[PATCH v7 0/8] xen: Support grant mappings

[PATCH v7 0/8] xen: Support grant mappings

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

Hi,

Grant mappings are a mechanism in Xen for guests to grant each other
permissions to map and share pages. These grants can be temporary
so both map and unmaps must be respected. See here for more info:
https://github.com/xen-project/xen/blob/master/docs/misc/grant-tables.txt

Currently, the primary use-case for grants in QEMU, is with VirtIO backends.
Grant mappings will only work with models that use the address_space_map/unmap
interfaces, any other access will fail with appropriate error messages.

In response to feedback we got on v3, later version switch approach
from adding new MemoryRegion types and map/unmap hooks to instead reusing
the existing xen_map_cache() hooks (with extensions). Almost all of the
changes are now contained to the Xen modules.

This approach also refactors the mapcache to support multiple instances
(one for existing foreign mappings and another for grant mappings).

I've only enabled grants for the ARM PVH machine since that is what
I can currently test on.

Cheers,
Edgar

ChangeLog:

v6 -> v7:
* Use g_autofree in xen_remap_bucket().
* Flatten nested if-statements in xen_map_cache().
* Fix typo in error message in xen_map_cache().

v5 -> v6:
* Correct passing of ram_addr_offset in xen_replace_cache_entry_unlocked.

v4 -> v5:
* Compute grant_ref from address_index to xen_remap_bucket().
* Rename grant_is_write to is_write.
* Remove unnecessary + mc->bucket_size - 1 in
  xen_invalidate_map_cache_entry_unlocked().
* Remove use of global mapcache in refactor of
  xen_replace_cache_entry_unlocked().
* Add error checking for xengnttab_unmap().
* Add assert in xen_replace_cache_entry_unlocked() against grant mappings.
* Fix memory leak when freeing first entry in mapcache buckets.
* Assert that bucket_shift is >= XC_PAGE_SHIFT when creating mapcache.
* Add missing use of xen_mr_is_memory() in hw/xen/xen-hvm-common.c.
* Rebase with master.

v3 -> v4:
* Reuse existing xen_map_cache hooks.
* Reuse existing map-cache for both foreign and grant mappings.
* Only enable grants for the ARM PVH machine (removed i386).

v2 -> v3:
* Drop patch 1/7. This was done because device unplug is an x86-only case.
* Add missing qemu_mutex_unlock() before return.

v1 -> v2:
* Split patch 2/7 to keep phymem.c changes in a separate.
* In patch "xen: add map and unmap callbacks for grant" add check for total
  allowed grant < XEN_MAX_VIRTIO_GRANTS.
* Fix formatting issues and re-based with master latest.


Edgar E. Iglesias (8):
  xen: mapcache: Make MCACHE_BUCKET_SHIFT runtime configurable
  xen: mapcache: Unmap first entries in buckets
  xen: Add xen_mr_is_memory()
  softmmu: xen: Always pass offset + addr to xen_map_cache
  softmmu: Replace check for RAMBlock offset 0 with xen_mr_is_memory
  xen: mapcache: Pass the ram_addr offset to xen_map_cache()
  xen: mapcache: Add support for grant mappings
  hw/arm: xen: Enable use of grant mappings

 hw/arm/xen_arm.c                |   5 +
 hw/xen/xen-hvm-common.c         |  18 ++-
 hw/xen/xen-mapcache.c           | 234 ++++++++++++++++++++++++--------
 include/hw/xen/xen-hvm-common.h |   3 +
 include/sysemu/xen-mapcache.h   |   2 +
 include/sysemu/xen.h            |  15 ++
 system/physmem.c                |  12 +-
 7 files changed, 224 insertions(+), 65 deletions(-)


base-commit: 70581940cabcc51b329652becddfbc6a261b1b83
-- 
2.40.1

[PATCH v7 1/8] xen: mapcache: Make MCACHE_BUCKET_SHIFT runtime configurable

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

Make MCACHE_BUCKET_SHIFT runtime configurable per cache instance.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
---
 hw/xen/xen-mapcache.c | 54 ++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 21 deletions(-)

diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index fa6813b1ad..bc860f4373 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -23,13 +23,10 @@
 
 
 #if HOST_LONG_BITS == 32
-#  define MCACHE_BUCKET_SHIFT 16
 #  define MCACHE_MAX_SIZE     (1UL<<31) /* 2GB Cap */
 #else
-#  define MCACHE_BUCKET_SHIFT 20
 #  define MCACHE_MAX_SIZE     (1UL<<35) /* 32GB Cap */
 #endif
-#define MCACHE_BUCKET_SIZE (1UL << MCACHE_BUCKET_SHIFT)
 
 /* This is the size of the virtual address space reserve to QEMU that will not
  * be use by MapCache.
@@ -65,7 +62,8 @@ typedef struct MapCache {
     /* For most cases (>99.9%), the page address is the same. */
     MapCacheEntry *last_entry;
     unsigned long max_mcache_size;
-    unsigned int mcache_bucket_shift;
+    unsigned int bucket_shift;
+    unsigned long bucket_size;
 
     phys_offset_to_gaddr_t phys_offset_to_gaddr;
     QemuMutex lock;
@@ -95,11 +93,14 @@ static inline int test_bits(int nr, int size, const unsigned long *addr)
 
 static MapCache *xen_map_cache_init_single(phys_offset_to_gaddr_t f,
                                            void *opaque,
+                                           unsigned int bucket_shift,
                                            unsigned long max_size)
 {
     unsigned long size;
     MapCache *mc;
 
