Re: [Qemu-devel] [PATCH v1 08/17] migration: add helpers to change VM memory protection rights

[Dr. David Alan Gilbert]

* Denis Plotnikov (address@hidden) wrote:
> Signed-off-by: Denis Plotnikov <address@hidden>
> ---
>  migration/ram.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
>  migration/ram.h |  3 +++
>  2 files changed, 57 insertions(+)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 27d3403435..ce3dead932 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1555,6 +1555,60 @@ void ram_block_list_destroy(void)
>      }
>  }
>  
> +static int mem_protect(void *addr, uint64_t length, int prot)
> +{
> +    int ret = mprotect(addr, length, prot);
> +
> +    if (ret < 0) {
> +        error_report("%s: Can't change protection on ram block at %p",
> +                     __func__, addr);
> +    }
> +
> +    return ret;
> +}
> +
> +static int ram_set_ro(void *addr, uint64_t length)
> +{
> +    return mem_protect(addr, length, PROT_READ);
> +}
> +
> +static int ram_set_rw(void *addr, uint64_t length)
> +{
> +    return mem_protect(addr, length, PROT_READ | PROT_WRITE);
> +}
> +
> +int ram_block_list_set_readonly(void)
> +{
> +    RAMBlock *block = NULL;
> +    RamBlockList *block_list = ram_bgs_block_list_get();
> +    int ret = 0;
> +
> +    QLIST_FOREACH(block, block_list, bgs_next) {
> +        ret = ram_set_ro(block->host, block->used_length);
> +        if (ret) {
> +            break;
> +        }
> +    }
> +
> +    return ret;
> +}
> +
> +int ram_block_list_set_writable(void)
> +{
> +    RAMBlock *block = NULL;
> +    RamBlockList *block_list = ram_bgs_block_list_get();
> +    int ret = 0;
> +
> +    QLIST_FOREACH(block, block_list, bgs_next) {
> +        ret = ram_set_rw(block->host, block->used_length);
> +        if (ret) {
> +            break;
> +        }
> +    }

Do you need to keep track of who was writeable previously
to avoid changing blocks that should be read-only, 
Or are all RAMBlocks currently mapped rw?

Dave

> +    return ret;
> +}
> +
>  static void ram_page_buffer_decrease_used(void)
>  {
>      qemu_event_reset(&ram_state->page_buffer.used_decreased);
> diff --git a/migration/ram.h b/migration/ram.h
> index 7c802c1d7f..4c463597a5 100644
> --- a/migration/ram.h
> +++ b/migration/ram.h
> @@ -71,4 +71,7 @@ RAMBlock *ram_bgs_block_find(uint8_t *address, ram_addr_t 
> *page_offset);
>  void *ram_page_buffer_get(void);
>  int ram_page_buffer_free(void *buffer);
>  
> +int ram_block_list_set_readonly(void);
> +int ram_block_list_set_writable(void);
> +
>  #endif
> -- 
> 2.17.0
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK