Re: [Qemu-devel] [PATCH] exec: revert MemoryRegionCache

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Apr 03, 2017 at 03:39:01PM +0200, Paolo Bonzini wrote:
> MemoryRegionCache did not know about virtio support for IOMMUs (because the
> two features were developed at the same time).  Revert MemoryRegionCache
> to "normal" address_space_* operations for 2.9, as it is simpler than
> undoing the virtio patches.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

who's merging this? Me?

> ---
>  exec.c                | 64 +++++++++------------------------------------------
>  include/exec/memory.h | 10 ++++----
>  2 files changed, 15 insertions(+), 59 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index e57a8a2..c97ef4a 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -3236,75 +3236,33 @@ int64_t address_space_cache_init(MemoryRegionCache *cache,
>                                   hwaddr len,
>                                   bool is_write)
>  {
> -    hwaddr l, xlat;
> -    MemoryRegion *mr;
> -    void *ptr;
> -
> -    assert(len > 0);
> -
> -    l = len;
> -    mr = address_space_translate(as, addr, &xlat, &l, is_write);
> -    if (!memory_access_is_direct(mr, is_write)) {
> -        return -EINVAL;
> -    }
> -
> -    l = address_space_extend_translation(as, addr, len, mr, xlat, l, is_write);
> -    ptr = qemu_ram_ptr_length(mr->ram_block, xlat, &l);
> -
> -    cache->xlat = xlat;
> -    cache->is_write = is_write;
> -    cache->mr = mr;
> -    cache->ptr = ptr;
> -    cache->len = l;
> -    memory_region_ref(cache->mr);
> -
> -    return l;
> +    cache->len = len;
> +    cache->as = as;
> +    cache->xlat = addr;
> +    return len;
>  }
>  
>  void address_space_cache_invalidate(MemoryRegionCache *cache,
>                                      hwaddr addr,
>                                      hwaddr access_len)
>  {
> -    assert(cache->is_write);
> -    invalidate_and_set_dirty(cache->mr, addr + cache->xlat, access_len);
>  }
>  
>  void address_space_cache_destroy(MemoryRegionCache *cache)
>  {
> -    if (!cache->mr) {
> -        return;
> -    }
> -
> -    if (xen_enabled()) {
> -        xen_invalidate_map_cache_entry(cache->ptr);
> -    }
> -    memory_region_unref(cache->mr);
> -    cache->mr = NULL;
> -}
> -
> -/* Called from RCU critical section.  This function has the same
> - * semantics as address_space_translate, but it only works on a
> - * predefined range of a MemoryRegion that was mapped with
> - * address_space_cache_init.
> - */
> -static inline MemoryRegion *address_space_translate_cached(
> -    MemoryRegionCache *cache, hwaddr addr, hwaddr *xlat,
> -    hwaddr *plen, bool is_write)
> -{
> -    assert(addr < cache->len && *plen <= cache->len - addr);
> -    *xlat = addr + cache->xlat;
> -    return cache->mr;
> +    cache->as = NULL;
>  }
>  
>  #define ARG1_DECL                MemoryRegionCache *cache
>  #define ARG1                     cache
>  #define SUFFIX                   _cached
> -#define TRANSLATE(...)           address_space_translate_cached(cache, __VA_ARGS__)
> +#define TRANSLATE(addr, ...)     \
> +    address_space_translate(cache->as, cache->xlat + (addr), __VA_ARGS__)
>  #define IS_DIRECT(mr, is_write)  true
> -#define MAP_RAM(mr, ofs)         (cache->ptr + (ofs - cache->xlat))
> -#define INVALIDATE(mr, ofs, len) ((void)0)
> -#define RCU_READ_LOCK()          ((void)0)
> -#define RCU_READ_UNLOCK()        ((void)0)
> +#define MAP_RAM(mr, ofs)         qemu_map_ram_ptr((mr)->ram_block, ofs)
> +#define INVALIDATE(mr, ofs, len) invalidate_and_set_dirty(mr, ofs, len)
> +#define RCU_READ_LOCK()          rcu_read_lock()
> +#define RCU_READ_UNLOCK()        rcu_read_unlock()
>  #include "memory_ldst.inc.c"
>  
>  /* virtual memory access for debug (includes writing to ROM) */
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index e39256a..f20b191 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -1426,13 +1426,11 @@ void stq_be_phys(AddressSpace *as, hwaddr addr, uint64_t val);
>  
>  struct MemoryRegionCache {
>      hwaddr xlat;
> -    void *ptr;
>      hwaddr len;
> -    MemoryRegion *mr;
> -    bool is_write;
> +    AddressSpace *as;
>  };
>  
> -#define MEMORY_REGION_CACHE_INVALID ((MemoryRegionCache) { .mr = NULL })
> +#define MEMORY_REGION_CACHE_INVALID ((MemoryRegionCache) { .as = NULL })
>  
>  /* address_space_cache_init: prepare for repeated access to a physical
>   * memory region
> @@ -1688,7 +1686,7 @@ address_space_read_cached(MemoryRegionCache *cache, hwaddr addr,
>                            void *buf, int len)
>  {
>      assert(addr < cache->len && len <= cache->len - addr);
> -    memcpy(buf, cache->ptr + addr, len);
> +    address_space_read(cache->as, cache->xlat + addr, MEMTXATTRS_UNSPECIFIED, buf, len);
>  }
>  
>  /**
> @@ -1704,7 +1702,7 @@ address_space_write_cached(MemoryRegionCache *cache, hwaddr addr,
>                             void *buf, int len)
>  {
>      assert(addr < cache->len && len <= cache->len - addr);
> -    memcpy(cache->ptr + addr, buf, len);
> +    address_space_write(cache->as, cache->xlat + addr, MEMTXATTRS_UNSPECIFIED, buf, len);
>  }
>  
>  #endif
> -- 
> 2.9.3