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

Re: [Xen-devel] [PATCH] IOMMU/x86: per-domain control structure is not HVM-specific

On 03/05/16 11:18, Andrew Cooper wrote:
On 03/05/16 10:59, Jan Beulich wrote:
On 03.05.16 at 11:36, <andrew.cooper3@xxxxxxxxxx> wrote:
On 02/05/16 13:55, Jan Beulich wrote:
... and hence should not live in the HVM part of the PV/HVM union. In
fact it's not even architecture specific (there already is a per-arch
extension type to it), so it gets moved out right to common struct

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Yikes - this really does need fixing ASAP.
The more interesting question here is how to deal with the stable
trees: The patch, due to its size, doesn't really lend itself to
backporting. Yet the alternative (mentioned in a remark in the
original submission) would be pretty clumsy too.


Once the structure layout has moved, the compiler (and/or grep) will
highlight all the other uses.

In this instance, I would be tempted to suggest that we just do a custom
backport for each stable tree.

The only thing a BUILD_BUG_ON() will do is force someone else to
backport this patch if it actually triggers.

It will, however, avoid the code churn to the stable trees if (as expected) the BUILD_BUG_ON() does *not* trigger.

I think both are reasonable approaches. I find it hard to imagine how new bugs could be introduced by moving the structure; the main risk would be that it exposes latent bugs. But there's an equal probability that there are latent bugs with the current layout.

Doing a more complete backport may make future bug fixes which touch this code easier to backport as well.


Xen-devel mailing list



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