Re: [QEMU][PATCH v3 3/7] softmmu: let qemu_map_ram_ptr() use qemu_ram_ptr_length()

["Alex Bennée" <alex.bennee@linaro.org>]

Vikram Garhwal <vikram.garhwal@amd.com> writes:

> From: Juergen Gross <jgross@suse.com>
>
> qemu_map_ram_ptr() and qemu_ram_ptr_length() share quite some code, so
> modify qemu_ram_ptr_length() a little bit and use it for
> qemu_map_ram_ptr(), too.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> ---
>  system/physmem.c | 56 ++++++++++++++++++++----------------------------
>  1 file changed, 23 insertions(+), 33 deletions(-)
>
<snip>
> -
> -/* Return a host pointer to guest's ram. Similar to qemu_map_ram_ptr
> - * but takes a size argument.
> +/*
> + * Return a host pointer to guest's ram.
>   *
>   * Called within RCU critical section.
>   */

If you end up re-spinning it would be nice to kdoc this function and at
least call out size as a return by ref and optional. 

>  static void *qemu_ram_ptr_length(RAMBlock *block, ram_addr_t addr,
>                                   hwaddr *size, bool lock)
>  {
> -    if (*size == 0) {
> +    hwaddr len = 0;
> +
> +    if (size && *size == 0) {
>          return NULL;
>      }
>  
> @@ -2207,7 +2181,10 @@ static void *qemu_ram_ptr_length(RAMBlock *block, ram_addr_t addr,
>          block = qemu_get_ram_block(addr);
>          addr -= block->offset;
>      }
> -    *size = MIN(*size, block->max_length - addr);
> +    if (size) {
> +        *size = MIN(*size, block->max_length - addr);
> +        len = *size;
> +    }
>  
>      if (xen_enabled() && block->host == NULL) {
>          /* We need to check if the requested address is in the RAM
> @@ -2215,7 +2192,7 @@ 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(addr, *size, lock, lock);
> +            return xen_map_cache(addr, len, lock, lock);

I did wonder if len == 0 will confuse things but it seems xen_map_cache
will default to XC_PAGE_SIZE in that case.

Anyway:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro