Re: [Xen-devel] [PATCH] libxl: fix assertion failure in stub domain creation

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Wed, Feb 05, 2020 at 09:37:24AM +0000, Paul Durrant wrote:
> An assertion in libxl__domain_make():
> 
> 'soft_reset || *domid == INVALID_DOMID'
> 
> does not hold true for stub domain creation, where soft_reset is false
> but the passed in domid == 0. This is easily fixed by changing the
> initializer in libxl__spawn_stub_dm().
> 
> Fixes: 75259239d85d ("libxl_create: make 'soft reset' explicit")
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> ---
>  tools/libxl/libxl_dm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> index f758daf3b6..3b1da90167 100644
> --- a/tools/libxl/libxl_dm.c
> +++ b/tools/libxl/libxl_dm.c
> @@ -2127,7 +2127,7 @@ void libxl__spawn_stub_dm(libxl__egc *egc, 
> libxl__stub_dm_spawn_state *sdss)
>          goto out;
>      }
>  
> -    sdss->pvqemu.guest_domid = 0;
> +    sdss->pvqemu.guest_domid = INVALID_DOMID;

How this works? INVALID_DOMID seems to be directly feed to
xc_domain_create(), which is using XEN_DOMCTL_createdomain.
But a comment in domctl.h for XEN_DOMCTL_createdomain read:
    NB. xen_domctl.domain is an IN/OUT parameter for this operation.
    If it is specified as zero, an id is auto-allocated and returned.
So, is xc_domain_create going to create a new domain with
domid==INVALID_DOMID?

Thanks,

-- 
Anthony PERARD

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