Re: [Xen-devel] [PATCH] x86/shadow: don't enable shadow mode with too small a shadow allocation (part 2)

[Tim Deegan <tim@xxxxxxx>]

At 09:55 +0200 on 04 Sep (1567590940), Jan Beulich wrote:
> Commit 2634b997af ("x86/shadow: don't enable shadow mode with too small
> a shadow allocation") was incomplete: The adjustment done there to
> shadow_enable() is also needed in shadow_one_bit_enable(). The (new)
> problem report was (apparently) a failed PV guest migration followed by
> another migration attempt for that same guest. Disabling log-dirty mode
> after the first one had left a couple of shadow pages allocated (perhaps
> something that also wants fixing), and hence the second enabling of
> log-dirty mode wouldn't have allocated anything further.
> 
> Reported-by: James Wang <jnwang@xxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Tim Deegan <tim@xxxxxxx>

> --- a/xen/arch/x86/mm/shadow/common.c
> +++ b/xen/arch/x86/mm/shadow/common.c
> @@ -2864,7 +2864,8 @@ static int shadow_one_bit_enable(struct
>  
>      mode |= PG_SH_enable;
>  
> -    if ( d->arch.paging.shadow.total_pages == 0 )
> +    if ( d->arch.paging.shadow.total_pages <
> +         sh_min_allocation(d) + d->arch.paging.shadow.p2m_pages )
>      {
>          /* Init the shadow memory allocation if the user hasn't done so */
>          if ( shadow_set_allocation(d, 1, NULL) != 0 )

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