+    assert(bucket_shift >= XC_PAGE_SHIFT);
+
     mc = g_new0(MapCache, 1);
 
     mc->phys_offset_to_gaddr = f;
@@ -108,12 +109,14 @@ static MapCache *xen_map_cache_init_single(phys_offset_to_gaddr_t f,
 
     QTAILQ_INIT(&mc->locked_entries);
 
+    mc->bucket_shift = bucket_shift;
+    mc->bucket_size = 1UL << bucket_shift;
     mc->max_mcache_size = max_size;
 
     mc->nr_buckets =
         (((mc->max_mcache_size >> XC_PAGE_SHIFT) +
-          (1UL << (MCACHE_BUCKET_SHIFT - XC_PAGE_SHIFT)) - 1) >>
-         (MCACHE_BUCKET_SHIFT - XC_PAGE_SHIFT));
+          (1UL << (bucket_shift - XC_PAGE_SHIFT)) - 1) >>
+         (bucket_shift - XC_PAGE_SHIFT));
 
     size = mc->nr_buckets * sizeof(MapCacheEntry);
     size = (size + XC_PAGE_SIZE - 1) & ~(XC_PAGE_SIZE - 1);
@@ -126,6 +129,13 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
 {
     struct rlimit rlimit_as;
     unsigned long max_mcache_size;
+    unsigned int bucket_shift;
+
+    if (HOST_LONG_BITS == 32) {
+        bucket_shift = 16;
+    } else {
+        bucket_shift = 20;
+    }
 
     if (geteuid() == 0) {
         rlimit_as.rlim_cur = RLIM_INFINITY;
@@ -146,7 +156,9 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
         }
     }
 
-    mapcache = xen_map_cache_init_single(f, opaque, max_mcache_size);
+    mapcache = xen_map_cache_init_single(f, opaque,
+                                         bucket_shift,
+                                         max_mcache_size);
     setrlimit(RLIMIT_AS, &rlimit_as);
 }
 
@@ -195,7 +207,7 @@ static void xen_remap_bucket(MapCache *mc,
     entry->valid_mapping = NULL;
 
     for (i = 0; i < nb_pfn; i++) {
-        pfns[i] = (address_index << (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT)) + i;
+        pfns[i] = (address_index << (mc->bucket_shift - XC_PAGE_SHIFT)) + i;
     }
 
     /*
@@ -266,8 +278,8 @@ static uint8_t *xen_map_cache_unlocked(MapCache *mc,
     bool dummy = false;
 
 tryagain:
-    address_index  = phys_addr >> MCACHE_BUCKET_SHIFT;
-    address_offset = phys_addr & (MCACHE_BUCKET_SIZE - 1);
+    address_index  = phys_addr >> mc->bucket_shift;
+    address_offset = phys_addr & (mc->bucket_size - 1);
 
     trace_xen_map_cache(phys_addr);
 
@@ -294,14 +306,14 @@ tryagain:
         return mc->last_entry->vaddr_base + address_offset;
     }
 
-    /* size is always a multiple of MCACHE_BUCKET_SIZE */
+    /* size is always a multiple of mc->bucket_size */
     if (size) {
         cache_size = size + address_offset;
-        if (cache_size % MCACHE_BUCKET_SIZE) {
-            cache_size += MCACHE_BUCKET_SIZE - (cache_size % MCACHE_BUCKET_SIZE);
+        if (cache_size % mc->bucket_size) {
+            cache_size += mc->bucket_size - (cache_size % mc->bucket_size);
         }
     } else {
-        cache_size = MCACHE_BUCKET_SIZE;
+        cache_size = mc->bucket_size;
     }
 
     entry = &mc->entry[address_index % mc->nr_buckets];
@@ -422,7 +434,7 @@ static ram_addr_t xen_ram_addr_from_mapcache_single(MapCache *mc, void *ptr)
         trace_xen_ram_addr_from_mapcache_not_in_cache(ptr);
         raddr = RAM_ADDR_INVALID;
     } else {
-        raddr = (reventry->paddr_index << MCACHE_BUCKET_SHIFT) +
+        raddr = (reventry->paddr_index << mc->bucket_shift) +
              ((unsigned long) ptr - (unsigned long) entry->vaddr_base);
     }
     mapcache_unlock(mc);
@@ -585,8 +597,8 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
     hwaddr address_index, address_offset;
     hwaddr test_bit_size, cache_size = size;
 
-    address_index  = old_phys_addr >> MCACHE_BUCKET_SHIFT;
-    address_offset = old_phys_addr & (MCACHE_BUCKET_SIZE - 1);
+    address_index  = old_phys_addr >> mc->bucket_shift;
+    address_offset = old_phys_addr & (mc->bucket_size - 1);
 
     assert(size);
     /* test_bit_size is always a multiple of XC_PAGE_SIZE */
@@ -595,8 +607,8 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
         test_bit_size += XC_PAGE_SIZE - (test_bit_size % XC_PAGE_SIZE);
     }
     cache_size = size + address_offset;
-    if (cache_size % MCACHE_BUCKET_SIZE) {
-        cache_size += MCACHE_BUCKET_SIZE - (cache_size % MCACHE_BUCKET_SIZE);
+    if (cache_size % mc->bucket_size) {
+        cache_size += mc->bucket_size - (cache_size % mc->bucket_size);
     }
 
     entry = &mc->entry[address_index % mc->nr_buckets];
@@ -609,8 +621,8 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
         return NULL;
     }
 
