Re: [PATCH] hw/i386/pc: when adding reserved E820 entries do not allocate dynamic entries

[Igor Mammedov]

On Thu, 10 Feb 2022 18:58:21 +0530
Ani Sinha <ani@anisinha.ca> wrote:

> When adding E820_RESERVED entries we also accidentally allocate dynamic
> entries. This is incorrect. We should simply return early with the count of
> the number of reserved entries added.

can you expand commit message to explain what's wrong and
how problem manifests ... etc.

> 
> fixes: 7d67110f2d9a6("pc: add etc/e820 fw_cfg file")
> cc: kraxel@redhat.com
> Signed-off-by: Ani Sinha <ani@anisinha.ca>
> ---
>  hw/i386/e820_memory_layout.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/hw/i386/e820_memory_layout.c b/hw/i386/e820_memory_layout.c
> index bcf9eaf837..afb08253a4 100644
> --- a/hw/i386/e820_memory_layout.c
> +++ b/hw/i386/e820_memory_layout.c
> @@ -31,6 +31,8 @@ int e820_add_entry(uint64_t address, uint64_t length, 
> uint32_t type)
>          entry->type = cpu_to_le32(type);
>  
>          e820_reserve.count = cpu_to_le32(index);
> +
> +        return index;
>      }

this changes e820_table size/content, which is added by fw_cfg_add_file() to 
fwcfg,
as result it breaks ABI in case of migration.
>  
>      /* new "etc/e820" file -- include ram too */