[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Grant unmap error checking in Dom0

On Tue, Mar 18, 2014 at 01:21:18PM +0000, Zoltan Kiss wrote:
> Hi,
> Just out of curiosity I've checked how Dom0 handles errors during
> grant unmapping. Usually there is a BUG_ON(ret) for the return value
> of gnttab_unmap_refs in blkback and netback, gntdev drops just a
> The return value can be non-zero only if Xen failed to copy the map
> operations back and forth to the guest supplied memory, so it's
> reasonable to crash there. However I'm wondering why gntdev is happy
> with just a WARN.
> Another thing, we don't check the status of the operations if the
> return value is zero. We shouldn't normally do that, Xen logs info
> messages in some cases, but not always (e.g. XSM or IOMMU problems).
> For debugging purposes however it could be useful to have the
> ability to turn on checking in Dom0. A quick and dirty way to do
> this is to use printk_get_level to figure out if the loglevel is
> e.g. KERN_NOTICE or lower, but I'm sure there is a better way to do
> this :) It would be an overkill to introduce new config option, I'm
> thinking a runtime parameter to check in an unlikely(), so it won't
> cause performance penalty for normal operation. Any opinions on
> that?

One can always just have printk(KERN_DEBUG and if the user did not
boot with 'debug' the messages go to /dev/null.

> Zoli
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.