-    address_index  = new_phys_addr >> MCACHE_BUCKET_SHIFT;
-    address_offset = new_phys_addr & (MCACHE_BUCKET_SIZE - 1);
+    address_index  = new_phys_addr >> mc->bucket_shift;
+    address_offset = new_phys_addr & (mc->bucket_size - 1);
 
     trace_xen_replace_cache_entry_dummy(old_phys_addr, new_phys_addr);
 
-- 
2.40.1

[PATCH v7 2/8] xen: mapcache: Unmap first entries in buckets

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

When invalidating memory ranges, if we happen to hit the first
entry in a bucket we were never unmapping it. This was harmless
for foreign mappings but now that we're looking to reuse the
mapcache for transient grant mappings, we must unmap entries
when invalidated.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
---
 hw/xen/xen-mapcache.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index bc860f4373..ec95445696 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -491,18 +491,23 @@ static void xen_invalidate_map_cache_entry_unlocked(MapCache *mc,
         return;
     }
     entry->lock--;
-    if (entry->lock > 0 || pentry == NULL) {
+    if (entry->lock > 0) {
         return;
     }
 
-    pentry->next = entry->next;
     ram_block_notify_remove(entry->vaddr_base, entry->size, entry->size);
     if (munmap(entry->vaddr_base, entry->size) != 0) {
         perror("unmap fails");
         exit(-1);
     }
+
     g_free(entry->valid_mapping);
-    g_free(entry);
+    if (pentry) {
+        pentry->next = entry->next;
+        g_free(entry);
+    } else {
+        memset(entry, 0, sizeof *entry);
+    }
 }
 
 typedef struct XenMapCacheData {
-- 
2.40.1

[PATCH v7 3/8] xen: Add xen_mr_is_memory()

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

Add xen_mr_is_memory() to abstract away tests for the
xen_memory MR.

No functional changes.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
---
 hw/xen/xen-hvm-common.c | 10 ++++++++--
 include/sysemu/xen.h    |  8 ++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/hw/xen/xen-hvm-common.c b/hw/xen/xen-hvm-common.c
index 2d1b032121..a0a0252da0 100644
--- a/hw/xen/xen-hvm-common.c
+++ b/hw/xen/xen-hvm-common.c
@@ -12,6 +12,12 @@
 
 MemoryRegion xen_memory;
 
+/* Check for xen memory.  */
+bool xen_mr_is_memory(MemoryRegion *mr)
+{
+    return mr == &xen_memory;
+}
+
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr,
                    Error **errp)
 {
@@ -28,7 +34,7 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr,
         return;
     }
 
-    if (mr == &xen_memory) {
+    if (xen_mr_is_memory(mr)) {
         return;
     }
 
@@ -55,7 +61,7 @@ static void xen_set_memory(struct MemoryListener *listener,
 {
     XenIOState *state = container_of(listener, XenIOState, memory_listener);
 
-    if (section->mr == &xen_memory) {
+    if (xen_mr_is_memory(section->mr)) {
         return;
     } else {
         if (add) {
diff --git a/include/sysemu/xen.h b/include/sysemu/xen.h
index 754ec2e6cb..dc72f83bcb 100644
--- a/include/sysemu/xen.h
+++ b/include/sysemu/xen.h
@@ -34,6 +34,8 @@ void xen_hvm_modified_memory(ram_addr_t start, ram_addr_t length);
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
                    struct MemoryRegion *mr, Error **errp);
 
+bool xen_mr_is_memory(MemoryRegion *mr);
+
 #else /* !CONFIG_XEN_IS_POSSIBLE */
 
 #define xen_enabled() 0
@@ -47,6 +49,12 @@ static inline void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
     g_assert_not_reached();
 }
 
+static inline bool xen_mr_is_memory(MemoryRegion *mr)
+{
+    g_assert_not_reached();
+    return false;
+}
+
 #endif /* CONFIG_XEN_IS_POSSIBLE */
 
 #endif
-- 
2.40.1

[PATCH v7 4/8] softmmu: xen: Always pass offset + addr to xen_map_cache

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

Always pass address with offset to xen_map_cache().
This is in preparation for support for grant mappings.

Since this is within a block that checks for offset == 0,
this has no functional changes.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 system/physmem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/system/physmem.c b/system/physmem.c
index 342b7a8fd4..5e6257ef65 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2230,7 +2230,8 @@ static void *qemu_ram_ptr_length(RAMBlock *block, ram_addr_t addr,
          * In that case just map the requested area.
          */
         if (block->offset == 0) {
-            return xen_map_cache(block->mr, addr, len, lock, lock,
+            return xen_map_cache(block->mr, block->offset + addr,
+                                 len, lock, lock,
                                  is_write);
         }
 
-- 
2.40.1

[PATCH v7 5/8] softmmu: Replace check for RAMBlock offset 0 with xen_mr_is_memory

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

For xen, when checking for the first RAM (xen_memory), use
xen_mr_is_memory() rather than checking for a RAMBlock with
offset 0.

All Xen machines create xen_memory first so this has no
functional change for existing machines.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 system/physmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/system/physmem.c b/system/physmem.c
index 5e6257ef65..b7847db1a2 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2229,7 +2229,7 @@ static void *qemu_ram_ptr_length(RAMBlock *block, ram_addr_t addr,
          * because we don't want to map the entire memory in QEMU.
          * In that case just map the requested area.
          */
-        if (block->offset == 0) {
+        if (xen_mr_is_memory(block->mr)) {
             return xen_map_cache(block->mr, block->offset + addr,
                                  len, lock, lock,
                                  is_write);
-- 
2.40.1

[PATCH v7 6/8] xen: mapcache: Pass the ram_addr offset to xen_map_cache()

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

Pass the ram_addr offset to xen_map_cache.
This is in preparation for adding grant mappings that need
to compute the address within the RAMBlock.

