Re: kvm: make --mem-path memory allocation depend on mmu notifiers

["David S. Ahern" <daahern@cisco.com>]

Marcelo Tosatti wrote:
> Without mmu notifiers usage of hugepages to back guest memory can cause
> memory corruption.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> 
> diff --git a/qemu/vl.c b/qemu/vl.c
> index d0660ab..49cf066 100644
> --- a/qemu/vl.c
> +++ b/qemu/vl.c
> @@ -4664,6 +4664,11 @@ void *alloc_mem_area(size_t memory, unsigned long *len, const char *path)
>      void *area;
>      int fd;
>  
> +    if (!kvm_has_sync_mmu()) {
> +        fprintf(stderr, "host lacks mmu notifiers, disabling --mem-path\n");
> +        return NULL;
> +    }
> +
>      if (asprintf(&filename, "%s/kvm.XXXXXX", path) == -1)
>  	return NULL;
>  

That means you can't use hugepages with RHEL5 as the host OS. That's not
good for me. I've exclusively used hugepages for the past 6 months or
so, the past 2 months with RHEL5 as the host OS without a problem. How
likely is it to occur (theoretically possible or random selection)?

david


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