Re: [Xen-devel] [PATCH] xenpaging:add the dealing of MEM_EVENT_FLAG_EVICT_FAIL request in

[Olaf Hering <olaf@xxxxxxxxx>]

On Thu, Feb 09, hongkaixing@xxxxxxxxxx wrote:

> xenpaging:add the dealing of MEM_EVENT_FLAG_EVICT_FAIL request in
> tools/xenpaging
> 
> If a page is nominated but not evicted,then dom0 accesses the page,it
> will change the page's p2mt to be p2m_ram_paging_in,and the req.flags is
> MEM_EVENT_FLAG_EVICT_FAIL;so it will fail in p2m_mem_paging_evict() because
> of the p2mt;and paging->num_paged_out will not increase in this case;After
> the paging process is terminated, the p2mt p2m_ram_paging_in still remains
> in p2m table.Once domU accesses the nominated page,it will result in BSOD
> or vm'stuck.
> The patch adds the dealing of this request to resume the page before xenpaging
> is ended.

This can happen if p2m_mem_paging_populate() was called by a foreign
domain. In this case MEM_EVENT_FLAG_VCPU_PAUSED is not set and xenpaging
will not sent a response. And in this case the ring is in an
inconsistent state anyway, new requests cant be added, I think.


Acked-by: Olaf Hering <olaf@xxxxxxxxx>

> Signed-off-by??hongkaixing<hongkaixing@xxxxxxxxxx>,shizhen<bicky.shi@xxxxxxxxxx>
> 
> diff -r 9f4640e40d4f -r 68eae0b487ae tools/xenpaging/xenpaging.c
> --- a/tools/xenpaging/xenpaging.c     Thu Feb 09 16:50:52 2012 +0800
> +++ b/tools/xenpaging/xenpaging.c     Thu Feb 09 16:58:01 2012 +0800
> @@ -911,7 +911,7 @@
>                          !!(req.flags & MEM_EVENT_FLAG_EVICT_FAIL) );
>  
>                  /* Tell Xen to resume the vcpu */
> -                if ( req.flags & MEM_EVENT_FLAG_VCPU_PAUSED )
> +                if (( req.flags & MEM_EVENT_FLAG_VCPU_PAUSED ) || ( 
> req.flags & MEM_EVENT_FLAG_EVICT_FAIL ))
>                  {
>                      /* Prepare the response */
>                      rsp.gfn = req.gfn;

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