No functional changes.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
---
 hw/xen/xen-mapcache.c         | 16 +++++++++++-----
 include/sysemu/xen-mapcache.h |  2 ++
 system/physmem.c              |  9 +++++----
 3 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index ec95445696..a07c47b0b1 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -167,7 +167,8 @@ static void xen_remap_bucket(MapCache *mc,
                              void *vaddr,
                              hwaddr size,
                              hwaddr address_index,
-                             bool dummy)
+                             bool dummy,
+                             ram_addr_t ram_offset)
 {
     uint8_t *vaddr_base;
     xen_pfn_t *pfns;
@@ -266,6 +267,7 @@ static void xen_remap_bucket(MapCache *mc,
 
 static uint8_t *xen_map_cache_unlocked(MapCache *mc,
                                        hwaddr phys_addr, hwaddr size,
+                                       ram_addr_t ram_offset,
                                        uint8_t lock, bool dma, bool is_write)
 {
     MapCacheEntry *entry, *pentry = NULL,
@@ -337,14 +339,16 @@ tryagain:
     if (!entry) {
         entry = g_new0(MapCacheEntry, 1);
         pentry->next = entry;
-        xen_remap_bucket(mc, entry, NULL, cache_size, address_index, dummy);
+        xen_remap_bucket(mc, entry, NULL, cache_size, address_index, dummy,
+                         ram_offset);
     } 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(mc, entry, NULL, cache_size, address_index, dummy);
+            xen_remap_bucket(mc, entry, NULL, cache_size, address_index, dummy,
+                             ram_offset);
         }
     }
 
@@ -391,13 +395,15 @@ tryagain:
 
 uint8_t *xen_map_cache(MemoryRegion *mr,
                        hwaddr phys_addr, hwaddr size,
+                       ram_addr_t ram_addr_offset,
                        uint8_t lock, bool dma,
                        bool is_write)
 {
     uint8_t *p;
 
     mapcache_lock(mapcache);
-    p = xen_map_cache_unlocked(mapcache, phys_addr, size, lock, dma, is_write);
+    p = xen_map_cache_unlocked(mapcache, phys_addr, size, ram_addr_offset,
+                               lock, dma, is_write);
     mapcache_unlock(mapcache);
     return p;
 }
@@ -632,7 +638,7 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
     trace_xen_replace_cache_entry_dummy(old_phys_addr, new_phys_addr);
 
     xen_remap_bucket(mc, entry, entry->vaddr_base,
-                     cache_size, address_index, false);
+                     cache_size, address_index, false, old_phys_addr);
     if (!test_bits(address_offset >> XC_PAGE_SHIFT,
                 test_bit_size >> XC_PAGE_SHIFT,
                 entry->valid_mapping)) {
diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h
index 1ec9e66752..b5e3ea1bc0 100644
--- a/include/sysemu/xen-mapcache.h
+++ b/include/sysemu/xen-mapcache.h
@@ -19,6 +19,7 @@ typedef hwaddr (*phys_offset_to_gaddr_t)(hwaddr phys_offset,
 void xen_map_cache_init(phys_offset_to_gaddr_t f,
                         void *opaque);
 uint8_t *xen_map_cache(MemoryRegion *mr, hwaddr phys_addr, hwaddr size,
+                       ram_addr_t ram_addr_offset,
                        uint8_t lock, bool dma,
                        bool is_write);
 ram_addr_t xen_ram_addr_from_mapcache(void *ptr);
@@ -37,6 +38,7 @@ static inline void xen_map_cache_init(phys_offset_to_gaddr_t f,
 static inline uint8_t *xen_map_cache(MemoryRegion *mr,
                                      hwaddr phys_addr,
                                      hwaddr size,
+                                     ram_addr_t ram_addr_offset,
                                      uint8_t lock,
                                      bool dma,
                                      bool is_write)
diff --git a/system/physmem.c b/system/physmem.c
index b7847db1a2..33d09f7571 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2231,13 +2231,14 @@ static void *qemu_ram_ptr_length(RAMBlock *block, ram_addr_t addr,
          */
         if (xen_mr_is_memory(block->mr)) {
             return xen_map_cache(block->mr, block->offset + addr,
-                                 len, lock, lock,
-                                 is_write);
+                                 len, block->offset,
+                                 lock, lock, is_write);
         }
 
         block->host = xen_map_cache(block->mr, block->offset,
-                                    block->max_length, 1,
-                                    lock, is_write);
+                                    block->max_length,
+                                    block->offset,
+                                    1, lock, is_write);
     }
 
     return ramblock_ptr(block, addr);
-- 
2.40.1

[PATCH v7 7/8] xen: mapcache: Add support for grant mappings

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

Add a second mapcache for grant mappings. The mapcache for
grants needs to work with XC_PAGE_SIZE granularity since
we can't map larger ranges than what has been granted to us.

Like with foreign mappings (xen_memory), machines using grants
are expected to initialize the xen_grants MR and map it
into their address-map accordingly.

