Re: [Qemu-devel] [PATCH v2 2/4] xen/mapcache: add an ability to create dummy mappings

[Stefano Stabellini]

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 

Reviewed-by: Stefano Stabellini 


> ---
>  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
> 

Re: [Qemu-devel] [PATCH v2 2/4] xen/mapcache: add an ability to create dummy mappings

[Paul Durrant]

> -Original Message-
> From: Igor Druzhinin
> Sent: 04 July 2017 16:48
> To: xen-de...@lists.xenproject.org; qemu-devel@nongnu.org
> Cc: Igor Druzhinin ; sstabell...@kernel.org;
> Anthony Perard ; Paul Durrant
> ; pbonz...@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 

Reviewed-by: Paul Durrant 

> ---
>  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

[Qemu-devel] [PATCH v2 2/4] xen/mapcache: add an ability to create dummy mappings

[Igor Druzhinin]

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 
---
 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