Re: [QEMU][PATCHv2 4/8] softmmu: let qemu_map_ram_ptr() use qemu_ram_ptr_length()

[Stefano Stabellini]

On Wed, 25 Oct 2023, Vikram Garhwal wrote:
> 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 | 58 +++++++++++++++++++-----------------------------
>  1 file changed, 23 insertions(+), 35 deletions(-)
> 
> diff --git a/system/physmem.c b/system/physmem.c
> index 7a7f95b8b9..667a695078 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -2163,38 +2163,8 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
>  }
>  #endif /* !_WIN32 */
>  
> -/* Return a host pointer to ram allocated with qemu_ram_alloc.
> - * This should not be used for general purpose DMA.  Use address_space_map
> - * or address_space_rw instead. For local memory (e.g. video ram) that the
> - * device owns, use memory_region_get_ram_ptr.
> - *
> - * Called within RCU critical section.
> - */
> -void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr)
> -{
> -    RAMBlock *block = ram_block;
> -
> -    if (block == NULL) {
> -        block = qemu_get_ram_block(addr);
> -        addr -= block->offset;
> -    }
> -
> -    if (xen_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 until the end of the page.
> -         */
> -        if (block->offset == 0) {
> -            return xen_map_cache(addr, 0, 0, false);
> -        }
> -
> -        block->host = xen_map_cache(block->offset, block->max_length, 1, 
> false);
> -    }
> -    return ramblock_ptr(block, addr);
> -}
> -
> -/* 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.
>   */
> @@ -2202,7 +2172,9 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, 
> ram_addr_t addr,
>                                   hwaddr *size, bool lock)
>  {
>      RAMBlock *block = ram_block;
> -    if (*size == 0) {
> +    hwaddr len = 0;
> +
> +    if (size && *size == 0) {
>          return NULL;
>      }
>  
> @@ -2210,7 +2182,10 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_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
> @@ -2218,7 +2193,7 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_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);
>          }
>  
>          block->host = xen_map_cache(block->offset, block->max_length, 1, 
> lock);
> @@ -2227,6 +2202,19 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, 
> ram_addr_t addr,
>      return ramblock_ptr(block, addr);
>  }
>  
> +/*
> + * Return a host pointer to ram allocated with qemu_ram_alloc.
> + * This should not be used for general purpose DMA.  Use address_space_map
> + * or address_space_rw instead. For local memory (e.g. video ram) that the
> + * device owns, use memory_region_get_ram_ptr.
> + *
> + * Called within RCU critical section.
> + */
> +void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr)
> +{
> +    return qemu_ram_ptr_length(ram_block, addr, NULL, false);
> +}
> +
>  /* Return the offset of a hostpointer within a ramblock */
>  ram_addr_t qemu_ram_block_host_offset(RAMBlock *rb, void *host)
>  {
> -- 
> 2.17.1
>