Re: [PATCH v1 3/5] physmem: xen: Conditionalize use of the mapcache

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 4 Mar 2026, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxx>
> 
> Conditionalize use of the mapcache. This is in preparation
> to optionally disable the mapcache at runtime.
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>
> ---
>  system/physmem.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/system/physmem.c b/system/physmem.c
> index e5ff26acec..64e6d50f8f 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -578,7 +578,8 @@ MemoryRegion *flatview_translate(FlatView *fv, hwaddr 
> addr, hwaddr *xlat,
>                                      is_write, true, &as, attrs);
>      mr = section.mr;
>  
> -    if (xen_enabled() && memory_access_is_direct(mr, is_write, attrs)) {
> +    if (xen_map_cache_enabled() &&
> +        memory_access_is_direct(mr, is_write, attrs)) {
>          hwaddr page = ((addr & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE) - addr;
>          *plen = MIN(page, *plen);
>      }

All the other changes make sense. For this one, the code inside the if
check is not strictly related to the mapcache. Are you sure it should be
changed?


> @@ -2577,7 +2578,7 @@ static void reclaim_ramblock(RAMBlock *block)
>  {
>      if (block->flags & RAM_PREALLOC) {
>          ;
> -    } else if (xen_enabled()) {
> +    } else if (xen_map_cache_enabled()) {
>          xen_invalidate_map_cache_entry(block->host);
>  #if !defined(_WIN32) && !defined(EMSCRIPTEN)
>      } else if (block->fd >= 0) {
> @@ -2736,7 +2737,7 @@ static void *qemu_ram_ptr_length(RAMBlock *block, 
> ram_addr_t addr,
>          len = *size;
>      }
>  
> -    if (xen_enabled() && block->host == NULL) {
> +    if (xen_map_cache_enabled() && block->host == NULL) {
>          /* We need to check if the requested address is in the RAM
>           * because we don't want to map the entire memory in QEMU.
>           * In that case just map the requested area.
> @@ -2785,7 +2786,7 @@ RAMBlock *qemu_ram_block_from_host(void *ptr, bool 
> round_offset,
>      RAMBlock *block;
>      uint8_t *host = ptr;
>  
> -    if (xen_enabled()) {
> +    if (xen_map_cache_enabled()) {
>          ram_addr_t ram_addr;
>          RCU_READ_LOCK_GUARD();
>          ram_addr = xen_ram_addr_from_mapcache(ptr);
> @@ -3787,7 +3788,7 @@ void address_space_unmap(AddressSpace *as, void 
> *buffer, hwaddr len,
>          if (is_write) {
>              invalidate_and_set_dirty(mr, addr1, access_len);
>          }
> -        if (xen_enabled()) {
> +        if (xen_map_cache_enabled()) {
>              xen_invalidate_map_cache_entry(buffer);
>          }
>          memory_region_unref(mr);
> @@ -3898,7 +3899,7 @@ void address_space_cache_destroy(MemoryRegionCache 
> *cache)
>          return;
>      }
>  
> -    if (xen_enabled()) {
> +    if (xen_map_cache_enabled()) {
>          xen_invalidate_map_cache_entry(cache->ptr);
>      }
>      memory_region_unref(cache->mrs.mr);
> -- 
> 2.43.0
>