From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Olaf Hering <olaf@aepfle.de>
Date: Wed, 5 Feb 2020 19:26:03 +0100
Subject: [PATCH] xen/mapcache: introduce xen_replace_cache_entry()

This new call is trying to update a requested map cache entry
according to the changes in the physmap. The call is searching
for the entry, unmaps it and maps again at the same place using
a new guest address. If the mapping is dummy this call will
make it real.

This function makes use of a new xenforeignmemory_map2() call
with an extended interface that was recently introduced in
libxenforeignmemory [1].

[1] https://www.mail-archive.com/xen-devel@lists.xen.org/msg113007.html

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
(cherry picked from commit 5ba3d7564593c55292056ef5af84d50b55ebcf0e)
(adjusted to use xenforeignmemory_map instead of xenforeignmemory_map2)
[BSC#1160024]
---
 include/sysemu/xen-mapcache.h | 11 ++++-
 xen-mapcache.c                | 79 ++++++++++++++++++++++++++++++++---
 2 files changed, 84 insertions(+), 6 deletions(-)

diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h
index 01daaad00c..bd4d49e0a4 100644
--- a/include/sysemu/xen-mapcache.h
+++ b/include/sysemu/xen-mapcache.h
@@ -21,7 +21,9 @@ uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size,
 ram_addr_t xen_ram_addr_from_mapcache(void *ptr);
 void xen_invalidate_map_cache_entry(uint8_t *buffer);
 void xen_invalidate_map_cache(void);
-
+uint8_t *xen_replace_cache_entry(hwaddr old_phys_addr,
+                                 hwaddr new_phys_addr,
+                                 hwaddr size);
 #else
 
 static inline void xen_map_cache_init(phys_offset_to_gaddr_t f,
@@ -50,6 +52,13 @@ static inline void xen_invalidate_map_cache(void)
 {
 }
 
+static inline uint8_t *xen_replace_cache_entry(hwaddr old_phys_addr,
+                                               hwaddr new_phys_addr,
+                                               hwaddr size)
+{
+    abort();
+}
+
 #endif
 
 #endif /* XEN_MAPCACHE_H */
diff --git a/xen-mapcache.c b/xen-mapcache.c
index f8e4a8b82e..6ef8be6b69 100644
--- a/xen-mapcache.c
+++ b/xen-mapcache.c
@@ -151,6 +151,7 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
 }
 
 static void xen_remap_bucket(MapCacheEntry *entry,
+                             void *vaddr,
                              hwaddr size,
                              hwaddr address_index,
                              bool dummy)
@@ -167,7 +168,9 @@ static void xen_remap_bucket(MapCacheEntry *entry,
     err = g_malloc0(nb_pfn * sizeof (int));
 
     if (entry->vaddr_base != NULL) {
-        ram_block_notify_remove(entry->vaddr_base, entry->size);
+        if (!(entry->flags & XEN_MAPCACHE_ENTRY_DUMMY)) {
+            ram_block_notify_remove(entry->vaddr_base, entry->size);
+        }
         if (munmap(entry->vaddr_base, entry->size) != 0) {
             perror("unmap fails");
             exit(-1);
@@ -193,7 +196,7 @@ static void xen_remap_bucket(MapCacheEntry *entry,
          * 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,
+        vaddr_base = mmap(vaddr, size, PROT_READ | PROT_WRITE,
                           MAP_ANON | MAP_SHARED, -1, 0);
         if (vaddr_base == NULL) {
             perror("mmap");
@@ -201,6 +204,10 @@ static void xen_remap_bucket(MapCacheEntry *entry,
         }
     }
 
+    if (!(entry->flags & XEN_MAPCACHE_ENTRY_DUMMY)) {
+        ram_block_notify_add(vaddr_base, size);
+    }
+
     entry->vaddr_base = vaddr_base;
     entry->paddr_index = address_index;
     entry->size = size;
@@ -213,7 +220,6 @@ static void xen_remap_bucket(MapCacheEntry *entry,
         entry->flags &= ~(XEN_MAPCACHE_ENTRY_DUMMY);
     }
 
-    ram_block_notify_add(entry->vaddr_base, entry->size);
     bitmap_zero(entry->valid_mapping, nb_pfn);
     for (i = 0; i < nb_pfn; i++) {
         if (!err[i]) {
@@ -286,14 +292,14 @@ tryagain:
     if (!entry) {
         entry = g_malloc0(sizeof (MapCacheEntry));
         pentry->next = entry;
-        xen_remap_bucket(entry, cache_size, address_index, dummy);
+        xen_remap_bucket(entry, NULL, 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, dummy);
+            xen_remap_bucket(entry, NULL, cache_size, address_index, dummy);
         }
     }
 
@@ -490,3 +496,66 @@ void xen_invalidate_map_cache(void)
 
     mapcache_unlock();
 }
+
+static uint8_t *xen_replace_cache_entry_unlocked(hwaddr old_phys_addr,
+                                                 hwaddr new_phys_addr,
+                                                 hwaddr size)
+{
+    MapCacheEntry *entry;
+    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);
+
+    assert(size);
+    /* test_bit_size is always a multiple of XC_PAGE_SIZE */
+    test_bit_size = size + (old_phys_addr & (XC_PAGE_SIZE - 1));
+    if (test_bit_size % XC_PAGE_SIZE) {
+        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);
+    }
+
+    entry = &mapcache->entry[address_index % mapcache->nr_buckets];
+    while (entry && !(entry->paddr_index == address_index &&
+                      entry->size == cache_size)) {
+        entry = entry->next;
+    }
+    if (!entry) {
+        DPRINTF("Trying to update an entry for %lx " \
+                "that is not in the mapcache!\n", old_phys_addr);
+        return NULL;
+    }
+
+    address_index  = new_phys_addr >> MCACHE_BUCKET_SHIFT;
+    address_offset = new_phys_addr & (MCACHE_BUCKET_SIZE - 1);
+
+    fprintf(stderr, "Replacing a dummy mapcache entry for %lx with %lx\n",
+            old_phys_addr, new_phys_addr);
+
+    xen_remap_bucket(entry, entry->vaddr_base,
+                     cache_size, address_index, false);
+    if (!test_bits(address_offset >> XC_PAGE_SHIFT,
+                test_bit_size >> XC_PAGE_SHIFT,
+                entry->valid_mapping)) {
+        DPRINTF("Unable to update a mapcache entry for %lx!\n", old_phys_addr);
+        return NULL;
+    }
+
+    return entry->vaddr_base + address_offset;
+}
+
+uint8_t *xen_replace_cache_entry(hwaddr old_phys_addr,
+                                 hwaddr new_phys_addr,
+                                 hwaddr size)
+{
+    uint8_t *p;
+
+    mapcache_lock();
+    p = xen_replace_cache_entry_unlocked(old_phys_addr, new_phys_addr, size);
+    mapcache_unlock();
+    return p;
+}
