[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC 00/23] arm64: Add support for 64KB page granularity in Xen guest
On Tue, 23 Jun 2015, Stefano Stabellini wrote: > On Mon, 18 May 2015, Julien Grall wrote: > > Hi David, > > > > On 15/05/15 16:45, David Vrabel wrote: > > > On 14/05/15 18:00, Julien Grall wrote: > > >> Hi all, > > >> > > >> ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, > > >> Xen > > >> hypercall interface and PV protocol are always based on 4KB page > > >> granularity. > > >> > > >> Any attempt to boot a Linux guest with 64KB pages enabled will result to > > >> a > > >> guest crash. > > >> > > >> This series is a first attempt to allow those Linux running with the > > >> current > > >> hypercall interface and PV protocol. > > >> > > >> This solution has been chosen because we want to run Linux 64KB in > > >> released > > >> Xen ARM version or/and platform using an old version of Linux DOM0. > > > > > > The key problem I see with this approach is the confusion between guest > > > page size and Xen page size. This is going to be particularly > > > problematic since the majority of development/usage will remain on x86 > > > where PAGE_SIZE == XEN_PAGE_SIZE. > > > > > > I think it would be nice to keep XEN_PAGE_SIZE etc out of front and > > > backend drivers. Perhaps with a suitable set of helper functions? > > > > Even with the helpers, we are not protected from any change in the > > frontend/backend that will impact 64K. It won't be possible to remove > > all the XEN_PAGE_* usage (there is a lots of places where adding helpers > > would not be possible) and we would still have to carefully review any > > changes. > > We could at least introduce a few asserts, so that an ARM64 kernel > build, that any x86 maintainers can easily and quickly do on their x86 > machines, would spot these errors. I actually meant BUILD_BUG_ON _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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