Dummys are simple anonymous mappings that are placed instead
of regular foreign mappings in certain situations when we need
to postpone the actual mapping but still have to give a
memory region to QEMU to play with.

This is planned to be used for restore on Xen.

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
---
 hw/i386/xen/xen-mapcache.c | 40 ++++++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/hw/i386/xen/xen-mapcache.c b/hw/i386/xen/xen-mapcache.c
index e60156c..cd4e746 100644
--- a/hw/i386/xen/xen-mapcache.c
+++ b/hw/i386/xen/xen-mapcache.c
@@ -53,6 +53,8 @@ typedef struct MapCacheEntry {
     uint8_t *vaddr_base;
     unsigned long *valid_mapping;
     uint8_t lock;
+#define XEN_MAPCACHE_ENTRY_DUMMY (1 << 0)
+    uint8_t flags;
     hwaddr size;
     struct MapCacheEntry *next;
 } MapCacheEntry;
@@ -150,7 +152,8 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
 
 static void xen_remap_bucket(MapCacheEntry *entry,
                              hwaddr size,
-                             hwaddr address_index)
+                             hwaddr address_index,
+                             bool dummy)
 {
     uint8_t *vaddr_base;
     xen_pfn_t *pfns;
@@ -177,11 +180,27 @@ static void xen_remap_bucket(MapCacheEntry *entry,
         pfns[i] = (address_index << (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT)) + i;
     }
 
-    vaddr_base = xenforeignmemory_map(xen_fmem, xen_domid, PROT_READ|PROT_WRITE,
-                                      nb_pfn, pfns, err);
-    if (vaddr_base == NULL) {
-        perror("xenforeignmemory_map");
-        exit(-1);
+    if (!dummy) {
+        vaddr_base = xenforeignmemory_map(xen_fmem, xen_domid,
+                                           PROT_READ|PROT_WRITE,
+                                           nb_pfn, pfns, err);
+        if (vaddr_base == NULL) {
+            perror("xenforeignmemory_map");
+            exit(-1);
+        }
+        entry->flags &= ~(XEN_MAPCACHE_ENTRY_DUMMY);
+    } else {
+        /*
+         * We create dummy mappings where we are unable to create a foreign
+         * mapping immediately due to certain circumstances (i.e. on resume now)
+         */
+        vaddr_base = mmap(NULL, size, PROT_READ|PROT_WRITE,
+                          MAP_ANON|MAP_SHARED, -1, 0);
+        if (vaddr_base == NULL) {
+            perror("mmap");
+            exit(-1);
+        }
+        entry->flags |= XEN_MAPCACHE_ENTRY_DUMMY;
     }
 
     entry->vaddr_base = vaddr_base;
@@ -211,6 +230,7 @@ static uint8_t *xen_map_cache_unlocked(hwaddr phys_addr, hwaddr size,
     hwaddr cache_size = size;
     hwaddr test_bit_size;
     bool translated = false;
+    bool dummy = false;
 
 tryagain:
     address_index  = phys_addr >> MCACHE_BUCKET_SHIFT;
@@ -262,14 +282,14 @@ tryagain:
     if (!entry) {
         entry = g_malloc0(sizeof (MapCacheEntry));
         pentry->next = entry;
-        xen_remap_bucket(entry, cache_size, address_index);
+        xen_remap_bucket(entry, cache_size, address_index, dummy);
     } else if (!entry->lock) {
         if (!entry->vaddr_base || entry->paddr_index != address_index ||
                 entry->size != cache_size ||
                 !test_bits(address_offset >> XC_PAGE_SHIFT,
                     test_bit_size >> XC_PAGE_SHIFT,
                     entry->valid_mapping)) {
-            xen_remap_bucket(entry, cache_size, address_index);
+            xen_remap_bucket(entry, cache_size, address_index, dummy);
         }
     }
 
@@ -282,6 +302,10 @@ tryagain:
             translated = true;
             goto tryagain;
         }
+        if (!dummy && runstate_check(RUN_STATE_INMIGRATE)) {
+            dummy = true;
+            goto tryagain;
+        }
         trace_xen_map_cache_return(NULL);
         return NULL;
     }
-- 
2.7.4

> -----Original Message-----
> From: Igor Druzhinin
> Sent: 04 July 2017 16:48
> To: xen-devel@lists.xenproject.org; qemu-devel@nongnu.org
> Cc: Igor Druzhinin <igor.druzhinin@citrix.com>; sstabellini@kernel.org;
> Anthony Perard <anthony.perard@citrix.com>; Paul Durrant
> <Paul.Durrant@citrix.com>; pbonzini@redhat.com
> Subject: [PATCH v2 2/4] xen/mapcache: add an ability to create dummy
> mappings
> 
> Dummys are simple anonymous mappings that are placed instead
> of regular foreign mappings in certain situations when we need
> to postpone the actual mapping but still have to give a
> memory region to QEMU to play with.
> 
> This is planned to be used for restore on Xen.
> 
> Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>

Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

> ---
>  hw/i386/xen/xen-mapcache.c | 40
> ++++++++++++++++++++++++++++++++--------
>  1 file changed, 32 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/i386/xen/xen-mapcache.c b/hw/i386/xen/xen-mapcache.c
> index e60156c..cd4e746 100644
> --- a/hw/i386/xen/xen-mapcache.c
> +++ b/hw/i386/xen/xen-mapcache.c
> @@ -53,6 +53,8 @@ typedef struct MapCacheEntry {
>      uint8_t *vaddr_base;
>      unsigned long *valid_mapping;
>      uint8_t lock;
> +#define XEN_MAPCACHE_ENTRY_DUMMY (1 << 0)
> +    uint8_t flags;
>      hwaddr size;
>      struct MapCacheEntry *next;
>  } MapCacheEntry;
> @@ -150,7 +152,8 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f,
> void *opaque)
> 
>  static void xen_remap_bucket(MapCacheEntry *entry,
>                               hwaddr size,
> -                             hwaddr address_index)
> +                             hwaddr address_index,
> +                             bool dummy)
>  {
>      uint8_t *vaddr_base;
>      xen_pfn_t *pfns;
> @@ -177,11 +180,27 @@ static void xen_remap_bucket(MapCacheEntry
> *entry,
>          pfns[i] = (address_index << (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT))
> + i;
>      }
> 
> -    vaddr_base = xenforeignmemory_map(xen_fmem, xen_domid,
> PROT_READ|PROT_WRITE,
> -                                      nb_pfn, pfns, err);
> -    if (vaddr_base == NULL) {
> -        perror("xenforeignmemory_map");
> -        exit(-1);
> +    if (!dummy) {
> +        vaddr_base = xenforeignmemory_map(xen_fmem, xen_domid,
> +                                           PROT_READ|PROT_WRITE,
> +                                           nb_pfn, pfns, err);
> +        if (vaddr_base == NULL) {
> +            perror("xenforeignmemory_map");
> +            exit(-1);
> +        }
> +        entry->flags &= ~(XEN_MAPCACHE_ENTRY_DUMMY);
> +    } else {
> +        /*
> +         * We create dummy mappings where we are unable to create a foreign
> +         * mapping immediately due to certain circumstances (i.e. on resume
> now)
> +         */
> +        vaddr_base = mmap(NULL, size, PROT_READ|PROT_WRITE,
> +                          MAP_ANON|MAP_SHARED, -1, 0);
> +        if (vaddr_base == NULL) {
> +            perror("mmap");
> +            exit(-1);
> +        }
> +        entry->flags |= XEN_MAPCACHE_ENTRY_DUMMY;
>      }
> 
>      entry->vaddr_base = vaddr_base;
> @@ -211,6 +230,7 @@ static uint8_t *xen_map_cache_unlocked(hwaddr
> phys_addr, hwaddr size,
>      hwaddr cache_size = size;
>      hwaddr test_bit_size;
>      bool translated = false;
> +    bool dummy = false;
> 
>  tryagain:
>      address_index  = phys_addr >> MCACHE_BUCKET_SHIFT;
> @@ -262,14 +282,14 @@ tryagain:
>      if (!entry) {
>          entry = g_malloc0(sizeof (MapCacheEntry));
>          pentry->next = entry;
> -        xen_remap_bucket(entry, cache_size, address_index);
> +        xen_remap_bucket(entry, cache_size, address_index, dummy);
>      } else if (!entry->lock) {
>          if (!entry->vaddr_base || entry->paddr_index != address_index ||
>                  entry->size != cache_size ||
>                  !test_bits(address_offset >> XC_PAGE_SHIFT,
>                      test_bit_size >> XC_PAGE_SHIFT,
>                      entry->valid_mapping)) {
> -            xen_remap_bucket(entry, cache_size, address_index);
> +            xen_remap_bucket(entry, cache_size, address_index, dummy);
>          }
>      }
> 
> @@ -282,6 +302,10 @@ tryagain:
>              translated = true;
>              goto tryagain;
>          }
> +        if (!dummy && runstate_check(RUN_STATE_INMIGRATE)) {
> +            dummy = true;
> +            goto tryagain;
> +        }
>          trace_xen_map_cache_return(NULL);
>          return NULL;
>      }
> --
> 2.7.4

On Tue, 4 Jul 2017, Igor Druzhinin wrote:
> Dummys are simple anonymous mappings that are placed instead
> of regular foreign mappings in certain situations when we need
> to postpone the actual mapping but still have to give a
> memory region to QEMU to play with.
> 
> This is planned to be used for restore on Xen.
> 
> Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>  hw/i386/xen/xen-mapcache.c | 40 ++++++++++++++++++++++++++++++++--------
>  1 file changed, 32 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/i386/xen/xen-mapcache.c b/hw/i386/xen/xen-mapcache.c
> index e60156c..cd4e746 100644
> --- a/hw/i386/xen/xen-mapcache.c
> +++ b/hw/i386/xen/xen-mapcache.c
> @@ -53,6 +53,8 @@ typedef struct MapCacheEntry {
>      uint8_t *vaddr_base;
>      unsigned long *valid_mapping;
>      uint8_t lock;
> +#define XEN_MAPCACHE_ENTRY_DUMMY (1 << 0)
> +    uint8_t flags;
>      hwaddr size;
>      struct MapCacheEntry *next;
>  } MapCacheEntry;
> @@ -150,7 +152,8 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
>  
>  static void xen_remap_bucket(MapCacheEntry *entry,
>                               hwaddr size,
> -                             hwaddr address_index)
> +                             hwaddr address_index,
> +                             bool dummy)
>  {
>      uint8_t *vaddr_base;
>      xen_pfn_t *pfns;
> @@ -177,11 +180,27 @@ static void xen_remap_bucket(MapCacheEntry *entry,
>          pfns[i] = (address_index << (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT)) + i;
>      }
>  
> -    vaddr_base = xenforeignmemory_map(xen_fmem, xen_domid, PROT_READ|PROT_WRITE,
> -                                      nb_pfn, pfns, err);
> -    if (vaddr_base == NULL) {
> -        perror("xenforeignmemory_map");
> -        exit(-1);
> +    if (!dummy) {
> +        vaddr_base = xenforeignmemory_map(xen_fmem, xen_domid,
> +                                           PROT_READ|PROT_WRITE,
> +                                           nb_pfn, pfns, err);
> +        if (vaddr_base == NULL) {
> +            perror("xenforeignmemory_map");
> +            exit(-1);
> +        }
> +        entry->flags &= ~(XEN_MAPCACHE_ENTRY_DUMMY);
> +    } else {
> +        /*
> +         * We create dummy mappings where we are unable to create a foreign
> +         * mapping immediately due to certain circumstances (i.e. on resume now)
> +         */
> +        vaddr_base = mmap(NULL, size, PROT_READ|PROT_WRITE,
> +                          MAP_ANON|MAP_SHARED, -1, 0);
> +        if (vaddr_base == NULL) {
> +            perror("mmap");
> +            exit(-1);
> +        }
> +        entry->flags |= XEN_MAPCACHE_ENTRY_DUMMY;
>      }
>  
>      entry->vaddr_base = vaddr_base;
> @@ -211,6 +230,7 @@ static uint8_t *xen_map_cache_unlocked(hwaddr phys_addr, hwaddr size,
>      hwaddr cache_size = size;
>      hwaddr test_bit_size;
>      bool translated = false;
> +    bool dummy = false;
>  
>  tryagain:
>      address_index  = phys_addr >> MCACHE_BUCKET_SHIFT;
> @@ -262,14 +282,14 @@ tryagain:
>      if (!entry) {
>          entry = g_malloc0(sizeof (MapCacheEntry));
>          pentry->next = entry;
> -        xen_remap_bucket(entry, cache_size, address_index);
> +        xen_remap_bucket(entry, cache_size, address_index, dummy);
>      } else if (!entry->lock) {
>          if (!entry->vaddr_base || entry->paddr_index != address_index ||
>                  entry->size != cache_size ||
>                  !test_bits(address_offset >> XC_PAGE_SHIFT,
>                      test_bit_size >> XC_PAGE_SHIFT,
>                      entry->valid_mapping)) {
> -            xen_remap_bucket(entry, cache_size, address_index);
> +            xen_remap_bucket(entry, cache_size, address_index, dummy);
>          }
>      }
>  
> @@ -282,6 +302,10 @@ tryagain:
>              translated = true;
>              goto tryagain;
>          }
> +        if (!dummy && runstate_check(RUN_STATE_INMIGRATE)) {
> +            dummy = true;
> +            goto tryagain;
> +        }
>          trace_xen_map_cache_return(NULL);
>          return NULL;
>      }
> -- 
> 2.7.4
>