserved_mem_pgstart = ioreq_server_pfn(0);
+    hvm_info->reserved_mem_pgstart = ioreq_server_pfn(0, dom);
 
     /* Finish with the checksum. */
     for ( i = 0, sum = 0; i < hvm_info->length; i++ )
@@ -532,7 +544,7 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
 
     /* Allocate and clear special pages. */
     for ( i = 0; i < NR_SPECIAL_PAGES; i++ )
-        special_array[i] = special_pfn(i);
+        special_array[i] = special_pfn(i, dom);
 
     rc = xc_domain_populate_physmap_exact(xch, domid, NR_SPECIAL_PAGES, 0, 0,
                                           special_array);
@@ -542,23 +554,23 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
         goto error_out;
     }
 
-    if ( xc_clear_domain_pages(xch, domid, special_pfn(0), NR_SPECIAL_PAGES) )
+    if ( xc_clear_domain_pages(xch, domid, special_pfn(0, dom), NR_SPECIAL_PAGES) )
             goto error_out;
 
     xc_hvm_param_set(xch, domid, HVM_PARAM_STORE_PFN,
-                     special_pfn(SPECIALPAGE_XENSTORE));
+                     special_pfn(SPECIALPAGE_XENSTORE, dom));
     xc_hvm_param_set(xch, domid, HVM_PARAM_BUFIOREQ_PFN,
-                     special_pfn(SPECIALPAGE_BUFIOREQ));
+                     special_pfn(SPECIALPAGE_BUFIOREQ, dom));
     xc_hvm_param_set(xch, domid, HVM_PARAM_IOREQ_PFN,
-                     special_pfn(SPECIALPAGE_IOREQ));
+                     special_pfn(SPECIALPAGE_IOREQ, dom));
     xc_hvm_param_set(xch, domid, HVM_PARAM_CONSOLE_PFN,
-                     special_pfn(SPECIALPAGE_CONSOLE));
+                     special_pfn(SPECIALPAGE_CONSOLE, dom));
     xc_hvm_param_set(xch, domid, HVM_PARAM_PAGING_RING_PFN,
-                     special_pfn(SPECIALPAGE_PAGING));
+                     special_pfn(SPECIALPAGE_PAGING, dom));
     xc_hvm_param_set(xch, domid, HVM_PARAM_MONITOR_RING_PFN,
-                     special_pfn(SPECIALPAGE_ACCESS));
+                     special_pfn(SPECIALPAGE_ACCESS, dom));
     xc_hvm_param_set(xch, domid, HVM_PARAM_SHARING_RING_PFN,
-                     special_pfn(SPECIALPAGE_SHARING));
+                     special_pfn(SPECIALPAGE_SHARING, dom));
 
     if ( dom->emulation )
     {
@@ -567,7 +579,7 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
          * server will use the IOREQ and BUFIOREQ special pages above.
          */
         for ( i = 0; i < NR_IOREQ_SERVER_PAGES; i++ )
-            ioreq_server_array[i] = ioreq_server_pfn(i);
+            ioreq_server_array[i] = ioreq_server_pfn(i, dom);
 
         rc = xc_domain_populate_physmap_exact(xch, domid, NR_IOREQ_SERVER_PAGES, 0,
                                               0, ioreq_server_array);
@@ -577,13 +589,13 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
             goto error_out;
         }
 
-        if ( xc_clear_domain_pages(xch, domid, ioreq_server_pfn(0),
+        if ( xc_clear_domain_pages(xch, domid, ioreq_server_pfn(0, dom),
                                    NR_IOREQ_SERVER_PAGES) )
                 goto error_out;
 
         /* Tell the domain where the pages are and how many there are */
         xc_hvm_param_set(xch, domid, HVM_PARAM_IOREQ_SERVER_PFN,
-                         ioreq_server_pfn(0));
+                         ioreq_server_pfn(0, dom));
         xc_hvm_param_set(xch, domid, HVM_PARAM_NR_IOREQ_SERVER_PAGES,
                          NR_IOREQ_SERVER_PAGES);
     }
@@ -594,17 +606,17 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
      */
     if ( (ident_pt = xc_map_foreign_range(
               xch, domid, PAGE_SIZE, PROT_READ | PROT_WRITE,
-              special_pfn(SPECIALPAGE_IDENT_PT))) == NULL )
+              special_pfn(SPECIALPAGE_IDENT_PT, dom))) == NULL )
         goto error_out;
     for ( i = 0; i < PAGE_SIZE / sizeof(*ident_pt); i++ )
         ident_pt[i] = ((i << 22) | _PAGE_PRESENT | _PAGE_RW | _PAGE_USER |
                        _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE);
     munmap(ident_pt, PAGE_SIZE);
     xc_hvm_param_set(xch, domid, HVM_PARAM_IDENT_PT,
-                     special_pfn(SPECIALPAGE_IDENT_PT) << PAGE_SHIFT);
+                     special_pfn(SPECIALPAGE_IDENT_PT, dom) << PAGE_SHIFT);
 
-    dom->console_pfn = special_pfn(SPECIALPAGE_CONSOLE);
-    dom->xenstore_pfn = special_pfn(SPECIALPAGE_XENSTORE);
+    dom->console_pfn = special_pfn(SPECIALPAGE_CONSOLE, dom);
+    dom->xenstore_pfn = special_pfn(SPECIALPAGE_XENSTORE, dom);
     dom->parms.virt_hypercall = -1;
 
     rc = 0;
-- 
1.9.5 (Apple Git-50.3)


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