Re: about the patch: persistent grant maps for xen blk drivers

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

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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