On Tue, Jul 07, 2015 at 06:36:53PM +0200, Thomas Huth wrote: > On Thu, 2 Jul 2015 11:32:52 +0200 > "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > On Thu, Jul 02, 2015 at 11:12:56AM +0200, Greg Kurz wrote: > > > On Thu, 2 Jul 2015 08:01:28 +0200 > > > "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > ... > > > > Yea, well - support for legacy BE guests on the new LE hosts is > > > > exactly the motivation for this. > > > > > > > > I dislike it too, but there are two redeeming properties that > > > > made me merge this: > > > > > > > > 1. It's a trivial amount of code: since we wrap host/guest accesses > > > > anyway, almost all of it is well hidden from drivers. > > > > > > > > 2. Sane platforms would never set flags like VHOST_CROSS_ENDIAN_LEGACY - > > > > and when it's clear, there's zero overhead (as some point it was > > > > tested by compiling with and without the patches, got the same > > > > stripped binary). > > > > > > > > Maybe we could create a Kconfig symbol to enforce point (2): prevent > > > > people from enabling it e.g. on x86. I will look into this - but it can > > > > be done by a patch on top, so I think this can be merged as is. > > > > > > > > > > This cross-endian *oddity* is targeting PowerPC book3s_64 processors... I > > > am not aware of any other users. Maybe create a symbol that would > > > be only selected by PPC_BOOK3S_64 ? > > > > I think some ARM systems are trying to support cross-endian > > configurations as well. > > > > Besides that, yes, this is more or less what I had in mind. > > Would something simple like this already do the job: > > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig > --- a/drivers/vhost/Kconfig > +++ b/drivers/vhost/Kconfig > @@ -35,6 +35,7 @@ config VHOST > > config VHOST_CROSS_ENDIAN_LEGACY > bool "Cross-endian support for vhost" > + depends on KVM_BOOK3S_64 || KVM_ARM_HOST > default n > ---help--- > This option allows vhost to support guests with a different byte > > ? Do all ARM hosts support this dynamic endian-ness? > If that looks acceptable, I can submit a proper patch if you like. > > Thomas I think I prefer some kind of symbol defined by these arches, so I don't get to maintain an arch list in vhost. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