CC: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
---
 hw/xen/xen-hvm-common.c         |  12 ++-
 hw/xen/xen-mapcache.c           | 165 +++++++++++++++++++++++++-------
 include/hw/xen/xen-hvm-common.h |   3 +
 include/sysemu/xen.h            |   7 ++
 4 files changed, 150 insertions(+), 37 deletions(-)

diff --git a/hw/xen/xen-hvm-common.c b/hw/xen/xen-hvm-common.c
index a0a0252da0..b8ace1c368 100644
--- a/hw/xen/xen-hvm-common.c
+++ b/hw/xen/xen-hvm-common.c
@@ -10,12 +10,18 @@
 #include "hw/boards.h"
 #include "hw/xen/arch_hvm.h"
 
-MemoryRegion xen_memory;
+MemoryRegion xen_memory, xen_grants;
 
-/* Check for xen memory.  */
+/* Check for any kind of xen memory, foreign mappings or grants.  */
 bool xen_mr_is_memory(MemoryRegion *mr)
 {
-    return mr == &xen_memory;
+    return mr == &xen_memory || mr == &xen_grants;
+}
+
+/* Check specifically for grants.  */
+bool xen_mr_is_grants(MemoryRegion *mr)
+{
+    return mr == &xen_grants;
 }
 
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr,
diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index a07c47b0b1..5f23b0adbe 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -14,6 +14,7 @@
 
 #include <sys/resource.h>
 
+#include "hw/xen/xen-hvm-common.h"
 #include "hw/xen/xen_native.h"
 #include "qemu/bitmap.h"
 
@@ -21,6 +22,8 @@
 #include "sysemu/xen-mapcache.h"
 #include "trace.h"
 
+#include <xenevtchn.h>
+#include <xengnttab.h>
 
 #if HOST_LONG_BITS == 32
 #  define MCACHE_MAX_SIZE     (1UL<<31) /* 2GB Cap */
@@ -41,6 +44,7 @@ typedef struct MapCacheEntry {
     unsigned long *valid_mapping;
     uint32_t lock;
 #define XEN_MAPCACHE_ENTRY_DUMMY (1 << 0)
+#define XEN_MAPCACHE_ENTRY_GRANT (1 << 1)
     uint8_t flags;
     hwaddr size;
     struct MapCacheEntry *next;
@@ -71,6 +75,8 @@ typedef struct MapCache {
 } MapCache;
 
 static MapCache *mapcache;
+static MapCache *mapcache_grants;
+static xengnttab_handle *xen_region_gnttabdev;
 
 static inline void mapcache_lock(MapCache *mc)
 {
@@ -131,6 +137,12 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
     unsigned long max_mcache_size;
     unsigned int bucket_shift;
 
+    xen_region_gnttabdev = xengnttab_open(NULL, 0);
+    if (xen_region_gnttabdev == NULL) {
+        error_report("mapcache: Failed to open gnttab device");
+        exit(EXIT_FAILURE);
+    }
+
     if (HOST_LONG_BITS == 32) {
         bucket_shift = 16;
     } else {
@@ -159,6 +171,15 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
     mapcache = xen_map_cache_init_single(f, opaque,
                                          bucket_shift,
                                          max_mcache_size);
+
+    /*
+     * Grant mappings must use XC_PAGE_SIZE granularity since we can't
+     * map anything beyond the number of pages granted to us.
+     */
+    mapcache_grants = xen_map_cache_init_single(f, opaque,
+                                                XC_PAGE_SHIFT,
+                                                max_mcache_size);
+
     setrlimit(RLIMIT_AS, &rlimit_as);
 }
 
@@ -168,17 +189,24 @@ static void xen_remap_bucket(MapCache *mc,
                              hwaddr size,
                              hwaddr address_index,
                              bool dummy,
+                             bool grant,
+                             bool is_write,
                              ram_addr_t ram_offset)
 {
     uint8_t *vaddr_base;
-    xen_pfn_t *pfns;
-    int *err;
+    g_autofree uint32_t *refs = NULL;
+    g_autofree xen_pfn_t *pfns = NULL;
+    g_autofree int *err;
     unsigned int i;
     hwaddr nb_pfn = size >> XC_PAGE_SHIFT;
 
     trace_xen_remap_bucket(address_index);
 
-    pfns = g_new0(xen_pfn_t, nb_pfn);
+    if (grant) {
+        refs = g_new0(uint32_t, nb_pfn);
+    } else {
+        pfns = g_new0(xen_pfn_t, nb_pfn);
+    }
     err = g_new0(int, nb_pfn);
 
     if (entry->vaddr_base != NULL) {
@@ -207,21 +235,51 @@ static void xen_remap_bucket(MapCache *mc,
     g_free(entry->valid_mapping);
     entry->valid_mapping = NULL;
 
-    for (i = 0; i < nb_pfn; i++) {
-        pfns[i] = (address_index << (mc->bucket_shift - XC_PAGE_SHIFT)) + i;
+    if (grant) {
+        hwaddr grant_base = address_index - (ram_offset >> XC_PAGE_SHIFT);
+
+        for (i = 0; i < nb_pfn; i++) {
+            refs[i] = grant_base + i;
+        }
+    } else {
+        for (i = 0; i < nb_pfn; i++) {
+            pfns[i] = (address_index << (mc->bucket_shift - XC_PAGE_SHIFT)) + i;
+        }
     }
 
