Re: [Qemu-devel] [PATCH] add MADV_DONTFORK to guest physical memory

[Andreas Färber]

Am 15.09.2010 um 19:08 schrieb Andrea Arcangeli:

> From: Andrea Arcangeli <address@hidden>
>
> All allocated guest physical memory shall be marked MADV_DONTFORK,  
> otherwise
> fork will fail because of accounting issues preventing migration or  
> netdev_add
> when the guest allocated more than half of host physical memory.
>
> Signed-off-by: Andrea Arcangeli <address@hidden>
> ---
>
> diff --git a/exec.c b/exec.c
> index 380dab5..e2bdf19 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2861,6 +2861,9 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState  
> *dev, const char *name,
> #ifdef MADV_MERGEABLE
>             madvise(new_block->host, size, MADV_MERGEABLE);
> #endif
> +#ifdef MADV_DONTFORK
> +            madvise(new_block->host, size, MADV_DONTFORK);
> +#endif

There is a pending patch which introduces qemu_madvise() and will  
eliminate the need for these #ifdefs, which was demanded by Blue. I'll  
cc you on v6.

Regards,

Andreas