Xen devel - Oct 2012 - Re: about the patch: persistent grant maps for xen blk drivers

On Mon, Oct 15, 2012 at 01:01:51PM +0800, liuxiaolei1124
wrote:
> Dear konrad:
>    i have seen you put the patch "persisten grant maps for xen blk
drivers" into you kernel, then dom0 crash
.(https://lkml.org/lkml/2012/9/21/388 )my dom0 kernel is 2.6.32.36-0.5, and i
put this patch in my kernel, there is a bug too, and the stack is much like
yours. And i found  a strange phenomenon. when i add a printk log  such as
"printk ("enter func") " in blkif_completion or other
function in xen-blkfront.c, guest run well. But after i remove this printk log,
guest crash when i start.

Hey. Roger posted a follow up patch that has this fixed. You should
look at that.

Also CC-ing xen-devel here.
>     and the crash stack is :
>     blkif_int -> blkif_completion
>     guest page fault in
>  
> + if (bret->operation == BLKIF_OP_READ)
> + rq_for_each_segment(bvec, s->request, iter) {
> + shared_data = kmap_atomic
> +                                            
(pfn_to_page(s->grants_used[i++]->frame));  // page fault
> + bvec_data = bvec_kmap_irq(bvec, &flags);
> + memcpy(bvec_data, shared_data + bvec->bv_offset,
> +        bvec->bv_len);
> + bvec_kunmap_irq(bvec_data, &flags);
> + kunmap_atomic(shared_data);
> + }
> 
> in kernel 2.6.32.36-0.5, my patch is :
>  
> + if (bret->operation == BLKIF_OP_READ)
> + rq_for_each_segment(bvec, s->request, iter) {
> + shared_data = kmap_atomic
> + (pfn_to_page(s->grants_used[i++]->frame), KM_USER0);
> + bvec_data = bvec_kmap_irq(bvec, &flags);
> + memcpy(bvec_data, shared_data + bvec->bv_offset,
> +        bvec->bv_len);
> + bvec_kunmap_irq(bvec_data, &flags);
> + kunmap_atomic(shared_data, KM_USER0);
> + }
> 
>    I don''t know what''s wrong? mybe function kmap_atomic
in my patch is incorrect. I look forward toyour reply, thank you.
>  
>   Best wishes.
>   eric.liu
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At 2012-10-15 21:19:30,"Konrad Rzeszutek Wilk"
<konrad.wilk@oracle.com> wrote:
>On Mon, Oct 15, 2012 at 01:01:51PM +0800, liuxiaolei1124 wrote:
>> Dear konrad:
>>    i have seen you put the patch "persisten grant maps for xen blk
drivers" into you kernel, then dom0 crash
.(https://lkml.org/lkml/2012/9/21/388 )my dom0 kernel is 2.6.32.36-0.5, and i
put this patch in my kernel, there is a bug too, and the stack is much like
yours. And i found  a strange phenomenon. when i add a printk log  such as
"printk ("enter func") " in blkif_completion or other
function in xen-blkfront.c, guest run well. But after i remove this printk log,
guest crash when i start.
>
>
>Hey. Roger posted a follow up patch that has this fixed. You should
>look at that.
sorry, but i can''t find the patch Roger posted, could you show me the
link of the patch? thank you.
Best wishes.
eric.liu


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On Tue, Oct 16, 2012 at 12:35:23PM +0800, liuxiaolei1124
wrote:
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> At 2012-10-15 21:19:30,"Konrad Rzeszutek Wilk"
<konrad.wilk@oracle.com> wrote:
> >On Mon, Oct 15, 2012 at 01:01:51PM +0800, liuxiaolei1124 wrote:
> >> Dear konrad:
> >>    i have seen you put the patch "persisten grant maps for
xen blk drivers" into you kernel, then dom0 crash
.(https://lkml.org/lkml/2012/9/21/388 )my dom0 kernel is 2.6.32.36-0.5, and i
put this patch in my kernel, there is a bug too, and the stack is much like
yours. And i found  a strange phenomenon. when i add a printk log  such as
"printk ("enter func") " in blkif_completion or other
function in xen-blkfront.c, guest run well. But after i remove this printk log,
guest crash when i start.
> >
> >
> >Hey. Roger posted a follow up patch that has this fixed. You should
> >look at that.
> sorry, but i can''t find the patch Roger posted, could you show me
the link of the patch? thank you.
Roger, could you repost them please?
> Best wishes.
> eric.liu