-    /*
-     * If the caller has requested the mapping at a specific address use
-     * MAP_FIXED to make sure it's honored.
-     */
+    entry->flags &= ~XEN_MAPCACHE_ENTRY_GRANT;
+
     if (!dummy) {
-        vaddr_base = xenforeignmemory_map2(xen_fmem, xen_domid, vaddr,
-                                           PROT_READ | PROT_WRITE,
-                                           vaddr ? MAP_FIXED : 0,
-                                           nb_pfn, pfns, err);
+        if (grant) {
+            int prot = PROT_READ;
+
+            if (is_write) {
+                prot |= PROT_WRITE;
+            }
+
+            entry->flags |= XEN_MAPCACHE_ENTRY_GRANT;
+            assert(vaddr == NULL);
+            vaddr_base = xengnttab_map_domain_grant_refs(xen_region_gnttabdev,
+                                                         nb_pfn,
+                                                         xen_domid, refs,
+                                                         prot);
+        } else {
+            /*
+             * If the caller has requested the mapping at a specific address use
+             * MAP_FIXED to make sure it's honored.
+             *
+             * We don't yet support upgrading mappings from RO to RW, to handle
+             * models using ordinary address_space_rw(), foreign mappings ignore
+             * is_write and are always mapped RW.
+             */
+            vaddr_base = xenforeignmemory_map2(xen_fmem, xen_domid, vaddr,
+                                               PROT_READ | PROT_WRITE,
+                                               vaddr ? MAP_FIXED : 0,
+                                               nb_pfn, pfns, err);
+        }
         if (vaddr_base == NULL) {
-            perror("xenforeignmemory_map2");
+            perror(grant ? "xengnttab_map_domain_grant_refs"
+                           : "xenforeignmemory_map2");
             exit(-1);
         }
     } else {
@@ -260,15 +318,13 @@ static void xen_remap_bucket(MapCache *mc,
             bitmap_set(entry->valid_mapping, i, 1);
         }
     }
-
-    g_free(pfns);
-    g_free(err);
 }
 
 static uint8_t *xen_map_cache_unlocked(MapCache *mc,
                                        hwaddr phys_addr, hwaddr size,
                                        ram_addr_t ram_offset,
-                                       uint8_t lock, bool dma, bool is_write)
+                                       uint8_t lock, bool dma,
+                                       bool grant, bool is_write)
 {
     MapCacheEntry *entry, *pentry = NULL,
                   *free_entry = NULL, *free_pentry = NULL;
@@ -340,7 +396,7 @@ tryagain:
         entry = g_new0(MapCacheEntry, 1);
         pentry->next = entry;
         xen_remap_bucket(mc, entry, NULL, cache_size, address_index, dummy,
-                         ram_offset);
+                         grant, is_write, ram_offset);
     } else if (!entry->lock) {
         if (!entry->vaddr_base || entry->paddr_index != address_index ||
                 entry->size != cache_size ||
@@ -348,7 +404,7 @@ tryagain:
                     test_bit_size >> XC_PAGE_SHIFT,
                     entry->valid_mapping)) {
             xen_remap_bucket(mc, entry, NULL, cache_size, address_index, dummy,
-                             ram_offset);
+                             grant, is_write, ram_offset);
         }
     }
 
@@ -399,12 +455,26 @@ uint8_t *xen_map_cache(MemoryRegion *mr,
                        uint8_t lock, bool dma,
                        bool is_write)
 {
+    bool grant = xen_mr_is_grants(mr);
+    MapCache *mc = grant ? mapcache_grants : mapcache;
     uint8_t *p;
 
-    mapcache_lock(mapcache);
-    p = xen_map_cache_unlocked(mapcache, phys_addr, size, ram_addr_offset,
-                               lock, dma, is_write);
-    mapcache_unlock(mapcache);
+    if (grant && !lock) {
+        /*
+         * Grants are only supported via address_space_map(). Anything
+         * else is considered a user/guest error.
+         *
+         * QEMU generally doesn't expect these mappings to ever fail, so
+         * if this happens we report an error message and abort().
+         */
+        error_report("Tried to access a grant reference without mapping it.");
+        abort();
+    }
+
+    mapcache_lock(mc);
+    p = xen_map_cache_unlocked(mc, phys_addr, size, ram_addr_offset,
+                               lock, dma, grant, is_write);
+    mapcache_unlock(mc);
     return p;
 }
 
@@ -449,7 +519,14 @@ static ram_addr_t xen_ram_addr_from_mapcache_single(MapCache *mc, void *ptr)
 
 ram_addr_t xen_ram_addr_from_mapcache(void *ptr)
 {
-    return xen_ram_addr_from_mapcache_single(mapcache, ptr);
+    ram_addr_t addr;
+
+    addr = xen_ram_addr_from_mapcache_single(mapcache, ptr);
+    if (addr == RAM_ADDR_INVALID) {
+        addr = xen_ram_addr_from_mapcache_single(mapcache_grants, ptr);
+    }
+
+    return addr;
 }
 
 static void xen_invalidate_map_cache_entry_unlocked(MapCache *mc,
@@ -460,6 +537,7 @@ static void xen_invalidate_map_cache_entry_unlocked(MapCache *mc,
     hwaddr paddr_index;
     hwaddr size;
     int found = 0;
+    int rc;
 
     QTAILQ_FOREACH(reventry, &mc->locked_entries, next) {
         if (reventry->vaddr_req == buffer) {
@@ -502,7 +580,14 @@ static void xen_invalidate_map_cache_entry_unlocked(MapCache *mc,
     }
 
     ram_block_notify_remove(entry->vaddr_base, entry->size, entry->size);
-    if (munmap(entry->vaddr_base, entry->size) != 0) {
+    if (entry->flags & XEN_MAPCACHE_ENTRY_GRANT) {
+        rc = xengnttab_unmap(xen_region_gnttabdev, entry->vaddr_base,
+                             entry->size >> mc->bucket_shift);
+    } else {
+        rc = munmap(entry->vaddr_base, entry->size);
+    }
+
+    if (rc) {
         perror("unmap fails");
         exit(-1);
     }
@@ -521,14 +606,24 @@ typedef struct XenMapCacheData {
     uint8_t *buffer;
 } XenMapCacheData;
 
