Re: [PATCH for-5.0 v2 3/3] exec: Fix for qemu_ram_resize() callback

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/3/20 12:18 PM, Shameer Kolothum wrote:
> From: David Hildenbrand <david@redhat.com>
> 
> Summarizing the issue:
> 1. Memory regions contain ram blocks with a different size,  if the
>     size is  not properly aligned. While memory regions can have an
>     unaligned size, ram blocks can't. This is true when creating
>     resizable memory region with  an unaligned size.
> 2. When resizing a ram block/memory region, the size of the memory
>     region  is set to the aligned size. The callback is called with
>     the aligned size. The unaligned piece is lost.
> 
> Because of the above, if ACPI blob length modifications happens
> after the initial virt_acpi_build() call, and the changed blob
> length is within the PAGE size boundary, then the revised size
> is not seen by the firmware on Guest reboot.
> 
> Hence make sure callback is called if memory region size is changed,
> irrespective of aligned or not.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> [Shameer: added commit log]
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
> Please find previous discussion here,
> https://patchwork.kernel.org/patch/11432375/#23216751
> ---
>   exec.c | 16 ++++++++++++++--
>   1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index de9d949902..2874bb5088 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2074,11 +2074,23 @@ static int memory_try_enable_merging(void *addr, size_t len)
>    */
>   int qemu_ram_resize(RAMBlock *block, ram_addr_t newsize, Error **errp)
>   {
> +    const ram_addr_t unaligned_size = newsize;
> +
>       assert(block);
>   
>       newsize = HOST_PAGE_ALIGN(newsize);
>   
>       if (block->used_length == newsize) {
> +        /*
> +         * We don't have to resize the ram block (which only knows aligned
> +         * sizes), however, we have to notify if the unaligned size changed.
> +         */
> +        if (unaligned_size != memory_region_size(block->mr)) {
> +            memory_region_set_size(block->mr, unaligned_size);
> +            if (block->resized) {
> +                block->resized(block->idstr, unaligned_size, block->host);
> +            }
> +        }
>           return 0;
>       }
>   
> @@ -2102,9 +2114,9 @@ int qemu_ram_resize(RAMBlock *block, ram_addr_t newsize, Error **errp)
>       block->used_length = newsize;
>       cpu_physical_memory_set_dirty_range(block->offset, block->used_length,
>                                           DIRTY_CLIENTS_ALL);
> -    memory_region_set_size(block->mr, newsize);
> +    memory_region_set_size(block->mr, unaligned_size);
>       if (block->resized) {
> -        block->resized(block->idstr, newsize, block->host);
> +        block->resized(block->idstr, unaligned_size, block->host);
>       }
>       return 0;
>   }
>