+static void xen_invalidate_map_cache_entry_single(MapCache *mc, uint8_t *buffer)
+{
+    mapcache_lock(mc);
+    xen_invalidate_map_cache_entry_unlocked(mc, buffer);
+    mapcache_unlock(mc);
+}
+
+static void xen_invalidate_map_cache_entry_all(uint8_t *buffer)
+{
+    xen_invalidate_map_cache_entry_single(mapcache, buffer);
+    xen_invalidate_map_cache_entry_single(mapcache_grants, buffer);
+}
+
 static void xen_invalidate_map_cache_entry_bh(void *opaque)
 {
     XenMapCacheData *data = opaque;
 
-    mapcache_lock(mapcache);
-    xen_invalidate_map_cache_entry_unlocked(mapcache, data->buffer);
-    mapcache_unlock(mapcache);
-
+    xen_invalidate_map_cache_entry_all(data->buffer);
     aio_co_wake(data->co);
 }
 
@@ -543,9 +638,7 @@ void coroutine_mixed_fn xen_invalidate_map_cache_entry(uint8_t *buffer)
                                 xen_invalidate_map_cache_entry_bh, &data);
         qemu_coroutine_yield();
     } else {
-        mapcache_lock(mapcache);
-        xen_invalidate_map_cache_entry_unlocked(mapcache, buffer);
-        mapcache_unlock(mapcache);
+        xen_invalidate_map_cache_entry_all(buffer);
     }
 }
 
@@ -597,6 +690,7 @@ void xen_invalidate_map_cache(void)
     bdrv_drain_all();
 
     xen_invalidate_map_cache_single(mapcache);
+    xen_invalidate_map_cache_single(mapcache_grants);
 }
 
 static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
@@ -632,13 +726,16 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
         return NULL;
     }
 
+    assert((entry->flags & XEN_MAPCACHE_ENTRY_GRANT) == 0);
+
     address_index  = new_phys_addr >> mc->bucket_shift;
     address_offset = new_phys_addr & (mc->bucket_size - 1);
 
     trace_xen_replace_cache_entry_dummy(old_phys_addr, new_phys_addr);
 
     xen_remap_bucket(mc, entry, entry->vaddr_base,
-                     cache_size, address_index, false, old_phys_addr);
+                     cache_size, address_index, false,
+                     false, false, old_phys_addr);
     if (!test_bits(address_offset >> XC_PAGE_SHIFT,
                 test_bit_size >> XC_PAGE_SHIFT,
                 entry->valid_mapping)) {
diff --git a/include/hw/xen/xen-hvm-common.h b/include/hw/xen/xen-hvm-common.h
index 65a51aac2e..3d796235dc 100644
--- a/include/hw/xen/xen-hvm-common.h
+++ b/include/hw/xen/xen-hvm-common.h
@@ -16,6 +16,7 @@
 #include <xen/hvm/ioreq.h>
 
 extern MemoryRegion xen_memory;
+extern MemoryRegion xen_grants;
 extern MemoryListener xen_io_listener;
 extern DeviceListener xen_device_listener;
 
@@ -29,6 +30,8 @@ extern DeviceListener xen_device_listener;
     do { } while (0)
 #endif
 
+#define XEN_GRANT_ADDR_OFF (1ULL << 63)
+
 static inline uint32_t xen_vcpu_eport(shared_iopage_t *shared_page, int i)
 {
     return shared_page->vcpu_ioreq[i].vp_eport;
diff --git a/include/sysemu/xen.h b/include/sysemu/xen.h
index dc72f83bcb..19dccf4d71 100644
--- a/include/sysemu/xen.h
+++ b/include/sysemu/xen.h
@@ -35,6 +35,7 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
                    struct MemoryRegion *mr, Error **errp);
 
 bool xen_mr_is_memory(MemoryRegion *mr);
+bool xen_mr_is_grants(MemoryRegion *mr);
 
 #else /* !CONFIG_XEN_IS_POSSIBLE */
 
@@ -55,6 +56,12 @@ static inline bool xen_mr_is_memory(MemoryRegion *mr)
     return false;
 }
 
+static inline bool xen_mr_is_grants(MemoryRegion *mr)
+{
+    g_assert_not_reached();
+    return false;
+}
+
 #endif /* CONFIG_XEN_IS_POSSIBLE */
 
 #endif
-- 
2.40.1

[PATCH v7 8/8] hw/arm: xen: Enable use of grant mappings

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
 hw/arm/xen_arm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/arm/xen_arm.c b/hw/arm/xen_arm.c
index 15fa7dfa84..6fad829ede 100644
--- a/hw/arm/xen_arm.c
+++ b/hw/arm/xen_arm.c
@@ -125,6 +125,11 @@ static void xen_init_ram(MachineState *machine)
                                  GUEST_RAM1_BASE, ram_size[1]);
         memory_region_add_subregion(sysmem, GUEST_RAM1_BASE, &ram_hi);
     }
+
+    /* Setup support for grants.  */
+    memory_region_init_ram(&xen_grants, NULL, "xen.grants", block_len,
+                           &error_fatal);
+    memory_region_add_subregion(sysmem, XEN_GRANT_ADDR_OFF, &xen_grants);
 }
 
 void arch_handle_ioreq(XenIOState *state, ioreq_t *req)
-- 
2.40.1

Re: [PATCH v7 8/8] hw/arm: xen: Enable use of grant mappings

[Philippe Mathieu-Daudé]

On 24/5/24 12:51, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
> ---
>   hw/arm/xen_arm.c | 5 +++++
>   1 file changed, 5 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH v7 6/8] xen: mapcache: Pass the ram_addr offset to xen_map_cache()

[Philippe Mathieu-Daudé]

On 24/5/24 12:51, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>
> 
> Pass the ram_addr offset to xen_map_cache.
> This is in preparation for adding grant mappings that need
> to compute the address within the RAMBlock.
> 
> No functional changes.
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> ---
>   hw/xen/xen-mapcache.c         | 16 +++++++++++-----
>   include/sysemu/xen-mapcache.h |  2 ++
>   system/physmem.c              |  9 +++++----
>   3 files changed, 18 insertions(+), 9 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH v7 3/8] xen: Add xen_mr_is_memory()

[Philippe Mathieu-Daudé]

Hi Edgar,

On 24/5/24 12:51, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>
> 
> Add xen_mr_is_memory() to abstract away tests for the
> xen_memory MR.
> 
> No functional changes.
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> Acked-by: David Hildenbrand <david@redhat.com>
> ---
>   hw/xen/xen-hvm-common.c | 10 ++++++++--
>   include/sysemu/xen.h    |  8 ++++++++
>   2 files changed, 16 insertions(+), 2 deletions(-)

To consolidate we could add:

   static MemoryRegion xen_memory;

   MemoryRegion *xen_mr_memory_init(uint64_t block_len)
   {
      assert(!xen_memory.size);
      memory_region_init_ram(&xen_memory, NULL, "xen.ram", block_len, 
&error_fatal);
      return &xen_memory;
   }

and remove the extern declaration.

> diff --git a/include/sysemu/xen.h b/include/sysemu/xen.h
> index 754ec2e6cb..dc72f83bcb 100644
> --- a/include/sysemu/xen.h
> +++ b/include/sysemu/xen.h
> @@ -34,6 +34,8 @@ void xen_hvm_modified_memory(ram_addr_t start, ram_addr_t length);
>   void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
>                      struct MemoryRegion *mr, Error **errp);
>   
> +bool xen_mr_is_memory(MemoryRegion *mr);
> +
>   #else /* !CONFIG_XEN_IS_POSSIBLE */
>   
>   #define xen_enabled() 0
> @@ -47,6 +49,12 @@ static inline void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
>       g_assert_not_reached();
>   }
>   
> +static inline bool xen_mr_is_memory(MemoryRegion *mr)
> +{
> +    g_assert_not_reached();
> +    return false;

No need for the stub, just always declare xen_mr_is_memory() ...
> +}
> +
>   #endif /* CONFIG_XEN_IS_POSSIBLE */

... here.

>   #endif

Removing the stub:
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH v7 3/8] xen: Add xen_mr_is_memory()

[Edgar E. Iglesias]

[-- Attachment #1: Type: text/plain, Size: 2274 bytes --]

On Mon, May 27, 2024 at 6:25 PM Philippe Mathieu-Daudé <philmd@linaro.org>
wrote:

> Hi Edgar,
>
> On 24/5/24 12:51, Edgar E. Iglesias wrote:
> > From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>
> >
> > Add xen_mr_is_memory() to abstract away tests for the
> > xen_memory MR.
> >
> > No functional changes.
> >
> > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
> > Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> > Acked-by: David Hildenbrand <david@redhat.com>
> > ---
> >   hw/xen/xen-hvm-common.c | 10 ++++++++--
> >   include/sysemu/xen.h    |  8 ++++++++
> >   2 files changed, 16 insertions(+), 2 deletions(-)
>
> To consolidate we could add:
>
>    static MemoryRegion xen_memory;
>
>    MemoryRegion *xen_mr_memory_init(uint64_t block_len)
>    {
>       assert(!xen_memory.size);
>       memory_region_init_ram(&xen_memory, NULL, "xen.ram", block_len,
> &error_fatal);
>       return &xen_memory;
>    }
>
> and remove the extern declaration.
>

Thanks,

We have a future patch series in the workings that will add a PVH machine
for x86, I'll keep this in mind for then!


>
> > diff --git a/include/sysemu/xen.h b/include/sysemu/xen.h
> > index 754ec2e6cb..dc72f83bcb 100644
> > --- a/include/sysemu/xen.h
> > +++ b/include/sysemu/xen.h
> > @@ -34,6 +34,8 @@ void xen_hvm_modified_memory(ram_addr_t start,
> ram_addr_t length);
> >   void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
> >                      struct MemoryRegion *mr, Error **errp);
> >
> > +bool xen_mr_is_memory(MemoryRegion *mr);
> > +
> >   #else /* !CONFIG_XEN_IS_POSSIBLE */
> >
> >   #define xen_enabled() 0
> > @@ -47,6 +49,12 @@ static inline void xen_ram_alloc(ram_addr_t ram_addr,
> ram_addr_t size,
> >       g_assert_not_reached();
> >   }
> >
> > +static inline bool xen_mr_is_memory(MemoryRegion *mr)
> > +{
> > +    g_assert_not_reached();
> > +    return false;
>
> No need for the stub, just always declare xen_mr_is_memory() ...
> > +}
> > +
> >   #endif /* CONFIG_XEN_IS_POSSIBLE */
>
> ... here.
>
> >   #endif
>
> Removing the stub:
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>
>
Thanks Philippe, will remove the stubs in v8.

Cheers,
Edgar

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